Sony A700 Image Quality
Sony A700 Imaging Characteristics
Image and file quality are the ultimate bottom line for digital cameras, and the Sony A700 generally does well in this area, but we were surprised to see how much more image detail is contained in its RAW files than ever make it out through the in-camera JPEG processing. It's a camera with very different personalities, detail-wise, depending on whether you're looking at in-camera JPEGs or the results of careful RAW processing. See the sections below to understand what we mean by this.
Resolution and Detail
High resolution, ~1,650 lines of strong detail from in-camera jpegs, 1,750-1,900 lines from raw.
Our laboratory resolution chart revealed sharp, distinct line patterns down to about 1,650 lines per picture height horizontally and vertically from in-camera JPEGs, but we got much better results using Adobe Camera Raw to process the raw file - about 1,900 lines horizontal, 1,750 vertical. The third set of crops above show the results from a 2x resolution target (all numbers must be multiplied by 2), which basically shows the same results, before aliasing becomes so strong as to swamp the target patterns. Use these numbers to compare with other cameras of similar resolution, or use them to see just what higher resolution can mean in terms of potential detail.
Sharpness & Detail
Two very different personalities: Very noticeable detail loss in in-camera JPEGs, incredible detail in properly-processed RAW images.
Sharpness. The Sony Alpha A700 captures reasonably sharp images, with good detail. Some minor edge enhancement artifacts are visible on high-contrast subjects such as the crop above left, but results are still quite good. Edge enhancement creates the illusion of sharpness by enhancing colors and tones right at the edge of a rapid transition in color or tone.
Detail. This is an area where the Sony A700 either suffers somewhat or does incredibly well, depending on the image file format you use. In-camera JPEGs (even in Extra-Fine mode) lose significant detail, particularly in areas of subtle contrast. It's a guess, but our thought is that this is likely due to over-aggressive noise suppression processing, even at low ISO settings. The standard crops above show this somewhat in Marti's hair, more so in the lack of texture and detail in the pine needles of the crop from the far-field image on the left. We'll take a look at the differences between RAW and JPEG files in the next section below. Noise-suppression systems in digital cameras tend to flatten-out detail in areas of subtle contrast. The effects can often be seen in shots of human hair, where the individual strands are lost and an almost "watercolor" look appears.
RAW vs In-Camera JPEGs
As noted above, the Sony A700 has two distinct personalities when it comes to image quality. It's a completely different camera, depending on whether you look at its in-camera JPEGs or RAW files. Take a look below, to see what we mean:
In the table above, mousing over a link at the bottom will load the corresponding crop in the area above. Examples include in-camera Fine JPEG, in-camera Extra-Fine JPEG, RAW file processed through Sony's Image Data Converter SR version 2 software, and RAW file processed through Adobe Camera Raw version 4.2, then sharpened in Photoshop. (I've found that sharpening results in ACR are inferior to those obtained with the Unsharp Masking tool in Photoshop itself. For the Sony A700's images, I found best results with no sharpening at all in ACR and then 250% unsharp masking with an 0.3 pixel radius.)
Apologies for the slight exposure difference above, between the Fine and Extra Fine examples, one was shot with the default settings, the other in Extra Fine mode but with the contrast explicitly set to the middle value, which apparently changed the exposure slightly. We'll try to reshoot when we're back out with the A700, when we get the second kit lens. ACR also renders colors somewhat differently than either the A700 or the Sony software, so the greens in the trees are rather different. There's no mistaking the increase in detail though, regardless of changes in color or tone.
The images themselves tell the story: Even in its Extra-Fine JPEGs, the Sony A700 loses considerable image detail. (As some readers have pointed out to me, fairness demands mentioning that it's not alone in this; Many current cameras give up a lot of subtle detail in forming their JPEGs. I'll be evaluating this going forward, will hopefully be sharing some comparisons with our readers at some point in the future.)
