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Pentax 645D Overview

by Michael R. Tomkins, Zig Weidelich, and Shawn Barnett
December 3, 2010; Updated October 18, 2011

Pentax aroused quite some interest when it first announced that it was working on the design of a medium format digital SLR, dubbed the Pentax 645D, way back in March 2005. Harkening back to 1984's Pentax 645 film camera, the 645D would feature a high-resolution Kodak CCD image sensor, a 645 AF mount, and compatibility with existing Pentax 645 interchangeable lenses. The development process was lengthy, and the specifications were subsequently updated to keep pace with a rapidly developing digital camera market, before the company's merger with optics giant Hoya Corp. led to the project being placed on indefinite hold. In March 2010, Pentax revealed that it had continued development of the camera, which was now nearing launch after another overhaul had placed a 40-megapixel Kodak KAF-40000 image sensor at its heart.

Available in Japan since May 2010, the medium format Pentax 645D digital SLR attracted strong demand in that market from 645 owners who'd patiently waited through the development process, and were finally rewarded with the combination of mighty resolution and a weather-sealed medium format body. Photographers in other global markets have had to wait a little longer, as Japanese-market demand kept the production line busy, but this delay provided Pentax with time in which to prepare an after-sales service strategy for the camera. In October 2010, Pentax USA announced that the 645D would ship in the US market by the end of the year, priced at around US$10,000, and that this price tag would include automatic enrollment in Pentax's Professional Services Program, which offers access to a dedicated team of 645D specialists on weekdays (excepting holidays), from 7:30am to 4:30pm Mountain Time. The wait for US-market Pentaxians was finally at an end.

Look and feel. Though the Pentax 645D is a very large camera, it's not quite as heavy as you'd expect, and it's surprisingly comfortable to hold and use. Body-only the 645D weighs 2.15 pounds (34.5 ounces; 977g). It's hefty, but the weight is well distributed, and the grip is just right for comfortable carry. Now, I don't recommend you take it to an amusement park for snapshots, nor wear it around your neck for a casual stroll. Its $10,000 price tag warrants that you treat it more like a Katana sword, leaving the Pentax 645D in its case until you're ready to use it.

Looking at the Pentax 645D from the upper right, you can see it's no ordinary SLR. Buttons are aligned on the left of the prism housing, and there's a vertical tripod mount on the left of the camera. You don't want to be hanging this two-pound camera sideways on a ball head, to be sure, and you also don't want to have to buy an L-bracket, so Pentax built it right in.

From the front, you see the gaping hole created by the large lens mount on the 645D. The large tapered grip includes an infrared remote port, the front dial, and the same set of controls as you'll find on a Pentax SLR, including the Power switch surrounding the shutter release backed up by the EV and ISO buttons. Mounted on the upper left of the lens housing is the Mirror Lockup dial. Moving the dial doesn't lock up the mirror as it once did on old mechanical cameras, but when you press the shutter release the mirror locks up and the camera beeps waiting for you to press the shutter release again. It's a really big mirror, so it's good they gave the control its own physical switch. Lower left of the lens mount is the lens release button, again following other bayonet-mount Pentax cameras. Just inside the mount on the lower right you can see the screw-drive coupling for the autofocus motor. With our review camera, we received one older screw-drive lens and one SDM lens, which I mention so that you know the 645D is state of the art.

From the top it quickly becomes clear that this is a photographer's camera, replete with dials and buttons. The four buttons on the left have some interesting functions, including adding a RAW shot to the next image, setting what kind of file you're recording on each of the 645D's two SD cards, and selecting a bracketing mode (you hold down the button and use the front dial to choose the mode, with the rear dial adjusting the magnitude).

You can make most of these adjustments via the top Status display or the rear LCD. The Status display is angled backward sufficiently that I preferred it most of the time for such adjustments.

The large mode dial locks with a button in the middle. The metering mode dial is on the same axis, with only part of a ring jutting out on the left side of the camera. It seems difficult to adjust at first, but using the side of my left thumb makes it very easy. Surrounding the optical viewfinder is a large knurled ring for adjusting the diopter. It moves in huge steps that nevertheless make very fine adjustments, ranging from -3.5 to +2.0 in 35 steps! There is no center indicator, so you just have to look through the viewfinder and make your image clear.

Left and right of the viewfinder are dials for the focus mode and AF point mode. The latter dial is particularly important for a camera like this, as quickly moving this dial is better than looking to a display to switch between selective points and center point. Admittedly, though, the AF points are clustered so tightly in the center of the frame that there's little difference from one setting to another.

