edge artifact & moire with K20D...

*janosh* · 10-28-2009, 10:55 AM

Shots of dark mountains at far distance in very clear, bright scenes with clear dark sky backgrounds behind the mts sometimes/often have the fine, white edge outline that typically comes from over-sharpening. I always shoot RAW. Is there a way to eliminate that outline in post-processing or in camera (staying in RAW). I shoot RAW primarily because I'm seriously into printing, which means post-processing.. JPEG simply doesn't cut it.

Also with K20D, fine details, such as skinny white sticks/vines or tall fine grass in big scenes, sometimes show moire. Is there a way to kill that in post processing? (I've just seen a worse moire with Canon 5DII, so that's not the answer I thought it might be.. the older version 5D hasn't shown the problem in the prints I've seen... I don't think the older FF 5D has any detail resolution advantage over K20D, though it may be a little "smoother" in some situations).

Anybody run into and/or solve these issues in their printing?

*Wheatfield* · 10-28-2009, 11:06 AM

This sounds more like a raw converter problem, although moire can really be a problem with cameras with weaker AA filters. Unfortunately, strong AA filters kill fine detail, so manufacturers have a bit of a balancing act in this regard.
What raw converter are you using?

*janosh* · 10-28-2009, 11:24 AM

Originally Posted by Wheatfield

This sounds more like a raw converter problem, although moire can really be a problem with cameras with weaker AA filters. Unfortunately, strong AA filters kill fine detail, so manufacturers have a bit of a balancing act in this regard.
What raw converter are you using?

I convert with Lightroom, do everything there until I get to dodging/burning, which gets moved to Photoshop. What other RAW converter would you suggest?

Right about AA.. Pentax K20D by design does extremely "weak" anti alias filtration in order to get higher detail resolution than one would expect with 14.6MP APS....allows it to rival 5D in most respects...looking at other peoples prints, 5DII seems more vulnurable to moire than 5D AND K20D, but does slightly/visably outresolve both. This would be an argument for film, which doesn't have moire when Nikonscanned....if I emphasized landscape photography.

*Wheatfield* · 10-28-2009, 11:52 AM

Your workflow and mine are pretty much identical. I know that as part of the Lighroom conversion, I find it very easy to oversharpen, so perhaps your culprit is Lightroom itself.
What is your default sharpening in Lightroom?
I find it better to export to Photoshop and do my sharpening there.

*janosh* · 10-28-2009, 01:09 PM

I never sharpen by default in LR...I everything's individual, by eye in the preview...the edge thing comes up with zero sharpening, as if the camera's oversharpening (Pentax doesn't do that does it?)

LR sharpening seems more subtle than PS smart sharpen... Guess I need to go back and study LR vs PS sharpening with the same file. The edge issue comes up only in certain kinds of scenes..almost like it has to do with angle of sunlight...almost like back-lighting, but I don't think that's it.

I get the moire with zero sharpening and have not been able to eliminate it by lowering "Clarity"...which is an interesting tool for portraits of older women.

troyz · 10-28-2009, 08:24 PM

Are you getting the oversharpened appearance immediately upon import, or are you adjusting various things and finding an oversharpened appearance at the end?

Lightroom's parameters can produce some very unintuitive results. You can use the history function in Lightroom to go back to your initial state and then go forward step by step to figure out which adjustment(s) make the problem worse.

Example: a few days ago I had a problem that I thought was a sharpening artifact, but turned out to be caused by the "fill light" function. Go figure.

If the initial import has artifacts you don't like, you could try Pentax Photo Lab or one of the various interpolation options offered by dcraw.

*Canada_Rockies* · 10-28-2009, 10:30 PM

You could download a trial version of DxO Labs software. I only have a K10, but it does magic with it and the DA lenses I own.

*heliphoto* · 10-28-2009, 11:01 PM

Are you using Lr 1.4? and seeing these artifacts on photos which have either been downsized on export from Lr (like reduced for email or web posting)? There is a know fault in 1.4 which to my knowledge they never fixed which caused exactly what you're referring to... 2.5 doesn't seem to do it (I just finally upgraded), but there's an export plugin for Lr called Lr/Mogrify which allows you to use Lr to export the full size image, and then uses imagmagick's tollbox to resize, sharpen and do whatever else you need - Until I upgraded, this plugin was the only way I would export other than full size images from Lr... check it out, it's good.

Google - lightroom 1.4 export artifacts - for more info and to determine if that's what you might be seeing.

*janosh* · 11-03-2009, 07:16 AM

Thanks! Interesting suggestions. I'll go back to the original raw and print without post-processing (no sharpening or anything else in LR or PS) just to see what's up.

I do use the "Fill" quite a bit...it's great with contrasty lighting and I'm seeing the edge issue with distant desert views of mountains...that especially calls for some study. I may have used Fill to find detail, rather than letting those mountains be mere silhouettes

I'm using LR 2.5

DXO relates to lens issues mostly...right? This isn't a lens issue.

Any thoughts about moire? Does DXO address that? My understanding is that it's an inherent problem with Pentax K10/K20 sensor, a tradeoff that leads to higher detail resolution.

*Canada_Rockies* · 11-03-2009, 10:03 AM

Originally Posted by janosh

I'm using LR 2.5

DXO relates to lens issues mostly...right? This isn't a lens issue.

Any thoughts about moire? Does DXO address that? My understanding is that it's an inherent problem with Pentax K10/K20 sensor, a tradeoff that leads to higher detail resolution.

DxO works with the both lens and sensor. It actually makes subtle changes to images taken with my M lenses based on DxO lab's analysis of the k10's sensor.