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Sony Cyber-shot DSC-F707

Wow! 5 megapixels, a super-sharp lens, Hologram AF, NightShot, NightFraming and more! Killer technology, great photos from Sony!

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Page 12:Test Results & Conclusion

Review First Posted: 08/20/2001 (Full production model update 11/20/2001)

Test Results
In keeping with our standard policy, my comments here are rather condensed, summarizing my key findings. For a full commentary on each of the test images, see the DSC-F707's "pictures" page.

As with all Imaging Resource camera tests, I encourage you to let your own eyes be the judge of how well the devices performed. Explore the images on the pictures page, to see how well the F707 performed, and how its images compare to other cameras you may be considering buying.

Wow! The DSC-F707 figuratively knocked my socks off with its resolution and image quality: While it's important to note that there's a lot more to the F707 story than "just" image quality (what with NightFraming, Hologram AF, etc), the camera surely delivers in that department. In virtually every parameter, the F707 delivered outstanding images: Hue, saturation, tone, noise, and resolution were all excellent. On my "Davebox" test target, the F707 reproduced the subtle pastels accurately, handled the often-difficult red/magenta separation with ease, and showed excellent hue accuracy and saturation on the large primary color blocks. It also handled the difficult blue colors of the flowers and model's pants on the Outdoor Portrait test well, with only a slight tendency to shift those colors to purple, as so many digicams seem to do. Overall, it's hard to find any fault with the F707's color handling in any circumstance.

The camera's white balance system also deserves special mention, as I found it very accurate under a wide variety of circumstances. The prototype F707 I tested showed some tendency to introduce a greenish tinge when using the Automatic white balance setting, but that defect appears to be entirely corrected in the production firmware. In particular, I was impressed by how well the automatic white balance option did on the tough "Indoor Portrait" test. Many cameras have a hard time with incandescent room lighting, although those with manual white balance options generally manage to get a decent exposure. Cameras' automatic white balance systems almost never manage to neutralize the heavy yellow cast of the room lighting though. I was thus very surprised that the F707 in fact produced a nearly perfect shot with the auto white balance option selected.

As just noted, the slightly cyan/green cast to the images shot under outdoor lighting with the prototype seems to be comletely cured in the production firmware. Readers have written to ask me if I'd seen an over-saturation in reds reported by some reviewers. I didn't notice this the first time around, but looked back over the test results to see what I could find. Interestingly, it does seem that the F707 over-saturates very strong reds, but curiously, this doesn't seem to affect more pastel shades. Of the shots I normally take, only the red roses in the outdoor portrait shot looked too strong, any other shades of red looked quite OK. (For instance, both the skin tones and the pink flower in the outdoor shot look very natural.) In revisiting this topic with the production F707, it looked to me like the oversaturation wasn't quite as pronounced, but was still there. As noted though, it seems to only affect red hues that are highly saturated, the effect not extending into more pastel or less saturated shades. (Thanks to reader Wade Hathaway for the forum query asking me about this issue.)

WIth its 5 megapixel CCD and razor-sharp Carl Zeiss lens, resolution is a big part of the F707's story. As you might expect, it performed superbly on my "laboratory" resolution test chart. While minor artifacts crept in at spatial frequencies as low as 1,000 lines per picture height, I found "strong detail" out to 1,200 lines (!) both horizontally and vertically, and "extinction" of the target patterns didn't occur until about 1,650 lines (I dropped both those numbers slightly after scrutinizing the shots from the production camera. They're still very good resolution numbers though.) Throughout all of my testing, I found exceptional detail, even in the difficult shrubbery of the House poster and the outdoor far-field shot.

Actually, the F707's resolution comes close to the very best I've seen from any digicam I've tested, at any price point. How close? Check out the comparison below. (Click to see a full-sized version.) This is a direct comparison between a F707 and Nikon D1X pro SLR, my current "reference standard" for image resolution (and most any other image-quality parameter) among the cameras I've tested. (Note: To head off the inevitable emails, no, I haven't tested the Kodak DSC760 6 megapixel pro SLR yet, so can't comment on its resolution.)

 

 

Because the two cameras' in-camera sharpening is so different, I've shown comparisons with the default sharpening, and then with the images shot with in-camera sharpening off and unsharp masking applied in Photoshop. The results are interesting, to say the least. To my eyes, the D1X wins for sharpness and clarity (an ill-defined term meant here to indicate that it simply looks like I can see more detail more clearly in the D1X image). It's impressive just how closely the F707 matches the D1X's resolution though: If your budget is less than a thousand dollars, and you need maximum resolution and detail, the F707 is the camera to get.