The back view shows just how aggressively canted is the Status LCD. Among the more obvious buttons are buttons like the Custom image button second from left below the Rear LCD. In Playback mode, you can also switch easily between the two SD cards with the press of a button. A remote release port is covered by a rubber flap just beneath that, and the rear infrared remote control sensor is just to the right. Note that the AF button is probably better positioned than on most SLRs, and the AE-L button is just a quick motion away in the other direction.

Dirt to Art. Had my boys pause for a portrait while playing in the dirt. It can't been seen in this thumbnail, but they fairly pop from the background and foreground with an almost 3D effect. Shadow detail is easy to rescue and you can even see the hair on their arms and legs.

Shooting. Though it's big, holding the Pentax 645D is really easy. Something about its shape and balance makes its weight easier to take, and it even feels natural to one-hand for a short time. That's great for photographers who also work off-tripod. We were particularly impressed with the 645D's finger-relief just inside the grip. I gave the camera to Dave to try, whose longer fingers typically bottom out on most SLRs, but the finger cutout is so deep his tips didn't even touch. Yet neither Rob nor I had any trouble with the rather substantial grip. Pentax seems to have struck the perfect balance for most hand sizes. Cradling the camera in the left hand is also comfortable thanks to the large underbelly and chamfered left edge. Weight is evenly distributed, and though the bulk of the body surrounds the mirror box, it's a largely hollow space, which helps offset the weight of the lens.

Counting game. Though it's in shadow, the front of this building is so detailed you can count the bricks with verifiable ease.

It was a nice diversion walking around town with the 645D capturing gallery shots, just as I do with considerably smaller cameras. I just love hearing that massive mirror flipping up and down with each shot. It's comical at first, but reassuring as you go along, because you know you've done something more than just make a snapshot. You've made an incredibly detailed photograph. The pressure is to make it worthy of the camera, and that's a good pressure to have.

The interface is very similar to other Pentax offerings, and the controls are all a photographer could want, with so much available via a dial or button, it's as if the camera wants to work as much as you do.

Bokeh. Again, difficult to see in this shot at this size, the 645D can make large objects seem small. (Click to enlarge to 800px; click again for full size, but get ready!)

By far the greatest pleasure is bringing that unusual round viewfinder up to your eye. It's a nice big, bright image, and you can easily see the Status display below the image without having to press your eye in too tight (my glasses do touch, but I don't have to press them into my eye socket, as I usually must).

Half-pressing the shutter button focuses like any other AF camera, and squeezing it the rest of the way releases the camera's necessarily slow mirror and shutter mechanisms. The sound is what you'd expect a giant's camera to sound like: slower, more deliberate. Depending on card speed, saving to the dual cards can take some time, but I didn't even notice because I wasn't shooting rapid fire. Naturally, you'll want the fastest card and reader you can find to copy the RAW files to a computer, since their size ranges from 50 to 70MB each.

When working on a tripod you have a little more time to consider your options, and they're all clearly laid out before you. One of the more modern options on the 645D is the Digital Level function, allowing you to ensure that the camera is level even when the horizon isn't visible.

Archival. Keeping track of the details is a lot easier with so much resolution, great for archivists.

We did a nearly full test suite on the Pentax 645D, including timing. It starts up quickly, about 0.7 second, and shuts down a little faster. The buffer fills after 19 large fine JPEGs, taking 27 seconds to clear with a SanDisk Extreme III SDHC card. 16 large RAW files take 53 seconds to clear, and 15 large RAW + JPEG images take 71 seconds to clear. Those are fairly long times, but thankfully you can continue to adjust the camera while the buffers are clearing, which is not true of some cameras.

Shutter lag is very good, with the Pentax 645D in single-area autofocus mode able to focus and capture an image in 0.164 second. Auto-area AF mode raises the time to a still impressive 0.180 second. Prefocusing reduces the time to 0.142 second. In single-shot drive mode, the Pentax 645D captures a shot every 1.1 second. Switch to Continuous mode and you can get a Full JPEG or RAW+JPEG shot every 0.9 second, for a 1.1 frame per second capture rate. That's not fast, but remember that big mirror and huge sensor and it's not bad at all.

The transfer speed also moves along at quite a clip. 11,194 KBytes per second to be exact, which is handy considering the massive file sizes. Battery life, for its part, doesn't drain too fast, capable of capturing up to 800 shots per charge; that, of course, does not include flash as CIPA tests usually do, because the 645D doesn't include one.

