Sony A77 disappointing sensor vs 12 MP Sony a700.

Started Oct 29, 2011 | Discussions thread
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Ma55l Contributing Member • Posts: 805
Sony A77 disappointing sensor vs 12 MP Sony a700.

This thread is primarily meant for a700 users. It shows what differences to expect in images at high iso vs. the a77.

I have written about and showed images of the Sony A77’s disappointing results at high iso compared to many other cameras. I feel that a 3-4 micron pixel (size of bacteria, smaller than red blood cells) is just too small to gather enough light to produce good effects in low light. At iso 100 it is fine.

Below, I show an iso 3200 image from the a77 against a Sony a700 @ iso 6400 image.

I feel the images from the A77 are deficient in detail at elevated isos in comparison to cameras that have 3-12 million fewer pixels. Dpreview in their just out full official review of the a77 (at this site) feels the same way - see their conclusions re: image quality where they use the term “Mushy JPEG Rendering”.

The demon is noise at high iso. That is generated by the required enormous amounts of amplification needed because tiny pixels can’t gather much light. The same happens when listening to the radio with a small antenna – NOISE!

It is possible to electronically process images and trade fine detail for less noise by averaging contiguous pixels. You can do that easily in Photoshop. In the past a 10/12 MP camera would not get heavily into that trade off. But the a77 starts with 24MP and so there is some leeway to trade noise for detail at high iso. But has Sony gone too far in that trade off - trying to make the reported noise values for the a77, as tested by independent testing sites, look better than it should, but detail is trounced.

There are 2 100% crops below: one from my Sony a700 at iso 6400 taken with a Sigma 18-200 @ 200mm F6.3 - wide opened where its performance is lowest. The a77’s image is at iso 3200 - twice the light of the a700 image.

I downsized both full images to 600 pixels highlighting the areas to be shown at a 100%. The 100% crops are undisturbed.

Each of us has different wants and needs for a camera. My point here is to demonstrate to a700 owners how much and what the difference looks like on your computer as well as on your a700 LCD. I will restrict my opinions here only to detail and noise at high iso.

I know these images are of different scenes and this is not a purely scientific test, but I think you can easily see what to expect from each camera. I tried to use crops representing about 1/6 of the diameter of each full image. That is the size displayed on the LCD when you push the enlarge function once in the a700. This is not pixel peeping. The image in the a77 is inscribed on approximately twice as many pixels as on the a700 and with twice the light and therefore should have dramatically more detail. Both are handheld, without flash. Please click on each image below.

The a77 100% crop below shows severe obliteration of fine detail in the lady’s hair. Strands are matted together, look smudged and are almost unrecognizable. Large areas of fine detail are replaced with a large uniform patches of color. That is typical of small pixels, on small real estate at high iso. Please click but don't gasp.

On the other hand the different scene from the 12MP, APS, a700 shows terrible noise but there is retention of fine detail as the bar code stripes and numbers are clearly recognized and without linear distortions in spite of the fact that the a700 image is taken in half the light. From viewing many other a77 images at iso 1600 to 6400, I feel confident that none of the detail or numbers resolved by the a700 at iso 6400 would be understandable in the a77 even at iso 1600.

To prove that, here is a comparative side by side image by the A77 at iso 1600 vs. 100. The iso 1600 image shows the lettering at the top of the card is unrecognizable. As always please click the image to get the comparison right.

At iso 100 the lettering is understandable. But the a700 image above shows even smaller lettering clearly at iso 6400. (Also note the linear distortion with the a77 at 1600 vs. 100).

If half the megapixels (12 vs. 24) can resolve more detail at high iso and DXO states that anything above 8MP is unneeded, why are we pushing for 24 MP in the first place?

DXO states that 8 MP on an APS framework will produce a retina sharp 8x10 print at 14 inch viewing distance. The limitation is the human eye and not the print. A 24 MP sensor should provide more detail than a 12 as twice as many pixels are assigned to the image. In reality, less or the same image detail will be seen at EVERY iso for the a77 on an 8 x 10 print. The reason is that the extra 12 MP of the a77will not make that print sharper at 14 inch viewing distance at any iso, but high iso favors detail in the 12 MP image. Why are we going backwards to 24 MP?

Some would say “What about a mural” – no one views a 10 foot mural at 14 inch distance. It would still appear perfectly sharp. For instance the best HDTV image 1920 by 1080 is a 2 MP image but appears tack sharp at 6 feet away.

The a700 uses old processing routines. The same sensor with newer routines would retain that detail with less noise. My preference is to keep my A700. I can tolerate noise much better than loss of detail. And I can do noise reduction in post processing to the level and fashion that I want.

I can wait for an upcoming full frame 18 to 32 MP camera. Then we will have the best of everything – resolution, detail, low distortion, saturation, noise and the narrow depth of field of full frame. Apparently Canon agrees - EOS 1D X their 18 MP upcoming flagship camera.

One last photo (a77, v1.02, iso 1,000, full daylight). The distortions here can be seen on an 8 x 10 print. If that is OK the a77 is for you.

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