In the case of the Sony A700, careful processing of its RAW files delivers really exceptional detail and tonal nuance. It's very, very worthwhile spending the time to process the A700's RAW images, rather than working with its JPEGs. You'll certainly still get acceptable snapshot-quality images from the JPEGs, but the RAW image quality is really of an entirely different level.
Here's another look, at samples from the "Sunlit" Portrait shot:
|Extra-Fine JPEG from the camera, 16-80mm f/3.5-4.5 Carl Zeiss lens, shot at f/7.1. You can pick out some hairs where they contrast strongly with their background, but there's a lot of soft mush, probably from noise-reduction processing.||Image from RAW, through Adobe Camera Raw v4.2, shot a few minutes later with the same settings as the image at left. Exceptional fine detail, and relatively low noise. (Luminance noise reduction was set to 20, chroma noise reduction to 30 in ACR. Unsharp masking of 250% at 0.3 pixel radius was applied in Photoshop after the image was imported.|
These images aren't from the same shot, as the Sony A700 only saves fine-mode images when shooting RAW + JPEG. The lighting and focus should be identical though, as I was using manual focus at this point, and you can see that even minor details of Marti's hair are the same between the two images. I was also shooting with a fairly small aperture (f/7.1) to give me good depth of field. Bottom line, it's not 100% guaranteed that the two images have precisely the same focus, but I don't think the in-camera JPEG image is at all out of focus. Once again, the improvement with the RAW file is little short of amazing.
Saturation & Hue Accuracy
Very good color overall, though a tendency toward darker blues. Generally good saturation and hue accuracy.
Skin tones. Here, the A700 did very well, producing natural-looking skin tones that were neither over- nor under-saturated, with very natural hues. Where oversaturation is most problematic is on Caucasian skin tones, as it's very easy for these "memory colors" to be seen as too bright, too pink, too yellow, etc.
Hue. The A700 did introduce several small hue shifts, moving cyan towards blue slightly, and purples back toward blue slightly as well. Reds went very slightly to orange, but the overall hue accuracy was quite good, with an average delta-C (formerly known as delta-E*ab) of only 4.81 after correction for luminance and saturation. The other important part of color rendition is hue accuracy. Hue is "what color" the color is.
As mentioned above, the Sony A700 has a saturation adjustment, available via the Creative Style submenu off the first Record-mode menu. A total of 7 settings are available, three above and three below the default saturation. This covers a pretty wide range of saturation levels, about as wide a range as you're likely to find photographically relevant, apart from special effects that are arguably better achieved in software. The fine steps between settings mean you can program the camera to just the level of saturation you prefer.
|Saturation Adjustment Examples|
The table above shows results with several saturation settings, see the Thumbnails index page for more (look for the files named A700OUTSAT0x.JPG). Click on any thumbnail above to see the full-sized image.
Exposure and White Balance
Indoors, incandescent lighting
Warm cast with Auto white balance setting, but good results from the Incandescent, 2,800 Kelvin, and Manual settings. About average positive exposure compensation required.
|Auto WB +1.0 EV||Incandescent WB +1.0 EV|
|Manual WB +1.0 EV||2,800 Kelvin WB +1.0 EV|
The Sony A700's Auto white balance setting resulted in a very strong warm color cast indoors under household incandescent lighting. The Incandescent setting cleaned things up quite a bit, but left a slight warm cast as well. (Many people would prefer this to an entirely neutral rendering, feeling that the slight tinge more faithfully conveys the mood of the original scene.) The Manual white balance produced the most pleasing overall color, while the 2,800 Kelvin setting produced a slightly warm result. The camera required a +1.0 EV exposure compensation boost for a bright exposure (about average for this shot) with all white balance settings. Overall color looks good, though a little dark, the blue flowers in particular looking dark and purplish. (Many digital cameras reproduce these flowers with a dark, purplish tint, so the A700's performance here wasn't at all unusual.) Our test lighting for this shot is a mixture of 60 and 100 watt household incandescent bulbs, a pretty yellow light source, but a very common one in typical home settings here in the U.S.