High ISO performance is also quite good from the 645D, which is not too surprising given its 6 micron pixel pitch. Print size is phenomenal, with ISO 100 through 800 images making excellent 48x36-inch (4x3-foot) prints, and ISO 1,600 shots making crisp 36x26-inch prints, which only have a little luminance noise in the shadows. Quite astonishing what 40 megapixels can do, especially on such a large sensor.

ISO 100 ISO 200
ISO 400 ISO 800
The Pentax 645D maintains very impressive image quality as ISO rises, and though noise does increase, we were still able to produce large prints from its images.
ISO 1,600

Obviously, the Pentax 645D isn't made for everyday photography, and is only for a select few who are very serious about their photography. It certainly is a wonderful tool for documenting just about anything that will stand still long enough to be captured with it, and you'll get tons of detail.

 

Pentax 645D Technical info

Sensor. Based around a Kodak KAF-40000 CCD image sensor, the flagship Pentax 645D offers 40 megapixel resolution, and a 4:3 aspect ratio. As compared to a 35mm full-frame image sensor with 3:2 aspect ratio, the 645D's sensor provides 1.68 times more surface area. Seeking maximum image detail, Pentax has forgone an optical low-pass filter overlying the sensor, a decision that removes the subtle blurring used to prevent moire in most cameras, but means that the 645D must instead combat such image defects using software techniques and lens design.

The Pentax 645D includes many features previously seen in the company's APS-C prosumer K-7 model, as well as the Pentax K-5. These include a fully sealed body that resists dust, weather and cold to -10° Celsius, a PENTAX Real Image Engine II (PRIME II) image processor, Dust Removal II (DR II) mechanism using piezoelectric vibration of the UV/IR cut filter, 3.0" LCD display with 921,000 dot resolution (using a glass cover plate like the Pentax K-7 Limited Silver), power from a D-LI90 lithium-ion rechargeable battery pack, and a selection of USB, HDMI Type-C and NTSC / PAL composite video connectors.

Other features previously seen in the K-7 include copyright tagging, in-camera HDR, dynamic range expansion and distortion / aberration correction, as well as the Color Temperature Enhancement white balance mode that helps emphasis color of sunsets, etc. Like the K-5, there's also a dual-axis digital level function (but without automatic level correction, since the sensor isn't mounted on a movable platter).

Like the K-7 and K-5, the Pentax 645D meters exposures with a 77-segment sensor offering three modes -- multi-segment, center-weighted or spot. There's also an 11-point phase detection AF system with continuous and single operation, and the ability to select points automatically or manually, and the AF sensor chip carries the same SAFOX IX+ designation as in the K-5.

Like the company's APS-C flagship models, the 645D's images are stored on SD or SDHC cards (firmware 1.01 adds support for SDXC cards), but the Pentax 645D differs from its more compact siblings in offering two SD card slots to allow either automatic overflow, simultaneous backup or segregation of images by file type.

Eight creative modes like those in the K-7 and K-5 allow tuning of parameters like contrast, saturation, hue, sharpness, and more. The 645D's on-screen interface also looks to bear more than a passing resemblance to that of the K-7 and K-5, although with some rearrangement to cater to pro use and the camera's differing feature set.

Many points where the Pentax 645D varies significantly from its prosumer siblings - beyond the medium format lens mount and sensor, and the pro-friendly body with features such as a mirror lock-up knob - is in its variables relating to exposure. Burst shooting is possible at 1.1 frames per second for 15 JPEG or 13 RAW frames. (We managed a few more frames in our testing.) Shutter speed ranges from 1/4,000 to 30 seconds plus bulb (with noise reduction after 30 seconds), where the APS-C models have a maximum 1/8,000 second shutter speed.

Shutter life is rated at 50,000 cycles, half that of the K-7 and K-5. Sensitivity ranges from ISO 200 to 1,000 equivalents ordinarily, and can be expanded to a range of ISO 100 to 1,600. As you'd expect given the target market (and the much greater sensor size and weight), there's also no in-body image stabilization. There's likewise no live view or movie functionality, due to the choice of a CCD image sensor rather than a CMOS chip, with images being framed on a trapezoid prism viewfinder offering 98% field of view.

