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Original Review Date: January 31, 1999 |
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High-end "personal" film scanner |
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2820 dpi resolution (32.5 meg file from 35mm neg!) | |
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12 bits per channel, 3.6 Dmax specification | |
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High-speed SCSI interface (card included | |
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Software accommodates beginners AND experts | |
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Optional APS adapter |
Overview
Minolta is a company with long experience in the world of film,
and extensive digital expertise that has so far been applied
primarily in the areas of office electronics and imaging (copiers
& printers). Recently though, they've been making significant
waves in the digital camera and scanner markets, with their highly
capable (and expandable!) Dimage EX 1500 Zoom digital camera,
and a whole line of film scanners covering everything from APS
to 35mm, to medium-format photography. We'll be reviewing the
full range of the Dimage scanners, beginning with the Dimage
Scan Speed that's the subject of this review.
The Minolta Dimage Scan Speed film scanner is quite a bit more
capable than some of the "personal" film scanners we've
reviewed in the past, positioned at the upper end of the "enthusiast"
market with a list price as of this writing of $1,299. In many
respects, its capabilities reach into the lower end of the "professional"
market. We see it fitting the needs of users ranging from well-heeled
photo enthusiasts, to businesses and professional photographers
looking for top performance on a budget. In support of this market,
we found the Dimage software did a particularly good job of providing
the power demanded by pros, while remaining very approachable
for the amateur.
"High Points" Overview
- 12-bit digitization, 3.6 Dmax
- 2820 dpi resolution
- User interface accommodates both beginners and experienced users
- "Preview" function can pre-scan entire APS film roll
- Cold-cathode light source for long bulb life
EZ-Print Page
In response to reader requests, we now provide copies of all
reviews stripped of all their formatting, to faciliate printing.
Click here to go to the EZ-Print
page.
The Basics
The Dimage Scan Speed is a desktop device about the size of a
hefty novel standing on edge. (The long side down.) It measures
3.6 x 6.3 x 10.7 inches (90.5 x 160.5 x 272 mm), and weighs about
4.4 pounds (2 kg). Interface to the host computer is via a high-speed
SCSI-2 interface, meaning you'll need to have such a port installed
in your computer to use it. (Macs typically come equipped with
SCSI connections: On a Windows machine, you'll need to have an
interface card installed. Appropriate cards range from $100 to
$300 in price. The manual lists a number of Adaptec SCSI cards
from the 1500 and 2900 series that are suitable. The only restriction
seems to be that the 1500-series boards don't work with NEC PC98xx
computers.) The standard unit can scan 35mm negatives or slides,
in either black and white or color. An optional APS adapter is
available for scanning that film type.
The software CD shipped with the unit supports both Mac and Windows
platforms. Standalone scanning applications are provided for
both platforms, as well as a Photoshop acquire plug-in for the
Mac, and TWAIN drivers for the PC. (NOTE: Minolta specifies that
the scanner requires either Windows '95 release 2 (OSR2), or
Windows '98. If you're running Windows '95, be sure to check
the revision level you have installed.)
Scanning resolution can be as high as 2820 dpi (a 2700-element
CCD covering the width of a 35mm slide or negative). This produces
maximum image sizes of 2688x4032 pixels for 35mm (32.5 megabytes),
or 1920x3328 for APS (19.2 megabytes).
A note about scanner resolution, as compared to that of digital
cameras: The 10.8 megapixel resolution of the Dimage Scan Speed
is even higher than you might expect, when compared to the resolution
of a digital camera. Because the scanner's CCD samples each pixel
in all three red, green, and blue color channels, it's really
equivalent to a digital camera with a 32 megapixel sensor and
"striped" color filters. Thus, the first thing most
people notice about images scanned from negatives and slides
is the extraordinary level of detail captured. That said, the
Dimage Scan Speed's scan resolution of 2820 dpi is at the top
of the field for 35mm/APS scanners.
Another important scanning parameter is "bit depth,"
a measure of both color accuracy and the maximum density range
the scanner can recognize. (8 bits per channel is good, 10 better,
and 12 the best you'll commonly find in desktop scanners.) The
Dimage Scan Speed captures a full 12 bits per pixel.