Good color and exposure, though slightly high default contrast. Lots of options for dealing with high-contrast subjects & lighting though.
|Default Contrast, normal D-R setting|
|4900K White Balance,
|Auto White Balance,
Outdoors, the Sony Alpha A700 performed pretty well, with just a very slight overexposure in the outdoor far-field house shot. The Sony A700 required less than the average amount of positive exposure compensation on the "Sunlit" portrait. Default contrast is on the high side, but fortunately, there's an effective contrast adjustment to help compensate. Even at its default contrast setting, it does an excellent job of holding onto highlight detail: Even though the shirt looks blown out in the thumbnail above, there's actually full detail in it. - More on this below, in the "Extremes" section.
ISO & Noise Performance
Low to moderate noise below ISO 1,600, but high levels at 3,200 and 6,400 equivalents.
|Results from in-camera JPEGs|
|ISO 100||ISO 200||ISO 400|
|ISO 800||ISO 1,600||ISO 3,200|
In its in-camera JPEGs, the Sony A700 produced very low noise levels at low ISO settings, but as noted above, at the cost of considerable loss of fine detail in areas of subtle contrast (where anti-noise processing takes its toll). Images stayed pretty clean as high as ISO 800, but with a progressive and noticeable loss of subtle detail as the ISO increased.. At ISO 1,600, we start to see some blotchiness in the shadows, but detail is still quite good. At ISO 3,200 the grain pattern and chroma noise become quite prominent in the darker areas, and at ISO 6,400, chroma noise and the effects of heavy noise reduction obliterate much of the finer details.
|Results from RAW via Adobe Camera Raw v4.2|
|ISO 100||ISO 200||ISO 400|
|ISO 800||ISO 1,600||ISO 3,200|
|ISO 6,400||ISO 6,400 - No NR||ISO 6,400
Sony IDC, No NR
(A quick note about this second set of crops: They're darker because they're taken from a little lower down on Marti's head than the first set above. The reason for this is that the ISO 100 shot had some blurring (I think from subject movement) at the higher location, and we wanted to be able to compare regions that were sharp in all examples. This doesn't have much impact on the conclusions about noise though, because the lighter regions here are about the same brightness as the darker regions of the previous crops.)
I have to admit that the results above were a bit of a shock. At low ISOs, Adobe Camera Raw blows away the in-camera JPEGs, but at high ISOs, it's entirely the other way around. Thinking that I was just getting too aggressive with the noise reduction controls in ACR, I processed the ISO 6400 file with both luminance and chroma noise sliders set to zero. As you can see from the results, the detail loss is still pretty horrific.
Some readers have reported that this is a known behavior of ACR with CMOS sensors. I haven't studied the issue to know whether that's true or not, but it's apparent from the crops above that there's some pretty extensive noise processing going on somewhere, outside the control of ACR's noise reduction sliders.
At the time of its announcement, Sony touted the fact that the A700 was doing noise reduction on the raw image data, before it was written to the RAW format. I'd hoped that what we're seeing above is simply a matter of not being able to fully disable the anti-noise processing in ACR, and not a result of NR that's being done in-camera prior to the RAW file being written. If the latter is the case, it really defeats the purpose of a RAW file, and would mean that the detail would be forever lost to post-processing.
There's always a question of what's really in a RAW file, as there always has to be at least some processing done to convert it for viewing on an RGB display. In an attempt to get at least one more data point for what's going on in the A700's RAW files at high ISO, I converted a file in Sony's own Image Data Converter, with the noise-reduction processing option turned off. The results can be seen in the bottom right crop in the table above, and seem to support the idea that the noise reduction (and detail loss) is indeed present in the RAW files themselves.
