[Klaus]

http://www.imatest.com/docs/sharpness.html#calc

[Klaus]

http://www.imatest.com/docs/sharpness.html#calc



It's not my claim - I'm just a user actually. :-)

[awaldram]

[quote name='Klaus' timestamp='1290776738' post='4476']

http://www.imatest.com/docs/sharpness.html#calc



It's not my claim - I'm just a user actually. :-)

[/quote]

Ah there pre-stacking using multiple copies of different blur levels.



"The four bins are combined to calculate an averaged 4x oversampled edge. This allows analysis of spatial frequencies beyond the normal Nyquist frequency."



Not sure I agree with their conclusion though especially given their own corrections.

"Correction 11/22/05: the bin does not depend on the detected edge location."



But the maths is beginning to go above my head <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/blink.gif' class='bbc_emoticon' alt=':blink:' />

[Steinar1]

[quote name='Klaus' timestamp='1290773926' post='4470']

Regarding Nyquist - you can look a bit beyond the barrier if you're test target is known. You cannot if you've no idea of what you're measuring of course. The K10D does naturally not deliver a resolution beyond that - especially considering Bayer. It's just about measuring a lens potential (FWIW, the big one provides resolution figures beyond Nyquist in their lens tests as well).

I will certainly not go into the details of the local testing procedure. Leave us our little secrets, please. :-) However, the basic procedure is described at imatest.com. Their documentation is very extensive and their method is used across the whole industry (including the some of the camera manufacturers). They also describe a little how they can measure beyond Nyquist if you're interested.

I reckon that the resolution numbers are not overly accurate anymore beyond Nyquist but that's my personal guess here.



As far as "false detail" is concerned:

http://www.maxmax.com/nikon_d200hr.htm

http://www.maxmax.com/nikon_d300HR.htm

http://www.maxmax.com/nikon_d700hr.htm



There's certainly some amount of false details in the "hot rod" versions. However, there's also a fair amount of extra detail as far as I can tell. Sharpening during post-processing will not recover all this and it would just come at cost of more noise anyway.



Just to clarify this - I DO NOT RECOMMEND THIS TO NORMAL USERS and most will not invest the bucks anyway.



And another note - I'm just guessing that the K5 has a strong AA filter. The "softness" may also originate in RAW NR. Only Pentax does not for sure (so far).



And one more - I know Falk personally. He lives just around the corner actually. A highly knowledgeable guy and I agree with him about the AA. The question is about the thickness, not about its existence. I would, of course, prefer to have some sort of AA filter like e.g. in the Pana G series. This is preferable to none at all. However, I doubt that a very strong AA filter is the right solution. The service company will "exchange" the AA filter so they'll not just remove it - they claim a gain of effective resolution of 30% max. so I suspect that there's still some filtering in there.

[/quote]



Hi Klaus

I read the article and info on the HR conversions wih interest. You say you do not recommend it to normal users. Why not? The increase in sharpness on my D300s seems fantastic. Are there disadvantages, beyond the price? Kidly Vieux Loup

[Klaus]

[quote name='Vieux loup' timestamp='1290779588' post='4478']

Hi Klaus

I read the article and info on the HR conversions wih interest. You say you do not recommend it to normal users. Why not? The increase in sharpness on my D300s seems fantastic. Are there disadvantages, beyond the price? Kidly Vieux Loup

[/quote]



Have a look at the Oly sample image:

http://photozone.smugmug.com/photos/551754081_WwNJs-O.jpg



In the middle portion of the image there's a roof top with some kind of fine rock gravel:

You can spot some funny colors in there (probably a demosaicing effect in conjunction with the excessive resolution).

In the maxmax samples you should also be able to find some moirees in the artificial test targets.

Often this is not disturbing but it can be a show-stopper - e.g. macro photography, bird feathers, hairs - things that are "stacked" and "straight".

[Class A]

[quote name='Klaus' timestamp='1290776634' post='4475']

http://www.imatest.com/docs/sharpness.html#calc

[/quote]

Thanks. It appears they are aiming at sub-pixel precision by exploiting blur distribution.



Do you know to what extent their approach depends on the assumption of adequate anti-aliasing, i.e., the presence of an AA filter?



Is it possible that feeding the Imatest software with images from a sensor with no AA filter might produce questionable results and/or what precautions have to be taken to make sure that this doesn't happen?

[Klaus]

[quote name='Class A' timestamp='1290803667' post='4481']

Thanks. It appears they are aiming at sub-pixel precision by exploiting blur distribution.



Do you know to what extent their approach depends on the assumption of adequate anti-aliasing, i.e., the presence of an AA filter?



Is it possible that feeding the Imatest software with images from a sensor with no AA filter might produce questionable results and/or what precautions have to be taken to make sure that this doesn't happen?

[/quote]





They offer test data for phone cams so I reckon there's no need for an AA filter (but phone cam optics serve as a AA filter for sure).



However, we've fed Leica M files into Imatest and the results are reasonable (unless you apply "normal" sharpening - the absolute values skyrocket in this case).

[Guest]

[quote name='Class A' timestamp='1290765043' post='4461']

AA filter strength is certainly not a matter of taste.[/quote]



Just out of curiosity - what do think of 645D then?

[Class A]

[quote name='Lomskij' timestamp='1290818994' post='4483']

Just out of curiosity - what do think of 645D then?

[/quote]

Great camera. You can order it with or without AA filter.



Here's a quote by Falk Lumo: "But as long as uneducated photographers cry for a weak or no AA filter the industry will listen and give us dirty colors in fine textures. Thank's everybody." In the same post he says "No AA filter means lot's of ugly color moiré and artifacts. The appearant softness from an AA filter is easily removed with an USM radius 0.5 filter.".



It would be great if he could join this discussion or have a chat with Klaus.



I don't know about others but I'd love to hear more from Klaus about justifying his statements about the K10D vs the K-5. It still doesn't add up for me.

[Klaus]

[quote name='Class A' timestamp='1290847093' post='4487']

Great camera. You can order it with or without AA filter.



Here's a quote by Falk Lumo: "[url="http://www.pentaxforums.com/forums/pentax-news-rumors/103935-pma-australia-speaks-21mp-pentax-6.html#post1072295"]But as long as uneducated photographers cry for a weak or no AA filter the industry will listen and give us dirty colors in fine textures. Thank's everybody.[/url]" In the same post he says "No AA filter means lot's of ugly color moiré and artifacts. The appearant softness from an AA filter is easily removed with an USM radius 0.5 filter.".



It would be great if he could join this discussion or have a chat with Klaus.



I don't know about others but I'd love to hear more from Klaus about justifying his statements about the K10D vs the K-5. It still doesn't add up for me.

[/quote]



I'm already discussing with him under the hood.

A USM of 0.5 produces sharpening halos and increased noise as well as reduced (unrecoverable) micro contrast. This is hardly a non-lossy approach and whether this is any better than a rare false color pattern (of a weak AA filter) is debatable. It is, of course, a matter of taste whether you'd like to go left or right here. Frankly the industry should simply offer two, possibly three versions of a camera with different AA filters setups - they do so in the 645D, fine, do it for consumer DSLRs as well, please. The extra production costs for this would be next to zero and consumers could simply choose according to their preferences.