All Forum Comments
Comment by froeschle posted on Photos of and with the GR... at 11/10/2013 - 10:58
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Yeah, I guess you know why this happens with this camera...
Yes, because of the lack of a Bayer-AA filter.Yeah, I guess you know why this happens with this camera...
There have been reports that it is quite unlikely that one runs into problems.
Therefore I tried to provoke color moiré.
https://www.pentaxuser.com/forum/topic/k5-2s-moire-just-for-the-record-43272/p-3#comm485874
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There are ways around it though. Obviously you can correct it using the in-camera moire correction but you can also stop it occurring by using an aperture of f10 or smaller.
Not always and not with this pattern.There are ways around it though. Obviously you can correct it using the in-camera moire correction but you can also stop it occurring by using an aperture of f10 or smaller.
The in-camera moire correction fails: http://forum.digitalfotonetz.de/viewtopic.php?p=1313593#1313593
Try to correct it by yourself (note that this is an irregular repetition of a single small rectangle).
I am quite convinced that this is not so easy.
The original looks everywhere like the bottom of the left printout.
I shortly discussed there, why moiré occurs only "partially" (in German):
http://forum.digitalfotonetz.de/viewtopic.php?p=1313976#1313976
Btw, artefacts are visible also at f11.
However, you are right that smaller and larger apertures make it less apparent.
Changing subject distance also has an influence.
My point here is that the lack of a Bayer-AA filter can sometimes completely ruin your picture...
...or create Modern Art .
Comment by froeschle posted on Photos of and with the GR... at 11/10/2013 - 10:04
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using the GR, which has the same size sensor and also no AA filter, there has been no sign at all of moire
I currently test a Ricoh GR from Pentax/Ricoh Germany.using the GR, which has the same size sensor and also no AA filter, there has been no sign at all of moire
As the weather is not really good here, I also have looked at color moiré.
Imho, it was quite easy to provoke problems:
https://www.pentaxuser.com/forum/topic/photos-of-and-with-the-gr----44957#comm485868
Comment by froeschle posted on K5 2S moire-Just for the record at 10/10/2013 - 20:38
Modern Art
Comment by froeschle posted on Photos of and with the GR... at 10/10/2013 - 20:17
Comment by froeschle posted on Photos of and with the GR... at 08/10/2013 - 17:10
The easiest procedure would be to meter at maximum aperture first.
Then set the aperture to its desired value, i.e. stop down (e.g. 3 stops).
Use the first measurement and apply the necessary compensation (here: 3 stops).
Then set the aperture to its desired value, i.e. stop down (e.g. 3 stops).
Use the first measurement and apply the necessary compensation (here: 3 stops).
Comment by froeschle posted on Exposure issues with older manual lenses at 26/09/2013 - 16:29
Old wisdom is still true .
A negligible investment would heal the problem.
Btw, the Nikon D7000[7100] offers this feature, which the K-5 [II(s)] still lacks.
A negligible investment would heal the problem.
Btw, the Nikon D7000[7100] offers this feature, which the K-5 [II(s)] still lacks.
Comment by froeschle posted on Exposure issues with older manual lenses at 26/09/2013 - 13:12
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It is quibbling a bit though, isn't it? It isn't a problem with A lenses and later if they are used in the way that the bodies were designed for them to be used.
I don't think so. I agree with Bojidar Dimitrov:It is quibbling a bit though, isn't it? It isn't a problem with A lenses and later if they are used in the way that the bodies were designed for them to be used.
http://kmp.bdimitrov.de/technology/K-mount/crippled_AF.html
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The only reason for the existence of this mount variation is cost cutting. This was achieved by leaving out the stop-down coupler of the body mount and the aperture ring of the lens mount. With this move Pentax sacrificed one of its strongest advantages, the unrivaled K-mount compatibility.
The only reason for the existence of this mount variation is cost cutting. This was achieved by leaving out the stop-down coupler of the body mount and the aperture ring of the lens mount. With this move Pentax sacrificed one of its strongest advantages, the unrivaled K-mount compatibility.
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When I first started using lenses where the body controlled the aperture I thought it was a step backwards, but actually it's just the same thing. It doesn't matter what the method is as long as it's efficient.
I like the "two wheel" approach (since the Z-1P) as a possible alternative, though.When I first started using lenses where the body controlled the aperture I thought it was a step backwards, but actually it's just the same thing. It doesn't matter what the method is as long as it's efficient.
E.g. setting the aperture at the aperture ring, the shutter speed with the front wheel and ISO with the rear wheel would also be a good option.
With an aperture coupler in the bodies one also could use P-TTL with M lenses.
So, the crippling of the mount leads to less options and restricts usage.