Scanner Optics & Light Path
Film scanners tend to take one of two approaches in their optical
design, providing either fixed or adjustable focus. The Dimage
Scan Speed employs fixed-focus optics. Given the extreme resolution
of most film scanners, we're surprised that the lenses can be
designed with enough depth of field to insure sharp focus in
the face of minor variations in the film plane position. We're
surprised, but the fixed-focus approach nonetheless seems to
work quite well, as evidenced by the performance of the Dimage
Scan Speed. The upside of fixed-focus designs of course, is that
you don't have to worry about focusing, either in the form of
twiddling a thumbwheel, or by waiting while the scanner adjusts
its focus for every scan. In our testing, the Dimage Scan Speed
produced sharp images every time, the sole exclusion being one
orientation of our unusual "USAF 1951" resolution target,
which is a glass slide with the pattern deposited on one side
of it. With the pattern facing one way, we got sharp results,
but decidedly blurry ones with it facing the other. We saw no
evident focus deficiencies while scanning normal slides or negatives.
The Dimage Scan Speed uses a special fluorescent light source,
producing strong spectral peaks in the red, green, and blue portions
of the spectrum. We observed that this diffuse illumination source
produced somewhat "softer" scans than some other scanners.
The resulting scans had less of a razors-edge on fine detail,
but were also much more forgiving of film defects and film grain.
A good analogy (for those old darkroom aficionados out there)
would be the difference between condenser and diffusion enlargers:
The condenser optics tend to produce sharper images, but at the
cost of greatly enhanced grain, while diffusion enlargers create
a softer look. Note in this though, that while the scans produced
by the Dimage Scan Speed have a somewhat "softer" appearance
to them, they in fact appear to carry an extremely high level
of detail, as evidenced by the results from our WG-18 (ISO-12233)
resolution target scans.
Film Handling
The Dimage Scan Speed uses plastic slide- and filmstrip-holders
to carry the film to the scanner: You first place the media to
be scanned into the holder, then insert the holder into the scanner.
The holders have detent notches on them that provide repeatable
film positioning, and yet allow for manual advance of the film
between frames. During scanning, the holder and film is moved
past a fixed CCD array. The filmstrip holder can accommodate
strips of 35mm film up to six frames in length, and the slide
holder up to four slides. Both holders are reversible, a necessary
feature for their use: Inserted into the scanner, you can access
half of the total film frames by sliding the adapter in or out.
To reach the remaining frames, you remove the adapter, flip it
end for end, and reinsert it.
We found both the slide and film holders to be quite effective
and easy to use. The film adapter is hinged, but only to the
extent that a plate flips up to expose the recess into which
the film is laid. (Unlike many "clamshell" designs,
the slot holding the film is a fixed structure.) The back pressure
plate then hinges back down and latches, clamping the film flat.
This arrangement did a particularly good job of handling curled
or damaged film, regardless of whether the film was curled side-to-side,
or along its length. The film-holding slot is about a half-millimeter
wider than the film itself, doing a good job of constraining
the film position, yet still allowing minor adjustments to be
made for fine alignment relative to the limits of the scanning
area. We did find that the filmstrip holder crops the 35mm frame
very slightly, about 3% in both vertical and horizontal directions
by our reckoning. (For some reason, this appears to be a common
characteristic of strip-film holders.)
The slide holder is also constructed of plastic, with four slots
along the top edge into which the slides may be loaded. The edges
of each slot set absolute limits for the horizontal position
of the slide mount, but there's a bit more play (about a full
millimeter side-to-side) with slides than is present in the filmstrip
adapter. This is probably a good thing, as it allows you to correct
for film misaligned in its mount: You can manually tweak the
slides to achieve about two degrees of rotation in either direction,
as needed. (Despite this looseness, we had no difficulty aligning
slides square to the holder, as the edges of the "windows"
in the holder provided good reference surfaces to align to, and
simply "bottoming out" the slide in the slot yielded
good alignment if the film was properly positioned in the slide
mount.) The slide holder is also a little unusual in the way
that the slides "float" between two sets of spring-loaded
fingers. This seemed to do a good job of keeping the film plane
well-centered about the point of optimum focus. The centering
fingers gripped a particularly thick plastic-and-glass slide
mount quite a bit more firmly than they did standard cardboard
ones, but handled a wide range of mounts well.