More on Noise Reduction in RAW files
After posting all the above images, a reader asked the (should have been obvious) question of what setting of the High-ISO Noise Reduction option they were shot with. - And whether that setting would affect the RAW files as well. The images were shot with the camera's default NR setting, and to see whether that would affect the RAW files, we shot (yet another series), this time of the Still Life target, at ISO settings between 1600 and 6400, and with all three high-ISO NR settings (low, medium, and high). (We're beginning to feel that there's no end to testing the A700!) Crops from these shots are shown below (we'll include links to the files themselves, but they'll be uploading and synchronizing between our servers for a little while yet, so for now are only posting the crops.)
|High_ISO NR examples (all crops at ISO 3200)|
|High||Medium||Low||Low, via ACR|
As you can see from the examples, the High-ISO Noise Reduction option clearly affects the contents of the RAW files pretty drastically. Given the above, I may try reshooting RAWs of the Indoor Portrait test, with High-ISO NR set to low. No promises as to time frame though, the A700 is now way over the limit of time we can really afford to devote to a single camera.
I'll try to come back and report more on all this, once Bibble gets its translator done or when I get a copy of Capture One able to read the A700's files. (Although as noted, we're getting pretty far beyond the amount of time we can legitimately allocate to the A700, we have many other cameras piling up awaiting testing.)
Extremes: Sunlit and low light tests
High resolution with good overall detail, but slightly high default contrast. Good low-light performance, but with some exposure variation.
|Default Exposure||+0.3 EV||+0.7 EV|
The Sony Alpha A700 performed quite well under the deliberately harsh lighting of this test, though contrast was a little high at its default setting. As mentioned previously however, the camera's contrast adjustment did a better than average job of handling the harsh lighting, and even at the default contrast setting, detail was preserved quite well in the white shirt. Though the shirt looks blown at +0.3 EV at default contrast, there's actually good detail there, a welcome change from many cameras' handling of this test. (In "real life" though, be sure to use fill flash in situations like the one shown above; it's better to shoot in the shade when possible.)
We really like it when a camera gives us the ability to adjust contrast and saturation to our liking. It's even better when those adjustments cover a useful range, in steps small enough to allow for precise tweaks. Just as with its saturation adjustment, the Sony A700's contrast setting meets both challenges.
|Minimum Contrast, normal D-R setting|
|Contrast set to lowest,
|Contrast set to lowest,
At its lowest contrast setting, the A700 did an excellent job of preserving highlight detail, maintaining natural-looking skin tones, and holding nice detail in the shadows. The A700 captures good color outdoors, though just slightly on the warm side. Overall, very good results here, especially when the contrast setting is tweaked.
|Contrast Adjustment Examples|
The series of shots above shows results with several different saturation adjustment settings, showing the minimum step size around the default, as well as both extremes. While you can see the extremes, it's hard to really evaluate contrast on small thumbnails like these, click on any thumbnail to go to the full-size image.
One very nice feature of Sony's contrast adjustment is that it has very little effect on color saturation. Contrast and saturation are actually fairly closely coupled, it's a good trick to be able to vary one with out the other changing as well. Sony did a good job here.
|Highlight Detail vs Contrast, normal D-R setting|
|Default Contrast||Default Contrast
|Lowest Contrast||Lowest Contrast
As I mentioned above, even the default contrast and D-R settings (more on D-R shortly), the Sony A700 held perfect highlight detail in Marti's shirt, even though it looked blown out. To better show this, the above show unaltered images on the left, and ones processed in Photoshop to stretch the highlights to cover most of the tonal scale. (I boosted the midtone slider in Photoshop's Levels control to a gamma setting of 0.25.) The first pair of crops show results with the camera's default contrast setting, the second shows highlight results with the lowest contrast setting.
