A77 sensor dissapointing at high iso - new images

Started Sep 13, 2011 | Discussions thread
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Ma55l Contributing Member • Posts: 805
A77 sensor dissapointing at high iso - new images

A 580 vs A77 at iso 3200.

Please open the comparison photo to full size by clicking on the image so that a valid comparison can be made.

This is a new image comparing the A77 24 MP sensor to the A580 16 MP sensor. Both are APS size and are at iso 3200. From conventional wisdom (which I want to challenge here) one might think that the A77 sensor should be able to capture and retain fine detail better, have higher resolution and because of the advances in technology have lower noise than the A580 sensor. That is clearly true at low iso’s like 100 and I do not challenge that, but what about at higher iso? Do the troubles with smaller photosites in the 24MP sensor have drawbacks that actually make performance inferior to a 16 MP sensor at high iso and if so what are the differences?

It has been my contention that a 24 MP APS sensor’s photosites are too small to adequately process the noise generated by and with the enormous amplification needed for low light. This side by side comparison clearly shows that at iso 3200 the 24 MP A77 sensor not only has more noise (look at the supposedly clear fluid in the bottle to see the noise) but also note the superior resolution and retention of fine detail by the A580 (look at the printing on the label). Notice the retention of the smooth texture of the label by the A580’s sensor while the A77’s rendition looks rippled or crumbled as if it had been removed and reglued to the bottle. And lastly notice a small amount of white at the border of the letters and printing in the A77’s image which is not present or less intense in the A580 image. For those that are not aware those changes (brightness at the edges of borders) are usually a sign of oversharpening. And although sharpening makes the image looks sharper (artificially) it can not increase fine detail. To be fair the extra sharpening could also be easily applied to the A580 image to give more snap - but in the A77 it cannot be undone or removed.

So I feel that at high iso, the A580 16 MP sensor outperforms the A77 24MP sensor in regards to:
1. preservation of fine detail,
2. visible noise,
3. resolution, and

4. at the same time the A580 sensor has lower image processing distortions. (not to be confused with lens distortions.) see example image below showing sensor/processor distortions.

This image is from the internet and made by the A77 at iso 1000 during outdoor daylight, showing the lower rim of an eyeglass melting into the fellow's face as well as the severe texture distortion of the man's skin. The image is at 100% and with no manipultions here. Those skin changes are not real unless perhaps he has Leprosy. Personally I would not think a professional photographer would want to submit this photo as representative of his work or his abilities.

To make my self clear here – I do not think the A77 has a poor sensor, only that it could be a lot better, especially since a 16 MP APS unit can run circles around it at iso 3200, and that in every parameter regarding an image’s quality or truthfulness of reproduction.

One last point - for those that think this is pixel peeping - no pixels can be seen.

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