Sony A77 sensor reports – Is sensor size more important than MP today?

Started Oct 4, 2011 | Discussions thread
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Ma55l
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Sony A77 sensor reports – Is sensor size more important than MP today?
Oct 4, 2011

“Popular Photography” magazine tests many cameras and is a highly respected source of information.

They rate image quality and how high iso can be pushed and still maintain the resultant best image quality. The ratings and testing are published once per month. The current report using a production Sony A77 with V1.02 which is the latest firmware was able to achieve an Excellent image quality rating but only up to iso 400.

I have only seen four categories used to describe the image quality of cameras in almost three years of reporting (from Jan 2009 until present) in that magazine. The quality levels are from best to worst, Excellent, Extremely high, Very high, and High. I think of them as Excellent = A, Extremely High = B, Very High = C and High = D, as that is the tier order for image quality. I have not seen a poor rating.

Including their current publication now on the internet for the A77 test (go to popphoto.com) and over the past almost three years, only 10 cameras have achieved the top A or Excellent classifications at any iso. The rating as mentioned also show how far up the iso scale one can go and still maintain the excellent classification. All the other tested cameras cannot reach the excellent classification at any iso –including the D300s, Canon 7D, Nikon D7000 and D 5100 as well as many others.

For instance, the Nikon D3X, 24 MP Full Frame can maintain an Excellent Image category rating up to iso 3200. Although this camera is very expensive the results show that it is technically possible to attain that result with a 24 MP full frame camera. The far less expensive Canon 5D MKII, 21 MP is the same – excellent image quality to iso 3200. The Sony 850 and 900 achieve that Excellent rating thru iso 1600.

But the Sony A77 can only do that up to iso 400 and so is in the lowest iso category for Excellent image quality range.

Some interesting observations. From checking the results in the issues of “Pop Photo”; no 14 MP or less camera has achieved an excellent image quality rating with the current rating system (seems that 2400 lines is the minimum for an excellent rating). Two were 15 MP sensors but those two like the Sony a77 did not penetrate farther than iso 400 at the excellent image quality tier. Any sensor with 18 MP or more always attained an excellent mark for image quality but only 3 of 4 18 MP cameras could raise their iso to 800 for that level and one was the same as the Sony only able to get to iso 400. It would seem from this that a 15MP APS camera can equal the A77 image and up to the same iso rating.

According to “Pop Photo tests” the Sony A77 at iso 100 will only resolve 2770 lines while the three full frame 24 MP cameras all achieve 3200 lines at 100 iso. In addition all the 24 MP full frame units can maintain an excellent image rating to iso 1600 or 3200 (that is - with four to eight times less light than the A77). Even the Eos 5D mark II full frame at 21 MP will maintain an excellent image rating up to and including iso 3200. But the Sony A77 can only retain its excellent image rating to iso 400.

Before you discredit the above as meaningless, consider how much more effective a two (iso 400 compared to 1600) to three stop (iso 400 to 3200) is in photography. Three stops is like increasing your F stop from 5.6 to F 2.0. How much money extra would you have to pay to increase the F stop of all your lenses to get a 2 to 3 stop advantage? If you were shooting in night portrait mode instead of a shutter speed of 1/8 second which would likely be blurred you could shoot at 1/64 second which would be sharp (all other factors being equal). And you could shoot at F 5.6 instead of F 2.0 and so get to a better and sharper aperture for the lens. That in effect would make the Nikon 200mm F 2.0 IS at $7,000 not needed in comparison to a run of the mill 200mm 5.6 lens to get a low light image properly exposed. Also what about considerations for sports.

I personally feel that at 24 MP on an APS sensor, the manufacturer has surpassed the point of diminishing returns in comparison to a full sized sensor of the same number or fewer megapixels (as in 21.1 for the Canon). If you can recall your high school/college days you will remember that a light microscope can only achieve 1,000 times magnification and that only with using an oil emersion lens. That is the limit for magnification for a light microscope because of the physics of light. You might recall your teachers calling any larger magnification “empty magnification” since no further detail can be resolved.

24 MP on an APS sensor is in that category now where the physics of light are becoming a limiting factor. In addition recall the same number of megapixels on the A77 APS sensor resolves 400 to 500 lines less than the resolution in any of the three 24 MP Full Frame cameras, and that from processing engines that are three or more years old - before the newest processing technology was available.

So with these considerations in mind, I would prefer an 18 MP sensor over 24 MP on an APS platform. But clearly the best would be a 24 MP to 30 MP on a full frame sensor. Lets dream about the near future.

Some people will notice in the following posts, that there appears to be a pack of dogs mentality promoted by some chronic repeat posters who have nothing positive or of value to say about anything. These posters have finely tuned sarcasm and play off one another as if everything is a joke to try to demean the true concerns and perspectives of the many people who would like to post – but don’t voice their concerns because of the dog pack. Please ignore their repetitive add nothing condescending remarks and please report what you think is bad behavior to abuse@dpreview.com or in the provided feedback section page link to contact Dpreview. I feel, you can disagree but you don’t have to be disagreeable. We should act as adults.

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