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Having said that, if the cameras allowed normal use of M and K lenses I would be more inclined to use them. As it is, I don't see the point as current lenses are as good, sometimes better. Unless of course we want to experiment, and that's something else entirely.
Turning this argument around, I would state that lots of M lenses are (at least) on par with current (zoom) lenses.Having said that, if the cameras allowed normal use of M and K lenses I would be more inclined to use them. As it is, I don't see the point as current lenses are as good, sometimes better. Unless of course we want to experiment, and that's something else entirely.
There should e.g. be no noticable difference in optic performance of M 50/1.7, A 50/1.7, FA 50/1.7, DA 50/1.8.
But there is a difference in price.
So, allowing full functionality (of M lenses) could harm sales of new lenses.
Comment by froeschle posted on Exposure issues with older manual lenses at 26/09/2013 - 12:41
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Sorry, froeschle, I don't get what you mean here.
Try to find an optimal/balanced/compromised setting (aperture, shutter speed, ISO) in M mode by looking at the histogram. Keep this setting while shooting. Even this should be more reliable than the usage of the green button.Sorry, froeschle, I don't get what you mean here.
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From the stuff you quote about the red curve and the blue curve, am I right in thinking that with A lenses, and the lens set at A, the exposures should be correct, and that the only problem is with M lenses (of which my 300mm is unfortunately an example)?
Not fully.From the stuff you quote about the red curve and the blue curve, am I right in thinking that with A lenses, and the lens set at A, the exposures should be correct, and that the only problem is with M lenses (of which my 300mm is unfortunately an example)?
With an A lens, and the lens set at A, exposure is OK.
Now use one and the same lens.
With this A lens, and the lens now set at a fixed aperture (e.g. f11) and with usage of the green button, exposure is unreliable.
So, exposure is inconsistent if you set the aperture manually with the aperture ring (A, F, FA, DFA etc. lenses).
This is due to the fact that DSLRs are optimized to meter at maximum aperture.
In contrast, the green button method performs measurements at working aperture.
This results in inaccuracies (depending on lens, focal length, aperture, body, etc.).
So, the problem is not restricted to M lenses.
The cause is the missing aperture coupler in the bodies.
This problem could be fixed by de-crippling the K-mount in future cameras.
Comment by froeschle posted on Exposure issues with older manual lenses at 26/09/2013 - 12:10
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I wonder has anyone catalogued their own experiences with this somewhere?
Yes, unfortunately the diagrams have been removed (in German dfn):I wonder has anyone catalogued their own experiences with this somewhere?
http://www.pentaxforums.com/forums/pentax-dslr-discussion/200075-pentax-ricoh-de...#post2113449
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Test procedure: An image of a white area was taken with an A-lens and a K-5 at several f-stops (x-axis), the grey scale value of the image then was determined with Photoshop (y-axis).
Blue curve: Lens set to A, aperture value set in camera (which would be similar to the usage of an uncrippled mount).
Red curve: Aperture value set at lens, usage of green button (note the deviation from the blue curve and/or a constant value: the fluctuations correspond to about two f-stops -> predictiveness?)
http://forum.digitalfotonetz.de/viewtopic.php?t=82962Test procedure: An image of a white area was taken with an A-lens and a K-5 at several f-stops (x-axis), the grey scale value of the image then was determined with Photoshop (y-axis).
Blue curve: Lens set to A, aperture value set in camera (which would be similar to the usage of an uncrippled mount).
Red curve: Aperture value set at lens, usage of green button (note the deviation from the blue curve and/or a constant value: the fluctuations correspond to about two f-stops -> predictiveness?)
Fluctuations [!] of about two [!] f-stops.
Quote:
[...] test shots [...] birds [...]
Look at the histogram and stay at the same settings after optimisation...[...] test shots [...] birds [...]
Comment by froeschle posted on Exposure issues with older manual lenses at 26/09/2013 - 10:54
To be fair, it is a very extreme example in choice of subject.
But it was easier than I thought.
With this image I wonder if you would not see some moire even with an AA filter?
As I discussed shortly in one of the links (in German), you cannot prominently see color moiré everywhere in the picture.
This is due to the fact that the wall and the camera were not fully parallel.
Furthermore, each print was only fixed by one adhesive tape.
So, not everything is in perfect focus.
This tiny bit of "blurring" (which normally is the purpose of the Bayer-AA filter) is enough to make the pattern (nearly) disappear (see bottom part of left print-out and left part of right print-out).
To correct it though I would think about converting to black and white, or even shooting in black and white. Have you tried this approach, and if so does it help?
Convert the above picture into grayscale or black and white, you will see that this is not sufficient.
Shooting in black and white is not really possible, as the original color (Bayer) output will only be converted.
So, these two approaches are not so different after all.
Thus, more photoshopping would be required.