System Interface and Included Software
The Dimage Scan Speed uses a SCSI-2 connection to the host computer,
providing the high speed data transfer necessary to handle the
large amounts of data the scanner can generate. No SCSI card
is included with the unit, but Minolta lists several models of
Adaptec cards that the unit can be used with. (Adaptec is pretty
much the standard for SCSI cards: You can find cheaper ones,
but the Adaptec models are more likely to be compatible with
a wide range of equipment. Note in particular, that some scanners,
CD-ROM drives, and other equipment ships with low-cost SCSI cards
included. In many cases, these are "dedicated" cards,
that will only run the particular device they're shipped with.
If you're buying a card to support the Dimage Scan Speed, take
our advice and get a "name brand" Adaptec unit. The
hassle you'll save will be more than worth it!)
Once connected to the computer, the Dimage Scan Speed is controlled
through an excellent software interface that we'll describe in
greater detail below. As noted earlier, the scanner-control software
takes the form of standalone applications on both the Mac and
PC, as well as a Photoshop plug-in on the Mac, and a TWAIN component
on the PC. A particular strength of the Dimage software is the
extent to which it provides powerful controls for experienced
users, while at the same time offering a simple interface for
novices.
A nice touch in the Dimage Scan Speed package was the inclusion
of Adobe's Photoshop LE, for both Mac and Windows. Photoshop
LE is a slightly trimmed-down version of the full Photoshop package,
the primary omissions being support for color spaces other than
RGB (such as CMYK, for commercial offset printing), and less
in the way of color management. At one time, it was quite common
to find Photoshop LE or even a full version of Photoshop bundled
with many scanning devices. The combination of policy changes
at Adobe (implemented in the form of radically higher prices
to their bundling partners), and ever-tightening margins and
declining retail prices in the scanner market have all but eliminated
Photoshop from the "bundle" market. We applaud Minolta's
inclusion of this program with the Dimage Scan Speed though:
We suspect that many potential purchasers of the Scan Speed will
be upgrading their imaging capability with the acquisition, and
won't already have a copy of Photoshop. While trimmed-down somewhat
from the capabilities of the full version, Photoshop LE is a
dramatic step up from the "dumbed-down" interface and
capabilities of Adobe's PhotoDeluxe, a much more common software
bundle component these days. Don't get us wrong, PhotoDeluxe
is an excellent program, but is clearly targeted at the casual
user. Even at that though, we've long felt that removing key
features such as the "levels" control is no gift to
the end-user. While it may make the program easier to use, such
simplification ultimately leaves users at a dead end, with nowhere
to go as their skills and abilities improve. Photoshop LE is
adequate to the needs of most semi-pro users, and will provide
the full range of capabilities that most users will need to achieve
the best results. Flame off for now, but repeated kudos to Minolta
for taking the cost hit and including Photoshop LE with the scanner.
One parting shot: You can't buy Photoshop LE, only the full version
of Photoshop, which routinely sells for well over $500. Given
that the LE version will be enough for the majority of users,
the argument could be made that its inclusion in the Dimage Scan
Speed bundle will save many people $500 or more. This fact alone
is a significant differentiator for the Minolta's product.
Speeds and Feeds
As its name suggests, the Dimage Scan Speed is intended to be
a fast scanner. In our testing, we found that it did indeed zip
along pretty quickly. This appeared to be due partly to the basic
mechanism and electronics (which moves the film and digests the
data rapidly), and partly to the fixed-focus optics: When you
tell the unit to begin scanning, there's no delay for focus adjustment
before the scan starts. The unit does make one pass over the
negative or slide first though, to determine an autoexposure
level, a process that takes 4-5 seconds. Scanning throughput
was quite good with the unit, helped by the flexible, easy-to-use
software, but also by the fast scan times themselves. (We haven't
in the past explicitly measured preview and scan times, so won't
have comparable numbers for many scanners we've previously tested.
From this point on though, we'll begin measuring these throughput-related
timings on a routine basis...) Running the Dimage Scan Speed
from an Adaptec SCSI card on our 350 MHz Pentium-II Windows machine,
we measured the following scan times:
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Preview w/autoexposure: |
20 seconds |
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Preview w/o autoexposure: |
16 seconds |
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Low res (~600dpi) full-frame scan: |
21 seconds |
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Full res (2820 dpi) full-frame scan: |
44 seconds |
Operation and User Interface
Other than the actual scans themselves, most of the story to
be told about a film scanner has to do with the software that
drives it, and to what extent the combination of hardware and
software makes it easy to produce good-quality scans. Accordingly,
we'll devote a sizable of this review to talking about the software
that drives Minolta's Dimage family of scanners, and the Dimage
Scan Speed in particular.