Only one notable function really appears may be absent for the Pentax 645D's target market: like all of Pentax's recent models, the 645D lacks any provision for tethered shooting. As we've noted in past reviews and news coverage, this is something we'd hope to see the company rectify in the future. Tethering can add significant convenience in studio shooting, as an alternative to "sneakernet" transportation of flash cards between camera and computer. With a greater selection of third-party software such as Adobe's Photoshop Lightroom beginning to offer provision for tethered shooting from other brands, awareness of the feature -- and of its absence in Pentax's cameras -- will likely continue to grow.

 

Pentax 645D Comparison Photos

Pentax 645D versus Nikon D3X

The Pentax 645D seems smaller than the Nikon D3X; that is, until you see it from the top, where its thickness is most apparent. Body-only, the Pentax 645D is also heavier than the D3X at 52.2 ounces (1,480g) versus 43 ounces (1,220g). Both are pro cameras, priced within a few thousand dollars of each other.


Pentax 645D versus Pentax Q

Since we have them both in-house, we thought we'd compare one of the largest SLRs to one of the smallest compact system cameras, the Pentax Q. At 12 megapixels and 8.3 ounces, the Pentax Q is considerably smaller in many ways, yet still offers a 3-inch LCD and a full-size hot shoe. It also sports a unique pop-up flash, which the 645D does not.

 

Pentax 645D Image Quality

As you'd expect from its 40-megapixel resolution and medium format sensor size (actually, 44 x 33mm; somewhat smaller than the 56 x 41.5mm 645 film frame), the Pentax 645D captures phenomenal amounts image of detail. Below are some JPEG crops at default settings comparing the Pentax 645D to the current 35mm, full-frame resolution champs, the 21.1-megapixel Canon EOS-1Ds Mark III and the 24.5-megapixel Nikon D3X. We don't post these, by the way, to tout one camera over another, but rather to show what 40 megapixels and the physically larger sensor can do. It's also interesting to see just how high quality the Pentax glass appears to be (the 75mm f/2.8 medium-format lens), because as resolutions increase, optical quality becomes even more important.

Pentax 645D versus Canon EOS-1Ds Mark III at base ISO

Pentax 645D at ISO 200

Canon 1Ds Mark III at ISO 100

We're going to have to start reusing superlatives at some point here, so bear with us.

At their base ISOs, both cameras turn out impressive results, but both also have trouble in the red channel--the Canon considerably more so than the Pentax.

We've never seen so much detail from any camera we've tested, of course, including on the olive oil bottle, which appears to have much more texture than other cameras can reveal. Indeed, we had to go down to the lab and inspect the Still Life test target again to verify the incredible detail that the Pentax 645D finds from several feet away with the 75mm lens.

The mosaic bottle label is from an offset press with a fairly fine halftone pattern that we've never noticed before. As such, the purples, blues, yellows and greens that appear between the black tiles in the 645D's image are really there, as are the slight color patterns in the character's cloak.

For the first time, all of the fabric swatches show clearly visible threads, whereas only a few do on the 1Ds Mark III and D3X. At its base ISO of 200, the 40-megapixel Pentax 645D does better with our most troublesome red leaf fabric swatch than any camera to date. Clearly the Pentax 645D outresolves the 21.1-megapixel Canon 1Ds Mark III at ISO 100, but that's really no surprise given the 2x higher megapixel count. We weren't expecting to see so much more detail, though.


Pentax 645D versus Nikon D3X at base ISO

Pentax 645D at ISO 200

Nikon D3X at ISO 100

Naturally the 24.5-megapixel Nikon D3X turns in a better performance than the 21.1-megapixel Canon 1Ds Mark III, but it's also clearly bested by the Pentax 645D. It's interesting to note that the Nikon D3X actually seems to remove the colors between the mosaic tiles that are actually present in the subject. This creates a bit crisper-looking image, if one that's less true to the almost microscopic detail captured by the Pentax 645D.

And while the D3X makes a crisper rendering of the red leaf swatch that beats that of the 1Ds, the Pentax 645D reveals the very threads that cause other cameras so much trouble as noise suppression systems struggle to separate the dark reddish lines from the underlying fabric texture.


Pentax 645D versus Canon EOS-1Ds Mark III at ISO 1,600

Pentax 645D at ISO 1,600

Canon 1Ds Mark III at ISO 1,600

At ISO 1,600, the Pentax 645D still manages to output more detail than the 1Ds Mark III, including the slight color noise between the black mosaic tiles. While it starts to have trouble resolving the thread pattern of the red leaf swatch, it's still able to see the pattern in the pink cloth below it. Very impressive.