Optical distortion on the F707 was a bit higher than I expected. At wide angle, barrel distortion is about average, at 0.74 percent. The telephoto end was slightly better, but showed 0.55 percent pincushion distortion, a bit more than average among the cameras I've tested. (To be fair though, the other cameras mostly have 3x zoom lenses, not the 5x of the F707.) Chromatic aberration was also a bit higher than I'd like to see, although better than average among long-zoom digicams. I saw 2-3 pixels of color on either side of the target lines on the resolution target. I saw this some in shots of trees against bright sky, as the long-familiar "purple plague" syndrome, with purple highlights around dark areas, shooting against bright backgrounds. The purple plague wasn't as bad as I've seen on some cameras but definitely still there. (Frankly, there's only one or two cameras on the market that seem to manage to avoid this, so no big demerits for Sony on this score. I'd sure like to see digicam manufacturers address this problem though...)

 

 

With full manual exposure control and a maximum shutter speed of 30 seconds, the F707 handles low-light shooting with ease. Not only that, but noise levels are amazingly low! The crop above is taken from a shot at 1/16 foot-candle (*0.687 lux), a full three stops down from typical city streetlighting. While the prototype camera required some color-correction, the shot above from the production model has had no tonal or color correction applied to it. (! - This level of color rendition at this low a light level is quite rare in my experience.)This was a 20 second exposure at ISO 100! Frankly, there are some cameras with this much noise in broad daylight. Needless to say, the F707 produced clear, bright, usable images down to about 1/16 foot-candle (or 0.67 lux) with good color at all three ISO settings. The camera's Auto white balance had some difficulty adjusting the color balance at the lower light levels, but began accurately processing the scene at 1/4 foot-candle (2.7 lux). The F707 automatically employs a Noise Reduction system at shutter speeds slower than two seconds, which did an excellent job of keeping noise in check. Even at ISO 400, noise was very minimal. The hologram AF is another big plus for low light shooting - the camera focused perfectly at all light levels, including pitch blackness. Really an amazing low-light machine!

Actually, noise (or the lack of it) is an important part of the F707 story. Buried in the Sony specs was mention of "ClearColor Noise Reduction." I'd noticed that the F707's images seemed to be very low noise, whether shooting at low light (as above), or in daylight. I asked Sony what ClearColor NR was all about, and were intrigued by the answer. Apparently, the F707 processes chrominance and luminance separately in the camera electronics, before combining them to produce the RGB data recorded in the file. (This is a video processing trick, so no surprise to find it in a Sony camera, given Sony's looong experience in broadcast video.) What the ClearColor trick is about is that the camera leaves the luminance signal alone (preserving detail that our eyes are sensitive to), but closely examines the chrominance data. Wherever the difference in chrominance from one pixel to the next is less than a certain threshold, the camera "flattens" the chrominance, eliminating noise that exists solely in the color channel. The chrominance and luminance signals are then combined and separated into RGB components. (Actually, I suspect what happens is a lot more sophisticated than what I just described. For instance (for those readers into image processing), I expect that what's used is some sort of a median-filter kernel, as opposed to a simple thresholding.) Regardless of the specifics, the results are pretty amazing: The F707 has lower image noise than any camera I've tested, with the sole exception of the Nikon D1X. (One wonders if Nikon might not be using this sort of approach in the D1X as well...) - And yes, that includes cameras like the Canon G2, which offer an ISO50 option: The F707 at ISO 100 is actually "cleaner."

 

 

I thought some of our readers would be interested in seeing actual noise measurement results from three four cameras noted for their low noise: The new Canon G2 (an excellent performer in this respect), the F707, the Nikon D1X, and the Canon D30. The screen shot above shows the histogram display from Photoshop. Four options are available, showing histograms for luminosity and the R, G, and B color channels. To perform the test, I selected 90x90 pixel blocks from a flat tint from the MacBeth chart on the Davebox target, and looked at the stats. Here's what I found:

 

Digital Camera Noise Figures (brightness units, 0-255)
Camera
Lum.
Red
Green
Blue
Canon G2, ISO 100
2.23
3.00
2.44
3.05
Canon G2, ISO 50
1.51
2.18
1.73
2.42
Sony DSC-F707 ISO 100
1.30
1.94
1.49
1.65
Nikon D1X, ISO 125
1.17
1.29
1.23
1.49
Canon D30, ISO 100
0.79
1.31
1.03
1.27

 

UPDATE: Reader Cinstance Chen called us rather severely to task for leaving out the Canon D30 from the comparison, as that camera is widely recognized as being at the top of the market in terms of noise performance. Cinstance was absolutely right in doing so, I'd totally overlooked the D30, it having been a year since I reviewed it. In fact, the D30 does do quite a bit better than even the D1X, making the F707 the *third* best camera noise-wise that I've tested. (At least, so I think, the noise measurement is a new one I'm experimenting with, so I don't have a lot of historical data for it.) The general conclusion still stands though, buyers of the F707 aren't giving up anything in noise performance simply because the camera lacks an ISO 50 setting. (In the rumor frenzy leading up to the F707's announcement, the lack of an ISO 50 option was voiced by some as a strike against the F707. I didn't find this to be the case.)