Interestingly, after the extreme gamma shift above, the image shot with the lowest contrast setting actually shows more contrast in the highlights. What's up with that? The reason for this is that the low contrast setting has pulled the entire highlight end of the tone curve closer to the midtones, so there's more room to record variations between subtle highlight tones, hence the greater apparent contrast there after the gamma adjustment.
|Shadow Detail vs Contrast Setting|
|Default Contrast||Lowest Contrast
slight subject differences)
The impact of the contrast adjustment was even more evident at the shadow end of the tone scale, the lowest contrast setting did quite a bit to brighten the dark shadows. The two crops above are from two separate frames, one shot at the default, the other at the lowest contrast setting. The two photos unfortunately aren't exactly identical, Marti's hand position is a bit different between the two. (One of the downsides of a live model, I've tried to get Marti to wear a straightjacket, but she just refuses. ;-) The areas of the crop are quite equivalent in terms of light levels though.
Sony's DRO (Dynamic Range Optimization)
While the Sony A700's contrast adjustment feature works very well, their Dynamic Range Optimization system is a critical part of it. This system analyzes the range of brightness of each image, and adjusts the camera's image processing parameters accordingly, to make the best use of the available dynamic range. Four options are available, DRO Off, Standard D-R, D-R+, and D-R Advanced, which lets you choose between 5 levels of strength for the D-R Plus effect. Standard D-R looks at the entire image and effectively adjusts contrast and brightness across the entire image for best effect. D-R+ analyzes everything, but makes local adjustments to bring out shadow detail and preserve highlights.
We saw DRO in the Sony A100 last year, and found that it worked fairly well, but we really wished there was an option to adjust the strength of the effect in D-R+ mode. It seems the Sony engineers were listening, because that's exactly what they gave us this time around.
|DRO Off||DRO Standard
|DRO Advanced +5
The crops above show the results of four DRO settings. They were shot in rapid succession, but astute readers will notice that minor movements by Marti mean that the shots aren't absolutely identical. The cropped areas are very closely equivalent in terms of light level though. As you can see, the bulk of the difference between different levels of DRO is found in the shadow areas. By default, the A700 shoots with DRO set to the Standard (D-R) level. Interestingly, there's a pretty pronounced difference between DRO Standard and Off, in terms of exposure. I confirmed that the shots above were all captured with the same aperture and shutter speed settings, but the DRO Standard version is a good 2/3 of a stop or so lighter than the shot with DRO turned off entirely.
As noted, we felt that DRO in the A100 had some limitations, but the technology seems to have matured very nicely in the intervening time since that model was introduced. It works well enough and with little enough impact on normally-lit subjects that I'd be entirely comfortable leaving it in Standard mode all the time. (Sony obviously felt so too (since it's on by default), but it's unusual that I personally would be comfortable leaving an image-tweaking option enabled by default.) And it's nice that Sony listened to our plea to make DRO adjustable. The Advanced option gives 5 gradations, giving you a very nice range of control over its application.
|DRO Advanced Mode Adjustment Examples|
Note: Because digital cameras are more like slide film than negative film (in that they tend to have a more limited tonal range), we test them in the harshest situations to see how they handle scenes with bright highlights and dark shadows, as well as what kind of sensitivity they have in low light. The shot above is designed to mimic the very harsh, contrasty effect of direct noonday sunlight, a very tough challenge for most digital cameras. (You can read details of this test here.)
Low light: The Sony A700 did fairly well in our low light test, but at the very lowest light levels, its meter underexposed the shot slightly at all ISO settings. ISO 1600 shots were pretty clean across the board, ISO 3200 was noticeably noisy but probably usable for many applications, and ISO 6400 was noisy to the point that we'd probably not use it except for 4x6 inch prints.
Interestingly, noise didn't increase much at all as the exposure time was increased, with noise levels in the darkest shots not being far different from the noise in much shorter exposures. We also found little difference at the exposure times we used here with the long-exposure noise reduction on or off. Playing around with the camera later, we were surprised by how little noise was present in even 5-minute exposures. When we went to 10 minutes at ISO 100, noise became pretty high when the long-exposure noise reduction was turned off, but with it on, the images were surprisingly clean. (The Sony A700 uses a dark-frame subtraction method for long-exposure noise reduction, so a 10-minute exposure with NR enabled means your camera will be tied up for a total of 20 minutes before you'll be able to see the captured image.)
