Sony A350: Full-Time Live View at 14.2MP
by Wesley Fink on April 3, 2008 3:00 AM EST- Posted in
- Digital Camera
Resolution, Sensitivity and Image Quality
Sony likely wanted to scoop the industry with the 14.2MP resolution of the entry A350. That plan probably got scrapped by the 14.6MP Samsung CMOS sensor used in the prosumer Pentax K20D. While the A350 doesn't gain bragging rights as the highest res sensor south of $8000 it is still mighty close at 14.2MP. It is also the highest resolution sensor to be found in any current or announced entry-level DSLR.
Pentax went to great lengths to emphasize the greater size of their photoreceptor sites that made sensitivity more akin to the Sony/Nikon 12MP sensor. Pentax also emphasized the expanded sensitivity of their 14.6MP sensor with ISO options to 6400. Sony makes no special claims for the 14.2MP sensor in the A350, but the new sensor still has the option of ISOs to 3200.
We've already discussed how the A350 is easy to use with the best Live View you can find in a DSLR these days. The big remaining question, then, is whether the 14.2MP sensor really makes any difference in image quality.
To answer that question we considered that the most revealing test of sensitivity, noise, and resolution is low tungsten light typical of home interiors. The selected scene was not chosen to be pretty but to be revealing of sensitivity, noise, and image quality. It is a shot of my office stacked with motherboards and other review equipment taken with a standard 50mm f1.4 lens.
We found the APS-C 14.6MP CMOS sensor in the Pentax K20D to be excellent in sensitivity with well-controlled noise. The sensor size and resolution is roughly comparable to the A350, but the camera is much more expensive, uses a CMOS sensor rather than CCD, and it is targeted at the prosumer rather than entry-level. For those reasons, we included the Pentax K20D in these comparison tests.
The Canon 5D is justifiably famous for its incredible resolution with the full-frame 12.2MP CMOS sensor. The larger size sensor creates larger photo sites and the larger pixels are more sensitive to light than smaller APS-C sensors. The larger sensor size means the pixel size is more like an 8MP APS-C than a 12.2MP sensor. That makes for a good comparison to these two 14+MP sensors.
All images used a 50mm f1.4 lens (Pentax 50mm f1.4, Sony/Minolta 50mm f1.4, Canon Ultrasonic 50mm f1.4). Aperture Priority was used with a fixed aperture of f4 at all ISOs on all three cameras. Shots were taken using a tripod and remote shutter release to prevent shake. High ISO Noise Reduction used the lowest level of high ISO NR that could be selected in each camera. White Balance was manually set to Tungsten on each camera and the only light source is a 100W tungsten bulb. These harsh test conditions should make image noise as severe as you will likely see in each camera short of time-exposure darkness. Images were captured in JPEG format so they could be displayed and downloaded without the requirement for post-processing software.
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haplo602 - Friday, April 4, 2008 - link
Well done on the reshot. The only one lacking is the Canon 5D (should be the same image area) but other than that, quite fine.I read through almost all the comment pages and I have a few things to add.
AT is a page for geeks and enthusiasts that want the best tool for the job. In this case mostly a gaming rig (AT still has gaps in OS, server, workstation reviews). I noticed that you do not want to mimic the other established sites. The problem is, there is not much choice.
The camera models differ in details that are largely unimportant to the usual AT visitor. And you cannot expect people to ditch an SRL system when they got more than just body+kit lense.
So I suggest you pick a place that covers what the average AT visitor wants to know - make a POLL/survey about that.
Pixel peeping is not for normal people. They shoot at max ISO 800 (or whatever the auto iso setting will max at). Mostly leave the photos in digital form to present on web galleries. Hardly anybody does larger prints (beyond 10x15 cm photo). BUT I think they are concerned about ease of use, good camera manual, availability of accessories (lenses, flashes etc.), performance in mostly auto or program mode, JPEG quality and such.
These are the areas AT should work on. Hardly any serious photo site does review the automated or (idiot) scene modes.
Truth is, whoever does use scene modes on an SLR shoudl be still using a point and shoot, but there is a group of people that are not satisfied with the limits of P&S cameras, yet they have not mastered the science behind photography. These will be interested in the areas I just mentioned.
I'd say give it a thought, do a review based on that and see the reactions ...
Wesley Fink - Friday, April 4, 2008 - link
Since I have had several requests for same "field of view" images and crops for the Canon 5D I have added a page 7 with two sets of Canon 5D crops and full images.One set is taken from the same location with the 50mm lens. That is the set that was already in the updated review an it provides a greater field of view on the 5D than on the 1.5X multiplier cameras.
The second set of 5D images were shot with the same camera and 50mm lens moved closer to the image to try to maintain the same field of view. Despite the different fields of view, all Canon 5D cropped images are still maintained at 230x300 pixels.