As noted several times already, we feel that Minolta has done
a particularly good job of balancing capability with ease-of-use.
This is a difficult equation to optimize, as the needs of "beginners"
and "experts" can vary so widely. At the same time,
the goal should be to provide a smooth gradation of capability,
not introducing any abrupt hurdles to overcome as the users advance
in their sophistication. Minolta has accomplished this difficult
design goal by providing very basic, visually-oriented contrast/brightness
adjustments for neophytes, while at the same time offering fairly
sophisticated histogram and tone curve controls for those comfortable
with more complex adjustments, and who need the control they
provide.
As we write this, we're still searching for our "formula"
that works best for scanner reviews, but are generally settling
on a format in which we step through the scanner controls in
the approximate order that a user would encounter them. (For
a more complete walk-through of scanner operation, check out
Minolta's
excellent web site for their scanners: They've put together
a comprehensive "on-line demo" of how the software
works.)
The Preview Screen and Command Window
The most basic options and functions of the Dimage Scan Speed
scanner are controlled via the Command window, shown below. The
Command window contains two list boxes, two status displays,
and a total of ten buttons, which we describe below, moving from
left to right, top to bottom in the screen shot: (NOTE: This
and all screen shots following have been scaled-down to better
fit the 'web page -- The actual screens are larger and much more
readable!)
- Film Format (List Box) - Options are 35mm or APS
- Film Type (List Box) - Options are Slide Film, Color
Negative, B/W Negative, B/W Positive
- Current Job Selection (Display window) - Displays
currently-chosen "job type", combining both input and
output resolutions. (Translating input resolution (at the film)
to output resolution (in the file and on paper when printed)
is a tough process to make understandable: Minolta's "Job
Type" approach does as good a job of this as any approach
we've seen thus far.)
- Job Selection Button - Click for a pop-up menu of
currently-defined job types, or create your own.
- Status Bar (Display field) - Displays descriptions
of controls as your mouse rolls over them, and gives status information
during the scan process. (Very handy for interpreting the sometimes-cryptic
button icons, before you get used to them.)
- Index Scan Button (APS Only) - Creates thumbnail-sized
index scans of an entire APS film roll.
- Prescan Button (APS or 35mm) - Generates a preview
scan of the current film frame or slide. Preview scan sizes can
be set to large, small, or automatic. Auto fits the scan resolution
to the size screen you're working on. Generally, you'll want
the largest preview scan you can get, to help in accurately setting
white and black points and in adjusting the tone curves.
Scan Settings Button -
Brings up the Scan Settings window (shown at right), where you
can manually adjust the input and output scan resolutions and
set the units you want to work in (pixels, inches, or cm). NOTE
that you can't set the resolution values when your units are
set to pixels, as in the screenshot at right.
- Save Index Scan Button - To save time on subsequent
scans (as well as provide a useful index of images on your APS
rolls), you can save APS index scans to disk.
- Save Job Button - If you've created a custom Scan
Settings configuration, you can save it under its own "job
type," for immediate recall later.
- Preferences Button - Brings up the Preferences window,
described later.
- Rewind Button (APS Only) - Rewinds APS film back into its canister.
- Help - (If you need us to explain what this button
does, you probably shouldn't buy the scanner! ;-)
Preferences Window
The preferences window (not shown) controls a number of overall settings
governing scanner operation. Most people will rarely need to
visit this screen, as the default settings will suffice for many
applications. About the only control you're likely to need to
change with any regularity is the one for Color Depth, and even
then, the non-default settings are likely to be useful to only
a small cadre of advanced users. Herewith the Preferences functions:
- Auto Expose for Slides - This appears to be an overall
exposure compensation adjustment for scanning very dense transparencies.
It made no perceptible difference with our "train"
slide though, perhaps because that slide also includes some very
light areas.
- Close Driver After Scanning - This will be most useful
when using either a TWAIN or Photoshop acquire module for scanning.
It will close the scanning window after each scan, returning
you to the host application. (Or to the desktop, if you're running
standalone.)
- Prescan Size (Options are Small, Large, or Auto) -
You can preset the size of the prescan window, or allow the scanning
software to size it to your screen automatically. The last is
the easiest, the fixed sizes perhaps being useful if you want
to be able to see other windows on your desktop while the scanning
software is running.