UPDATE #2: (Dave here.) Reader Bryan Siverly wrote to say that he had both a Canon G2 and a Sony F707 in his posession, and was considering returning the 707 because its shadow noise was noticeably higher. This was very interesting because the noise measurements I took (see above) showed the 707 having lower noise than the G2, not higher. When I looked in the deep shadows of the Davebox, and at the darker swatches of the MacBeth and grayscale targets, I did indeed see more noise there than in the midtone regions. It appears that the 707 delivers excellent noise levels at roughly midtone and brighter levels, but does less well in deep shadows. It seems that a complete characterization of image noise will really require measurements at shadow, midtone, and highlight brightness values. For now, the 707 does seem to fare a bit worse than the G2 in deep shadows, but I didn't think it was overall too bad in that respect.

UPDATE based on production model 707: Measuring the noise levels on the darkest swatch of the MacBeth chart in the Davebox target, the F707's noise at ISO 100 does in fact appear to be slightly higher than that of the G2 at ISO 100, and a fair bit higher than the G2 shooting at ISO 50. Interestingly, at ISO 100, the F707's luminance noise is actually lower than that of the G2 (standard deviation of 1.59 vs 1.7), but the noise in each of the individual color channels is higher. This can be seen in the illustration at right: These crops are from the ISO 100 Davebox tests, with a pretty extreme gamma boost (2.8) applied in Photoshop. The shadows on the G2 shot are a bit grainier and more mottled looking (higher luminance noise), but the F707's show more coloration (higher color noise). This is all probably a bit overwrought, as both cameras do very well in the noise department, but I thought it important to qualify my earlier effusive enthusiasm over the F707's noise performance, to incorporate Bryan Siverly's observations about shadow noise levels, and place the whole issue fully in context.

The F707's electronic "optical" viewfinder is very accurate, showing approximately 98 frame accuracy at both wide angle and telephoto lens settings. Therear-panel LCD monitor is also very accurate, showing approximately 97 percent of the image area at the wide angle setting, and approximately 98 percent at telephoto. Given that I generally prefer LCD monitors to be as close to 100 percent accuracy as possible, the F707's LCD monitor performs well here (and the electronic viewfinder isn't too shabby either, since it's essentially a miniature version of the LCD monitor).

The F707 captures a very tiny macro area, among the smallest I've seen at just 1.68 x 1.26 inches (42.79 x 32.19 millimeters). (Although not the smallest, that honor still goes to the Nikon 995.) Resolution was again very high, though the sharpest details were in the center of the frame, on the dollar bill. The brooch and coin details were very soft due to a limited depth of field up that close, and there seemed to be quite a bit of curvature of field. (Corners were rather soft.) Because of its position and the huge lens cross-section, the F707's flash really doesn't work up close: Figure on getting an external flash or using floods for macro shooting.

While its NightShot, NightFraming, and Hologram AF capabilities put it in a class of one, the F707's image quality really raises the bar on the rest of the prosumer camera field. Without question, its resolution and color rival those of vastly more expensive professional products. When I looked at the first test shots, I could hardly believe the level of detail I could see in them, and its low noise levels were a big surprise as well. Although I had a few minor quibbles here and there, the DSC-F707 really sets a new standard for prosumer digicam performance. VERY highly recommended!


Conclusion
My tests of a production model F707 only confirmed the high opinion I'd developed of the camera based on my testing of a prototype. By any measure, the DSC-F707 is an impressive addition to Sony's digicam line, with exciting innovations in focusing technology, including the NightShot and NightFraming functions, as well as the Hologram Autofocus system. The F707 captures truly excellent color and image quality, thanks to its 5.02-megapixel CCD, and has enough exposure control and features to appeal even to professional photographers. (Its resolution is actually very much on a par with the Nikon D1X, my personal benchmark for the state of the art in pro SLRs.) Its lens is topnotch, producing tack-sharp images from corner to corner (although I did find a little chromatic aberration). Novice users will appreciate the Program AE and preset Scene shooting modes, in which the camera chooses all exposure settings, while still giving them plenty of room to grow into the camera. With everything it has going for it, the F707 should do very well in the market. Highly recommended, and big kudos to Sony for the focus innovations!

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