Hi,
It's not clear what is depending on lens, pixel size and AA filtering. One thing that is pretty clear is that AA-filtered images require much more capture sharpening than images without AA-filters, normally small radius and high amount. I normally use Lightroom and use radius < 1, amount around 40 and detail slider fully to right. That's pretty much OK on the Alpha 900 but excessive on the Alpha SLT55 which seems to have a weaker AA-filtering.
Another issue is lenses. Leica lenses are renown for uncompromising quality comparing a Sony ZA zoom with a Leica prime having twice the price may put the Sony at disadvantage. The Leica has also larger pixels, so if we would compare the image at actual pixels the Leica would have a significant advantage in MTF, like 15% higher MTF. That advantage would go away if the images were scaled to match.
One issue with aliasing is that it results in fake detail. With the Bayer matrix, normally used on DSLRs it causes obvious colorful Moiré patterns, but the fake details may also be perceived as better contrast.
A very good example of fake resolution is here:
, note that at around 18 the lines disappear but at 22 they are back, but being fewer. This is typical of images without OLP filtering where the lens has significant MTF at the Nyquist limit. The image links to the DPReview test of the Sigma DP2, a camera with Foevon sensor and not having OLP filter.
I made a comparison of sample images from the Leica S2 and the Nikon D3X by Lloyd Chambers. Lloyd is painstaking in his testing, so the images were probably as close as possible in field shoots. My findings are here:
http://echophoto.dnsalias.net/ekr/index.php/photoarticles/38-observations-on-leica-s2-raw-images .
So, I would say the issue is complex. OLP filtering is technically necessary but removing it leaves more MTF at fine detail in the image. That MTF will normally results in artificial detail, which may seem to enhance the image. OLP filtering needs some aggressive extra sharpening. Sharpening would also enhance noise, so we may need extra noise reduction. Stopping down f/11 may reduce AA-effects significantly.
I have also seen really bad Moiré in a Pentax 645D sample shot
. That article is here:
http://echophoto.dnsalias.net/ekr/index.php/photoarticles/51-a-closer-look-at-pentax-645d-image-qualityMoiré or not I would be interested of the Pentax 645D, except that I don't really have the money to burn, but also for weight reasons. I'd need a lot of lenses to replace my 135 equipment. Flying with a significant photographic equipment is a real challenge.
Best regards
Erik
I really think so.
I recently decided to downsize from medium format digital back to 35mm. I am getting older and I simply couldn't easily carry my MFD kit around any more. (for those interested I was using a Hasselblad H4D-50 and half a dozen lenses, filters, batteries etc but it could easily have been another system). I decided to buy a Nikon D3X with a few lenses as my "serious" outfit and a Leica M9 for walkabout and holidays. The Nikon is a nice camera, no question, but I just couldn't get to like the images. After the Hasselblad they seemed somehow soft and lacking punch, bite whatever. The M9 on the other hand was like a mini-Hasselblad, sharp as a tack and a joy to use.
Last year I used a Sony A900 for a month and liked the combination of the sensor and the Zeiss lenses so I sold the Nikon and bought a Sony outfit (not too bad on Ebay). Again I found myself comparing the output from the Sony unfavourably against the M9 and indeed the Hasselblad. It is now up for sale.
My position seems to be that once I had moved from 35mm digital (Canon and Nikon) to MFD I not only gained some megapixels (no big deal) but more importantly lost that damn AA filter and I can't go back.
If Leica can make a camera without an AA filter in 35mm format why cannot Nikon/Sony/Canon? It seems to be that it is now redundant for cameras with 18-25 megapixel sensors. Am I wrong, am I missing something, or what?
What do you all think?