- Color Depth (Options are 8-bit, 16-bit, and 16-bit linear) - As mentioned earlier, the Dimage Scan Speed is a 12-bit per channel scanner. Since computer displays and most programs can only accept 8 bits per channel, what happens to the rest? Normally (in 8-bit mode), the scanner and scanning software translate the 12-bit data down to the 8-bit final data size, in effect "choosing the best 8 bits." For most uses, this is the easiest and most direct thing to do. For difficult subjects with particularly wide dynamic ranges though, you may want to employ some unusual tonal mapping, to preserve both shadow and highlight detail, or experiment with different approaches after the scan is complete. For these situations, Minolta provides the ability to capture all 12 bits per channel, and store them in a file. Since the TIFF file format only recognizes either 8 or 16 bits per channel, the option which preserves the full 12 bits of original data is labeled "16-bit," even though only 12 bits per channel are actually being stored. It's a little harder to understand the need for the "16-bit linear" option, but perhaps it has some use in scientific applications. What it appears to do is to turn off the analog "gamma" adjustment that takes place prior to the digitization of the image data. The same raw data is being captured, but the distribution of bits across the tone curve is very different. (In general, dark areas look VERY dark with the 16-bit linear option enabled.) As we said, this doesn't appear to be terribly useful for general photographic applications, but could find some use in photogrammetry.
APS Settings - not having had the APS attachment to play with, we didn't have an opportunity to experiment with these, and the main manual offered no description. Below are our "best guesses" as to what they do:
- Index Scroll Direction (Options are Horizontal or
Vertical) - APS pre-scans produce arrays of thumbnail images.
This option simply selects whether the display is set to scroll
horizontally or vertically as you move through the array of images.
- Index Scan Priority (Options are Speed or Quality)
- With up to 40 frames on a roll, you may sometimes prefer a
"quick and dirty" pre-scan in order to view all your
images quickly. At other times, you may want a higher-quality
prescan, to facilitate image adjustments prior to the high-resolution
scans themselves. (Note that you don't have to pre-scan the entire
roll, if you know which image you're interested in, based on
your APS index print: The software apparently displays blank
thumbnails as soon as the roll is loaded, allowing you to choose
the image you're interested in, based on frame number.)
- Max # of Frames - We're not sure what this control
is for, unless it's to restrict the pre-scan operation to the
first few frames of a roll
- Auto Film Rewind - Apparently an option to rewind
the film back into the cartridge after the scanning is completed.
- Rotate All Frames 180 degrees - Depending on how the APS cartridge loads into the camera, rolls from some models could come out "upside down." This checkbox avoids the need to laboriously flip every individual frame separately.
Prescan Window
This window (shown below) is "home base" for the scanning
process. From here, you'll launch off into other functions within
the software, to adjust color balance, contrast, or tonal range.
Controls here also adjust preview orientation, data readout,
and exposure parameters for sequential scans. See the text following
the screen shot for a description of the individual buttons and
controls.
Here are the Prescan Window controls, reading from left to right
and top to bottom, for all the buttons down the left-hand side
of the screen:
Orientation and Viewing Controls
- Rotate Left Button - Rotates preview (and final scan) 90
degrees to the left. (Counterclockwise)
- Rotate Right Button - Rotates preview (and final scan) 90
degrees to the right. (Clockwise)
- Flip Horizontal Button - Flips picture horizontally.
- Flip Vertical Button - Flips picture vertically. (The two
"flip" buttons find frequent use when flipping the
slide or film carrier to scan frames at both ends.)
- Full-Screen View Button - Enlarges the currently-selected
region of the pre-scan window to full-screen size. (Note though,
that this enlargement is only a pixel replication, so it becomes
rather pixellated when smaller regions are magnified.)
- Zoom Button - Zooms in on a selected area of the pre-scan
window.
- Auto Exposure Lock Button - The scanner normally performs
an autoexposure adjustment prior to each scan. Sometimes, you'll
want to treat all slides or negatives of a group the same (for
instance if they're going to be used together to make a panorama).
To accommodate this, click the Auto Exposure Lock button after
pre-scanning the first image. This will lock the exposure settings
to those calculated for the first image of the group. (NOTE though,
that this doesn't lock or save any exposure adjustments made
with the Histogram, Variations, or Tone Curves controls.)
- "Grab" Button - This button turns the cursor into a "grabber", that lets you drag the pre-scan image and drag it around, to see various areas when the pre-scan image has been enlarged with the Zoom Button.
Image Adjustment Controls
(Buttons in this group take you to other screens, to adjust the
scan settings.)