With both sets of Canon 5D images you should be able to compare the A350 and Canon 5D images as you would like to see them compared.
danddon - Friday, April 4, 2008 - link
Thank you for correcting this issue. These crops are better, but not the areas are still identical in size. Perhaps you can improve in your next set.Now, then - how about some comments on photosite size discrepancies between the a350 and 5D? Since the 5D has a larger sensor, with a smaller number of pixels, the photosites are correspondingly larger. Hence, for any given light level, these photosites will gather more photons than the a350. This will result in a higher signal to noise ratio, with less noise appearing in the crop.
Since you are fond of not getting too technical, let's say the photosites are twice as large in the 5D. If so, then should we not be comparing, say, the iso3200 on the 5D with the iso1600 on the a350?
If you do not like the above numbers, please give us unwashed readers your take on how to account for these differences in sensor sizes. Surely, you want to provide this analysis. Yes?
Wesley Fink - Friday, April 4, 2008 - link
Since we are still dealing with different sensor resolutions, the same field of view will yield slightly different crops since we are maintaining the same pixel crop size of 230x300. The Canon 5D is 12.2 megapixels and the Sony is 14.2 megapixels. So a same-size crop from an equivalent field of view image on the Canon 5D would still show more area than the same pixel-size crop from the higher resolution A350. To produce same pixel-size crops and take this into account would take endless manipulation with each camera tested that had a different sensor resolution or multiplier.The Pentax K20D at 14.6 and the Sony at 14.2 are closer in resolution so the differences are not as great, but there are still differences in the same pixel crops. As we would expect the Sony crop view is a bit wider since it is a bit lower in resolution than the Pentax.
We could just crop the same area from equivalent field of view photos, as I have seen done in some other photo reviews. However, it is my opinion that is not a fair representation of noise since the crop areas would represent different total pixels. This becomes an interesting problem when you compare a 10 megapixel sensor since the resolution is almost 50% less than the Pentax K20D.
danddon - Friday, April 4, 2008 - link
How about the issue of photosite size?From “Digital Photography Review”:
Canon 5D
Sensor Size = 35.8mm x 23.9 mm
Max Image = 4368 x 2912 pixels
Alpha 350
Sensor Size = 23.6mm x 15.8 mm
Max Image = 4592 x 3056 pixels
Assuming the above numbers are in the ballpark, we get a photosite maximum possible size of:
5D = 35.8/4368 = 8.196 or 8 microns
23.9/2912 = 8.207 or 8 microns
a350 = 23.6/4592 = 5.139 or 5 microns
15.8/3056 = 5.170 or 5 microns
Thus the 5D has a photosite area of 8x8 or 64 sq. microns
Likewise, the a350 has an area of 5x5 or 25 sq. microns
If we ignore the reductions in these areas due to photosite boundaries, which would be required for light shielding between sites and for electronics, then we can say that the 5D has approximately 2.5 times more photosite area than the a350.
Thus, everything else being equal and for the same iso setting, the 5D will gather 2.5 times more photons than the a350, with a correspondingly better signal to noise ratio, and less visible noise in the resulting image.
Therefore, why should one compare iso3200 on the a350 with iso3200 on the 5D, when the 5d would receive 2.5 times more photons in each photosite? Please explain.
Wesley Fink - Friday, April 4, 2008 - link
First of all the photosite size for the K20D does not scale as you indicate. One of the Samsung/Pentax big deals is that they say they have reduced the space between photosites to increase the size. They claim the 14.6 megapixel sensor has about the same size photosites as the Sony A700/Canon A300 12.2 megapixel sensor.All else being equal the photosite size obviously matters, but all else is never equal. You can can compare the photos and crops for yourself in this review instead of calculating what should and should not be compared. As I have learned in reviewing computer components, assumptions and suppositions often get you in trouble.
danddon - Friday, April 4, 2008 - link
Then how does it scale? How about some math instead of words?And who even mentioned the K20D? The comparison being discussed is between the a350 and the 5D. Can you read?
LOL ...
I have heard enough. And, it was far too little to be of any value. Thanks, anyway.
danddon - Friday, April 4, 2008 - link
This sentence:"These crops are better, but not the areas are still identical in size."
should read:
"These crops are better, but not the image areas are still not identical in size."
Sorry for the confusion. My bad.
danddon - Friday, April 4, 2008 - link
This sentence:"These crops are better, but not the areas are still identical in size."
should read:
"These crops are better, but the image areas are still not identical in size."
Sorry for the confusion. My bad - 2.
Maxington - Friday, April 4, 2008 - link
Just keep improving your reviews and listening to constructive comments Wesley. I appreciate a different take on reviews regardless, you always have to read multiple reviews from multiple people to get a proper take on a product. All of them cover a different aspect that the others didn't take into account.There is no perfect way to review cameras, have you seen the DPReview forums? They are pretty much the gold standard for reviews, and after every review, there are dozens of threads decrying the obvious flaws in the testing system! You can't win again people who are far more interested in measurebating the tech specs than taking photos, and there is no way to remove all variances between different cameras, let alone entire brands.
I tend to feel there is a lot less bias in your reviews than most "camera" sites. A lot of those smack of "If its not Canon/Nikon, its not a camera".
Hell, most of the issues that the measurebater crowd are niggling at won't even be visible in real life photos.