[Digitalis]

@Digitalis, did you see a "you have been quoted / mentioned" notification on your control panel when I named you before? (I am wondering if that acutally works like that)

yes,I did.

regarding diffraction, why is it shows it´s effect at different f-stops on different lenses with the same focal length?

No it doesn't, diffraction affects all lenses equally - the sensor resolution only makes its effects more apparent as the pixel density gets higher.

Would you say f/22 is the absolut limit for APS-C 16Mpx sensors? I mean, if I needed the depth of field f/22 will deliver, Would I be better off using f/11 because diffraction efect will be worse than out of focus blur?

It really depends on what size you are printing the image. With a 16Mp sensor an image taken at f/29 printed at 8"X12" would look basically indistinguishable from an image printed at 8"X12" with the lens at f/8. But if you printed at 24"X36" the image with the lens stopped down to f/8 would look sharper than the image taken at f/29.

There are some photographers who use near-far compositions that find it easier to stack multiple images taken at a lenses optimal aperture in order to extend DOF, there are also tilt/shift lenses that are able to mimic large format camera movements and give you the ability to extend DOF without needing to stop the lens down as much - and thus staying under the diffraction limit.

[nomadkng]

digitalis, i'm going have to respectfully disagree with your statement that diffraction affects all lenses equally.

https://en.wikipedia.org/wiki/Airy_Disk

I'm posting the link, because all the heavy lifting has been done for me. Far field diffraction (aka Airy Disk) equations bear out the math that actual physical lens construction will have an effect on diffraction, making it more pronounced or less evident.

yes, light is light and it will be defracted the same way around/through openings, but lenses (more specifically their openings) vary in multitudes of ways. the simplest example: f4 in a medium format 15mm lens is not the same as f4 on a dedicated aps-c 15mm lens. Thus the construction of the lens can mitigate some effects of diffraction if that's part of the basis of design

[Digitalis]

light is light and it will be defracted(sic) the same way around/through openings, but lenses (more specifically their openings) vary in multitudes of ways. the simplest example: f4 in a medium format 15mm lens is not the same as f4 on a dedicated aps-c 15mm lens. Thus the construction of the lens can mitigate some effects of diffraction if that's part of the basis of design

I was keeping this discussion constrained to the relevant format: which is APS-C. And for our purposes diffraction begins to be visible in images under close scrutiny, at f/8~f/11 aperture range. Beyond that range accutance in the image will be reduced. The bottom line is that a 15mm f/4 lens* will be subject to diffraction way no matter which format sensor is behind it or how well designed the lens is. However the format of the sensor hides the effects of diffraction because the ratio of magnification of each image - a Medium format image has to be enlarged much less than an APS-C image for an 24"X32" print. This is what makes it difficult to notice the effects of diffraction on different formats, and why Ansel Adams was quite happy to shoot at f/64 most of the time, even when he had large format view camera with movements what would have allowed him to use a wider aperture. Because on an 8X10 contact print no one could see the effects of diffraction, even on a 16X20 - a 2X enlargement from an 8X10 negative, you still wouldn't be able to see it. Only when you start getting into the 6~10X magnification range, issues like diffraction can become visibly problematic - but in all my years I have rarely been required to make such massive prints from 8X10 format.

There are precious few diffraction limited lenses for 35mm cameras - nearly all of them are 100mm and over. Though I am certain no manufacturer has ever made a diffraction limited 15mm f/4 lens, not one.

* i'm not speaking in equivalent terms here.

[stevebrot]

Honestly, microcontrast and coloring can all be done in Lightroom in a few seconds.

Ummmm...you can't enhance what is not there. Enhancement of either of the above in LR will very quickly result in artifact if not done judiciously. There are practical limits as to what can be done to overcome image deficiencies in software. As the saying goes..."Garbage in...Garbage out".

I am a fan of the 18-55 kit and have done some pretty good work with mine. I have also shot briefly with the DA 15 Limited and, as noted above, the difference is immediately apparent both in terms of quality and FOV.


Steve

[NitroDC]

Ummmm...you can't enhance what is not there. Enhancement of either of the above in LR will very quickly result in artifact if not done judiciously. There are practical limits as to what can be done to overcome image deficiencies in software. As the saying goes..."Garbage in...Garbage out".

I am a fan of the 18-55 kit and have done some pretty good work with mine. I have also shot briefly with the DA 15 Limited and, as noted above, the difference is immediately apparent both in terms of quality and FOV.


Steve

Microcontrast: clarity
Color: saturation/vibrance, contrast, and hue shifting.

I'm not pulling this out of nowhere, I own both lenses. I own the FIRST version of the kit lens (inferior to the current WR one). If you bothered reading anything else from my post, you would have realized that I stated exactly what you said above.

[stevebrot]

...If you bothered reading anything else from my post, you would have realized that I stated exactly what you said above...

If so, I guess we are in agreement.


Steve

[Digitalis]

There are practical limits as to what can be done to overcome image deficiencies in software. As the saying goes..."Garbage in...Garbage out".

I agree, contrary to your statement Nitro: the crude tool referred to as Clarity in lightroom only affects macrocontrast. Microcontrast is something different altogether*. If everyone could manipulate the levels of microcontrast in post processing then why do we elevate certain lenses above others for this characteristic? A lens simply has it or it doesn't.

* If you photographed a white cat against snow in broad sunlight, a lens with reduced microcontrast would have difficulty separating the subject from from its surroundings. A lens with High micro-contrast would be able to separate the similar tones of subject and background and thus deliver a more pleasing rendering.

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Last edited by Digitalis; 06-23-2013 at 07:11 AM.

[NitroDC]

I agree, contrary to your statement Nitro: the crude tool referred to as Clarity in lightroom only affects macrocontrast. Microcontrast is something different altogether*. If everyone could manipulate the levels of microcontrast in post processing then why do we elevate certain lenses above others for this characteristic? A lens simply has it or it doesn't.

* If you photographed a white cat against snow in broad sunlight, a lens with reduced microcontrast would would have difficulty separating the subject from from its surroundings. A lens with High micro-contrast would be able to separate the similar tones of subject and background and thus deliver a more pleasing rendering.

I understand, but I guarantee you if I take a shot at 31mm with the kit lens at f/5.6 and do the same shot on an FA31 (possibly the most sought after Pentax prime ever?) and spend a little time editing the kit lens shot, I could get a very similar result to the FA31 image (in terms of color ONLY). However, the sharpness, bokeh, and overall rendering of the image would stay and the FA31 would obviously still be better. I know some lenses have more "transparency" and others are sharp around edges and soft in more solid areas. These kinds of things are difficult to replicate in lightroom/photoshop, and usually end up looking a little fake.

What I'm trying to say here is that every lens has its purpose, but you shouldn't seek a lens purely for its color rendering, because in this day and age, those kinds of things are very easy to modify without "artifacts". If you're more of an out-of-the-box shooter (do little, if any, editing) then I totally understand the appeal of a lens with more contrast. My F50/M50 lenses have a TON of microcontrast compared to my kit lens, but even then, some quick exposure brushing and contrast in LR will gain similar results from the kit lens.

So getting back on topic, to me, the 15mm was worth it over my kit lens. Not for its color rendering, but its focal length, flare resistance and sharpness. And it's super fun to shoot with.