- Variations Button - This leads to a screen (described in
more detail below), where you can quickly adjust brightness and
contrast, by the simple process of repeatedly choosing the most
appealing of 8 alternate versions of the image. - An excellent
tool for novices to quickly adjust their images.
- Tone Curves Button - Probably at the opposite end of the
ease/power spectrum from the "variations" control,
the tone curves screen (described in more detail later) provides
the powerful ability to edit the tone curves for both the image
as a whole, as well as the individual red, green, and blue channels.
- Histogram Button - This is our favorite scanning/image adjustment
tool! (Also described in more detail later.) To our mind, histogram-based
image adjustment offers the best tradeoff between ease of use
and power for most mid-level users.
- Reset All Button - This button resets all the image adjustments
to their default settings, letting you quickly back out of a
set of adjustments and return to "zero."
Readouts/Information Displays
At the bottom left-hand corner of the Prescan window, there are
two sets of readouts, one showing the dimensions of the current
cropping frame, in mm, and the other the RGB (or CMY) values
of the point under the cursor in the preview window.
Variations Adjustments
It's often difficult for novices to decide what to do to an image
to make it look better. More contrast? Less brightness? A little
of both? Frequently, after playing with an image for a few minutes,
you end up with something that looks worse than when you started!
Yet, even the rankest amateur can generally tell whether picture
"A" looks better than picture "B". Taking
advantage of this, Minolta offers a "Variations" tool,
as shown in the screen shot below. Here, the current contents
of your cropping frame are displayed in the center of a matrix
of images, with those around the edges of it representing the
effects of more or less contrast or brightness. (Contrast variations
run vertically, brightness variations horizontally.) If you decide
you like one of the variations presented more than the current
image, just click on it: It becomes the new reference sample,
and the variations adjust to reflect changes relative to the
new center image. By continuing to click on the image that you
like best, you can quickly home in on the optimum brightness/contrast
setting.
After you've set the contrast and brightness, you can then
correct the overall color balance of the image, by adjusting
the R, G, and B slider controls at upper left. Always wait to
adjust the color until after you've made the brightness &
contrast changes though, as you'll frequently find that perceived
color problems diminish once the brightness and contrast are
properly set.
The "Variations" screen also has a button that enlarges
the current selection to full-screen size, making it easier to
assess the current picture quality. We felt that this feature
was marred slightly by the fact that the enlarged image is only
a pixel-replicated copy of the original area, which can lead
to rather pixelated images if your cropping frame is small relative
to the overall film area.
Histogram Adjustments
As we noted earlier, Histogram adjustments are by far our preferred
method for quickly correcting tone and color problems in digital
images! For those not familiar with histograms though, a brief
explanation would probably be in order.
A histogram is simply a graph of how many pixels in an image
have each possible brightness value. A large peak on a histogram
graph means there's a lot of pixels (a large area) with roughly
the same brightness values. Likewise, if the histogram curve
is near zero, it means relatively few pixels have those brightness
values. To understand how this helps image adjustment, we've
included a couple of sample images at right, showing two images
set up with different brightness and contrast settings, and the
histograms associated with each.
 Dull, flat image has a compressed histogram, with no information above the midtone level in any channel. |
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In the first sample, we have a rather low-contrast, dark image. Low contrast means that there's not a great deal of difference in the brightness values between the brightest and darkest pixels. "Dark" means that the bulk of the pixels in the image have fairly low brightness values. In the histogram curves for this image, note how the right-hand side of the curves (high brightness values) are flat, because there aren't any pixels with those brightness values. Also, note how the histogram curves occupy a fairly small amount of the horizontal space allotted to them.
 Well-balanced image shows full range of tonal values in histogram, in all channels. |
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By contrast (no pun intended!), observe the image above: Contrast
and brightness are about right, and the results are readily evident
in the histogram curves for it. Notice how the curves occupy
much more of the available horizontal space, meaning that pixel
values are spread much more evenly across the available tonal
range. Notice too, how you can even tell about color balance
from histogram displays. Notice the large "hump" near
the middle of each curve? What object in the image do you suppose
this large group of pixel values corresponds to? (It's the background.)
Now, if we want the background to be a neutral gray, what do
you suppose the display would look like. (The peaks in red, green,
and blue would all line up with each other, meaning that the
average R, G, and B values would be about the same.) Can you
guess how the color balance needs to be adjusted to achieve this?