Pentax 645D versus Nikon D3X at ISO 1,600

Pentax 645D at ISO 1,600

Nikon D3X at ISO 1,600

Up against the D3X at 1,600, the Pentax 645D still holds onto crisper, truer detail, as one might expect. (The 645D's pixels are actually almost the same size as those of the D3x, but there are more of them to cover a given subject area, so the camera has more to work with, in separating image noise from subject texture.)


As you can see, the Pentax 645D is capturing details in our Still Life shots never seen before on screen. Check the Samples page for full resolution images. As always, we encourage readers to download and view our camera-direct files for their personal use -- but you might want to consider making a donation toward bandwidth costs using the buttons on the image-carrier pages; these are huge files! (The JPEGs run 15-20MB each; the DNGs are 50-70MB.)


Pentax 645D Print Quality

ISO 100 shots make excellent 36x48 inches; ISO 400 shots are sharp at 30x40 inches; and ISO 1,600 shots make great 16x20-inch prints.

We had to establish new maximum print sizes for the Pentax 645D, as it's the first 40-megapixel camera we've reviewed. Something tells us it won't be the last, but for now the maximum tested print size is 40x60 inches.

ISO 100 images are what we'd call usable at 40x60 inches, certainly for wall display with some sharpening applied. Straight out of the camera, though, they look better printed at 36x48 inches. That's 3x4 feet. Detail is excellent at this size, as is color.

ISO 200 shots are also quite good printed at 36x48. Very sharp, excellent detail.

ISO 400 images are slightly soft at 36x48, but return to crispness at 30x40.

ISO 800 images print beautifully at 30x40.

ISO 1,600 shots take the first (and last) noticeable hit in quality, requiring more noise suppression. While they're usable at 30x40 and quite a bit better at 20x30, they don't quite measure up to the standard of the others until 16x20, still a gigantic print.

Overall the Pentax 645D turns in a stellar performance worthy of a medium-format camera. Image quality is amazingly good, and we were quite conservative of our judgments on print quality. Lowering noise suppression or processing RAW images would likely achieve even larger print sizes with ease.

 

(Minor) Sensor Issue

Pentax 645D, ISO 200 default NR

Pentax 645D, ISO 200, no NR

Sometimes, our test targets show minor sensor defects that are virtually invisible in real-world images. For example, the sharp black/white contrast of the resolution chart often shows artifacts from the pixel-substitution used to fill in for faulty sensor pixels. In the case of the 645D, an artifact of this sort appears in our Viewfinder Accuracy test target images, at pixel column 2799. The crop above left shows the effect, a slight blurring of the edges in the red rosette pattern.

We call this a "minor" sensor defect, because the results are actually incredibly hard to see in images of real-world subjects: If we didn't know what we were looking for and exactly where to look for it, we'd almost certainly never notice it. To demonstrate this, check out the crop from our Still Life target above right, shot with noise reduction turned off to minimize the chance that the NR processing would hide the issue. Can you see the artifacts? We didn't think so. (If you look really closely, you might be able to make out the errant pixel or two in the black drop-shadow under the gold trim, and again in the drop-shadow from the vertical stroke of the "F".)

We call attention to this mainly to save on bandwidth: Someone would be bound to notice the issue on the VFA chart eventually and note it on an internet forum, after which thousands of other people would hit our server, downloading multiple 20-MB files to see whether they could see it or not. Hopefully the above examples will save all of you the time and our servers the bandwidth. Bottom line, this is pretty much of a non-issue, unless your business is photographing test charts.

 

Conclusion (for now)

Given that the Pentax 645D is out of the realm of cameras we normally test, we went back and forth on whether to do a full image analysis, but we've decided to go forward. Look for that soon. We wanted to flesh out what we posted late last year with a little more experiential writeup and final thoughts before sending the 40-megapixel 645D back to Pentax. It's really an amazing camera, with plenty of pixels to spare, and very high-quality optics.

Aside from all that "gee-wiz look at all the pixels," it's clear that for anyone doing high-end portrait, graphic reproduction, landscape and architectural photography should be giving the relatively affordable Pentax 645D a look, as it's priced just a little higher than a Nikon D3X, and considerably lower than the Hasselblad H4D-40.

We especially appreciated its easy demeanor and ready controls that made us even more comfortable making adjustments than we are with 35mm and APS-C SLRs. Having all that extra body real estate allowed Pentax to give us the extra control we like to have. We feel pretty safe strongly recommending the Pentax 645D to anyone in need of a medium format camera.

 

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