nex7 aa filter removed compared to DP2M

Started Aug 22, 2012 | Discussions thread
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docmaas Veteran Member • Posts: 5,930
nex7 aa filter removed compared to DP2M

This is kind of a funky comparison because I'm using the Sigma 30mm f2.8 on the nex and the built in 30mm on the DP2M. The nex image is also bigger and is resized down for comparison purposes.

First on the lenses. It is impossible to separate out the lens from the sensor but I find the Sigma DP2M lens to produce better images from f2.8 to f8 than the Sigma 30mm f2.8 EX for the Nex camera. They appear to be equal in the center but the edges go to the DP2M without question. The 30mm EX lens is not bad at all, it's very respectable but it isn't the equal of the DP2M lens on the edges. Even at f2.8 the DP2M lens is sharp all the way across the image on a flat target and of course gets better through f5.6 then declines due to diffraction at f8.

I had originally intended to do a lot of tests but I am finding the DP2M so much better in resolution than the Nex 7 I don't think it is necessary to test much more.

These are images of the same piece of a rock shelf at the beach. First the sony Nex 7 image was resized down to match the Sigma image size. Then a small patch of the image is doubled in size 3 times so the final comparison images are magnified to 8x their actual size. All the enlarging was done with Irfanview using the lanczos algorithm.

A couple of other things. I think the Nex 7 is more sensitive to diffraction than the DP2M. This is quite likely due to the smaller pixels. The difference in appearance between f5.6 and f8 on the NEX seems significantly more noticeable on the NEX than on the DP2M.

Second, the more the images are enlarged the more you can see how the NEX image with the Bayer filter begins to fall apart and degrade. It's not important to images at normal sizes, those look fine, but it is evidence that there is a significant difference between the two technologies. Moreover the finer the detail at the most minute levels, the better the information and resolution at the visible level of the final image.

I can't quantify the difference between the two cameras but I can say I find the DP2M images to be more satisfying to my eye by a significant margin.

Here are the images

The first image is an unmodified jpg from the DP2M with sharpening set at 0:

The second is the same image with sharpening set to -2 in spp resulting in no sharpening.

The third image is an unsharpened jpg processed in Photoshop CS 5 with sharpening turned off:

and finally the fourth image is the jpg as it comes out of the NEX7 unmodified.

It's pretty obvious at this level of magnification why the Sigma produces better images. What is surprising is how the unsharpened Sigma image seems at some level sharper than the sharpened image. When viewed at normal size the sharpened image is noticeably sharper but when magnified the sharpened image actually seems to have lost detail compared to the unsharpened image. Much of the fine structure has been smoothed out. To me this is counterintuitive.

As far as the nex images go, it's pretty obvious that some sharpening is happening in the camera. The unsharpened image out of photoshop is considerably less sharp than the image that came straight out of the camera.

Removing the AA filter has not brought the Sony to the level of quality I was hoping for when compared to the Sigma. It is of course, still a fine camera but not as good as the Sigma where the Sigma is usable. The Nex cameras while not perfect are better at high iso and are much faster and more facile instruments.


Panasonic Lumix DMC-F5 Sigma DP2 Sony Alpha NEX-7
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