Notice the sliders under the individual histogram curves. These
are used to set the brightness values the scanner will consider
to be the minimum (black), maximum (white), and a middle value
(gray), for each of the color channels. If you move the "black"
slider up from the leftmost position, you're telling the scanner
to treat that value as "zero" for the color channel
involved. Any values darker than that will also be treated as
zero, and values brighter than it will be proportionately stretched
downward so that the brightness values will extend smoothly down
to zero. Likewise, the "white" slider on the right
sets the value that will be considered as a maximum, and mapped
to a digital value of 255. Anything brighter will also be set
to 255, and darker values will be "stretched" smoothly.
The middle slider sets the value that the scanner will put in
the middle of the brightness scale (the "50%" point).
Anything brighter than the level set by the slider will be made
brighter than 50%, anything darker will be made darker. Thus,
to lighten the image overall, you'd move this slider to the left,
so that more of the brightness values would be pushed above the
50% point. (This all sounds more complicated than it is: You'll
figure out what the sliders do after just a couple of minutes
of playing around.)
The histogram screen includes "before" and "after"
previews, and a number of controls for adjusting the image. At
middle left are three of the most immediately useful tools, the
eyedroppers for setting white, black, and gray points. If you
select the black eyedropper button, and then click on a point
in the left-hand preview window, that point will be set as the
"black" point, and the individual red, green, and blue
black-point sliders will all adjust automatically to make it
so. Likewise, selecting the white eyedropper button and clicking
in the left-hand preview window will set that point as the "white"
point, moving the red, green, and blue white-point sliders as
needed. (Anyone want to guess what the gray eyedropper button
does?) In practice, you'll find that the eyedropper controls
offer a very quick way to color-balance many problem images in
a matter of seconds.
Part of the beauty of the Dimage Scan's histogram screen is
the way it shows histograms for all three color channels separately,
yet also allows you to operate on all the channels at the same
time, if you wish. By default, you can adjust any of the slider
controls independently of any other. What if you want to make
an overall adjustment to the image as a whole, though? In the
lower left-hand corner, the button with the three colored bands
on it is the "RGB synchro button." Clicking this button
locks the sliders for the red, green, and blue histograms together,
so that moving any one of them moves the sliders for the other
two colors the same amount.
The other control buttons in the lower left-hand corner let you
see the effects of your adjustments on the histogram, as well
as save and retrieve complete sets of adjustments once created.
This last ability is a particularly welcome one, as many lower-end
scanners don't permit you to save adjustments for later use.
Often, we find ourselves wanting to save a group of settings
before engaging in further experimentation, so we have a known
good point to return to if our twiddling goes awry. Also, you
may have a group of photos shot under similar conditions that
would all benefit from the same treatment.
One odd point about saved and subsequently recalled histogram
corrections though: When the DSS Scan software applies a previously
saved correction to an image, it does so on top of whatever
correction may currently be in effect. Thus, the effects of recalled
corrections are cumulative with any you've already applied.
If you want to return to a prior state, you'll need to reset
all corrections (using the Reset button) before applying the
saved settings. (This isn't any sort of a problem, but was different
than how we expected the saved settings to work. We're passing
the information along here to hopefully save our readers a few
minutes of puzzlement when they encounter the behavior for the
first time.)
A full treatment of histogram-based tonal adjustments is far
beyond the scope of this review, but we encourage users to spend
some time playing with the controls on this screen: They're simple
to master, but quite powerful to use.
Tone Curve Adjustments
The tone curves window (shown below) offers a set of controls
that are at once easier to understand than those of the histogram
display, yet considerably less straightforward to apply effectively.
Even here though, minor tweaks by Minolta contribute greatly
to ease-of-use.
In concept, tone curve controls are as simple as can be: They're
nothing more than a graph of output brightness values against
input brightness values. Essentially, they say "whenever
you see brightness 'x', replace it with brightness 'y'. The input
brightness values (those of your original image) are arranged
along the horizontal axis of the graph, and the output values
(those your image will come to assume) are arranged along the
vertical axis. Again, the easiest way to understand how a tone
curve works is to play with one. A little experimenting will
reveal that a steeply sloping curve produces high contrast, while
a flatter one produces less. Likewise, a curve bulging upward
results in a brighter image overall, and one drooping downward
makes for a darker one. The Dimage Scan software lets you adjust
either the overall RGB curve, or each of the color channels (red,
green, and blue) individually.