The Sony A700 focused quite well (of not a little slowly) in dim lighting as well, its AF system operating down to a bit under 1/8 foot-candle with the AF-assist light turned off, and in total darkness with it enabled.
How bright is this? The one foot-candle light level that this test begins at roughly corresponds to the brightness of typical city street-lighting at night. Cameras performing well at that should be able to snap good-looking photos of street-lit scenes.
NOTE: This low light test is conducted with a stationary subject, and the camera mounted on a sturdy tripod. Most digital cameras will fail miserably when faced with a moving subject in dim lighting. (For example, a child's ballet recital or a holiday pageant in a gymnasium.) For such applications, you may have better luck with a digital SLR camera like the Sony A700, but even there, you'll likely need to set the focus manually.
Good print quality, accurate color, good 13x19 inch prints from in-camera JPEGs, excellent ones from carefully-processed RAW files. RAW images capable of making good-looking 20x30 inch prints with little trouble. In-camera JPEGs are sharp at 8x10 inches to ISO 1,600.
Testing hundreds of digital cameras, we've found that you can only tell just so much about a camera's image quality by viewing its images on-screen. Ultimately, there's no substitute for printing a lot of images and examining them closely. For this reason, we now routinely print sample images from the cameras we test on our Canon PRO9000 studio printer, and on the Canon iP5200 here in the office. (See the Canon PRO9000 review for details on that model.)
When its USB interface is set to PTP mode, the Sony A700 supports direct printing (no computer required) to PictBridge compatible photo printers. The extent of PictBridge support varies greatly between cameras, and the Sony A700's support is better than many, but not quite as robust as we remember from the A100. Provided that it's connected to a printer that offers an equivalent level of support and control, you can select batch printing either singly or in 1-up, 2-up, or 4-up layouts or an index print, paper size, bordered or borderless prints, and time/date imprint options directly from the camera's menu system. (Pretty slick.) Printing via PictBridge to our Canon PRO9000 studio printer , we found it to be a little slow in formatting and preparing the data to send to the printer, but significantly better than the A100. (It took 1 minute and 30 seconds to print a 4x6 photo at best quality, more than twice as fast as the A100.)
The Sony A700 certainly has plenty of resolution to make great-looking enlargements straight from the camera: 13x19 inch prints looked good in areas of high contrast, but regions of subtle contrast looked mushy and soft. Images we processed from its RAW files (via Photoshop and Adobe Camera Raw version 4.2, the best RAW converter we had that would read the A700's files at the time of this writing) showed incredible detail, holding together exceptionally well even at 20x30 inches.
As always, the biggest challenge was at high ISO, and there the A700 faltered slightly, but once again di better than the A100. Noise and softening from the anti-noise processing are well-balanced, but there's more of both than we'd like to see at the highest ISOs. Shots at ISO 1600 look fine up to 8x10 inches (a full stop improvement over the earlier A100's images), but ISO 3200 images are softer, and at ISO 6400, image noise was quite obtrusive. On a positive note though, color held up pretty well even at ISO 6400, but oddly was slightly more muted at ISO 3200.
While the shots at ISO 6400 were quite noisy, many users will be satisfied with 5x7 inch prints for display on wall or table, and 4x6 inch prints are likely to be acceptable to most.
Color-wise, the Sony A700 did pretty well, in that its photos were generally hue-accurate and appropriately saturated, perhaps a little brighter overall than the A100's images, something we think will help them appeal to a broader audience. (And the A700's saturation adjustment has nice fine steps on it, so you can easily tweak the camera's color up or down to match your personal preferences.) All in all, a very good performance. -- But serious shooters will definitely want to work from the A700's RAW files.
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