Tone curve controls let you adjust parts of the tonal scale,
without affecting others. As such, they're more powerful than
the histogram controls, but you have less feedback as to what
parts of the image you're affecting, and it's much easier to
get lost in your adjustments with them. Experienced graphics
professionals rely on tone-curve adjustments almost exclusively
though, because they provide such a high degree of control over
the tone and color balance of images.
The tone curve controls in the Dimage Scan software work like
those of most any high-end image editing program: You can click
any point on the curve and drag it, and the rest of the curve
will bend smoothly to pass through the point you've defined.
You can set multiple control points by clicking on more than
one part of the curve. You also have the ability to draw your
own curve, using a pencil tool, allowing you to create abrupt
discontinuities if desired. Minolta added a unique twist to the
tone curves though, in the form of white and black-point eyedropper
controls, which work in the same way as the equivalent controls
on the histogram screen. While a seemingly minor point, the eyedroppers
can quickly make gross adjustments in the overall tone and color
balance, and provide a good jumping-off point for your own finer
adjustments.
Test Results
As always with Imaging Resource reviews, we encourage you to
let your own eyes be the final judge: Look at the sample
images, download them, print them out on your own printer,
and decide for yourself how well the Dimage Scan Speed would
meet your requirements!
Overall, the Dimage Scan Speed turned in a very competent performance,
easily besting the current crop of "consumer" film
scanners in most areas. (As you'd expect from a scanner selling
for $1,299, vs as little as $300 for the low-end devices.) Particularly
when compared to the digital cameras that constitute the other
major review focus of this site, readers are bound to be impressed
with the incredible amounts of detail a scanner like the Dimage
Scan Speed can extract from a slide or negative.
We found that the Dimage Scan Speed produced very good scans
with the default settings, and excellent ones with only minor
tweaking of the scan controls. On the PC, the default settings
tended to produce slide scans that were slightly dark, but a
minor bump of the midtone point using the histogram control would
quickly bring the overall tone into a reasonable range. By comparison,
scans of color negatives were a bit light, but a minor drop of
the midtone point tended to quickly compensate. Color balance
overall was quite good, although by default, the scanner tended
to add a bit of magenta to things (red and blue together). We
suspect this might be an attempt to compensate for typical computer
monitors, which tend to have a very bluish white-point, frequently
as high as 9300K. Again, it wasn't too difficult to compensate
for this tendency, and the ability to save and recall sets of
tone and color corrections was a valuable feature. Overall color
accuracy was excellent, with color saturation just a notch away
from the very best we've seen to date (January, 1999). We did
notice a tendency on the transparency (slide) shots to undersaturate
greens somewhat, though...
Resolution of the Dimage Scan Speed was excellent, but hard to
"call" based on our standard test targets. The reason
for this is that an unusually low level of "aliasing"
had us convinced we could easily see discernible detail in the
WG-18 target all the way out to 1800 line pairs per picture height
in both horizontal and vertical directions. This doesn't make
sense, given that there are only 2600 pixels vertically in the
resolution-target image, meaning we really "shouldn't"
be able to see anything beyond about 1300 line pairs/picture
height. Nonetheless, the scanner clearly resolves the target
out to 1400 lp/ph, and a good bit beyond. (Note that the slight
cropping the scanner did to the 35mm frame wouldn't be nearly
enough to produce the increase in apparent resolution we observed.)
The USAF resolution target gave (as usual) more conservative
resolution figures, with the scanner resolving cleanly down to
35.9 line pairs/mm, (912 line pairs/inch), and with some aliasing,
down to 45.8 lp/mm (1163 line pairs/inch). With natural subjects,
the scanner's fluorescent light source produced a somewhat softer,
less grainy look than some other units we've tested, although
there seemed to be no loss of detail information in the scans
associated with this softer "look".
See for Yourself!
Take a look at the test images from the Dimage Scan Speed, download
them, print them out, and see if this scanner meets your needs!
Conclusion
In the Dimage Scan Speed, Minolta has crafted a combination of
capabilities and software features into a unit that produces
good image quality with a minimum of tweaking. Even better, when
it does come time to manipulate color and tone, the software
controls provide a full range of capabilities, satisfying users
ranging from rank amateur to experienced color professional.
For More Info
Visit the Minolta
web page for the Dimage Scan SpeedView the Minolta
"How2Scan" On-Line Demo Web Site
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