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08-31-2010, 09:13 AM   #31
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There is another option that I don't think anyone mentioned. Were you focussing manually or using auto-focus? AF can easily be off calibration. Once I adjusted my K-x for the FA43 the shots improved like night and day.

Hold on and I'll shoot some tests. Even though it's not the FA31.

08-31-2010, 09:18 AM   #32
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I was actually in a chat with a Pentax rep and he looked at the images. I told him they are unprocessed RAW files and he said even without sharpening applied they look way too soft. He said it is likely front/back focus issue.
Could that be it, given that the worst results happen at infinity? Or is there actual misalignment of the elements inside the lens?
08-31-2010, 09:19 AM   #33
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thanks rparmar, i am looking forward to your samples! I hear the two lens are somewhat similar wide open
08-31-2010, 09:26 AM   #34
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It wold be easy enough to confirm or reject focus issues by shooting a test where you can be sure *something* is in focus. So instead of a vertical subject, one that slants, or one that has a variety of objects in close proximity at slightly different distances. That way, even if you or the camera misses focus on the intended target, something else nearby will still be in optimum focus.

One thing I see here is that your outdoor shots all appear to have been shot in pretty harsh lighting and there are some adverse effects (flare, CA) from that. The crop in the review you linked to doesn't suffer that problem.

08-31-2010, 09:43 AM   #35
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QuoteOriginally posted by oxidized Quote
thanks rparmar, i am looking forward to your samples! I hear the two lens are somewhat similar wide open
If test shots will help, I could take something similar tomorrow and post. My FA31 is MIV, and I can shoot in RAW, open in LR3 and then save as jpeg and post here. May be 100% crops.

But, as I am going to use LR3 with default settings, it may not be directly comparable. But, at least it is a MIV FA31.

In fact after seeing your thread I took a quick handheld shot at f1.8 and did the same as above and they looked sharper than yours.

P.S: I would not call any of my FA limiteds really sharp wide open, but they are certainly sharp enough for the snapshots I may shoot at f1.8 and infinity focus.
08-31-2010, 12:47 PM   #36
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Thanks for the replies guys!

Marc, I understand what you mean. This actually is a good idea. The lighting does matter and there may be something to it. I will try to experiment on a different day or later in the evening. Though, to be honest, in the reviewer's photos it does seem like a mid day photo as well. I will also devise a little experiment (like you said) to see if back/front focus was the problem. How exactly does b/f focus problem work. If I manually focus and I see the object in focus in the viewfinder, could it really be out of focus on the actual picture due to b/f focus?

However, could b/f focus really manifest as such a big problem when at infinity? I mean the depth of field is pretty big even at F1.8 when at infinity. Could that possibly be causing the issue?

Another thing is, as you can see from the shot of the chair arm (i think its either the 3rd or 4th link i posted) i focused right on the begining of the arm and this is the sharpest point. In fact, most of the time I feel like the focus is working fine...

pcarfan, i would really appreciate it if you do that! I am having the hardest time finding something on the internet to compare my shots to!
08-31-2010, 01:33 PM   #37
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QuoteOriginally posted by oxidized Quote
I mean the depth of field is pretty big even at F1.8 when at infinity. Could that possibly be causing the issue?
There is only one plane at which focus is perfect, no matter what the depth of field. For exact testing one should certainly try to fix back-focus (or front-focus) issues. There are standard procedures and test sheets for this, including one by Yvon Bourque.
08-31-2010, 01:35 PM   #38
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I have posted the results of my testing in the thread FA43 sharpness test.

Some conclusions:
1. Manually focus to be sure AF is not the issue.
2. Spot meter to ensure the central area of focus is exposed properly.
3. Use "appropriate" post-processing to evaluate your images. Shots directly out of the camera are sub-optimal and may mislead.

I failed two out of three of these. But the process was informative.

P.S. Despite all this, I do think your lens has a problem.

08-31-2010, 02:02 PM   #39
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QuoteOriginally posted by Ira Quote
and concentrate on getting your in-camera settings right.
I normally shoot RAW, but when shooting thousands of pictures for an event (I get nearly 2x the images with JPEG) or requiring large bursts, I shoot in JPEG.

I try to make my JPEGs like my RAWs for workflow presets, shadow detail, color clipping, and noise.

As a result, I shoot in Natural, with contrast and sharpness set to -4, Shadow Correction at +3, NR off, and saturation at -1 (for some reason this is the only setting I am afraid to go lower on as I feel it might actually desaturate over the original RAW)

Contrast and Shadow Correction are set that way to get the most shadow detail out, similar to RAW. Contrast at -4 had a nearly linear tone curve, according to DPR. Sharpness at -4 because I believe that's actually "no sharpness" as opposed to having a reverse sharpness filter. I always post process contrast manually to get my images to pop. Sharpness is set that way to reduce the amplification of noise with sharpening and to do NR in LR3 or Topaz DeNoise.

The only problem I could foresee is slight loss of precision in contrast steps going from 12-ish bit (less effectively) to 8-bit, but I haven't noticed anything bad.

If I am totally wrong about this, please let me know! Perhaps I should make a new thread.
08-31-2010, 03:43 PM   #40
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QuoteOriginally posted by oxidized Quote
pcarfan, i would really appreciate it if you do that! I am having the hardest time finding something on the internet to compare my shots to!
The shot I took yesterday was still in the folder. If you want something in particular, I could take more tomorrow. Just let me know.

This was taken hand held with center focus point DNG RAW, opened in LR3, made sure the sharpness slider was brought down to zero and then exported as jpeg.

This was taken with the K-7, so a larger image.

Click on the image to go to full res. (well it seems to go to full res. in Mozilla firefox, but not in explorer)

08-31-2010, 03:47 PM   #41
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pcarfan, is the focus on the fence, the back of the house, or...?
08-31-2010, 03:52 PM   #42
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QuoteOriginally posted by deadwolfbones Quote
pcarfan, is the focus on the fence, the back of the house, or...?
I don't recall....I know it was not on the fence, and I used the center focus point and did not move much after focusing, so it is somewhere smack in the middle of the picture.

P.S: I'll do a proper test tomorrow.
08-31-2010, 04:00 PM   #43
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I plan to do one with mine when I get home this evening, too.
08-31-2010, 04:06 PM   #44
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Ok! I just took this. Used the Tripod, 2-sec timer, and center focus point (so, right in the middle of the photo). This probably looks even softer, but the light is very different being very late in the day.

Click on the image to enlarge

08-31-2010, 04:21 PM   #45
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QuoteOriginally posted by deadwolfbones Quote
Is the brick wall test the best for decentering?
Not really. Brick walls are not a consistent surface and often are neither true nor flat. A better test is a standardized lens test target or if that is not available, the poor man's equivalent:
  • Want-ad section from the newspaper
  • Glued flat on a piece of smooth board
  • Photographed at a distance 20x the focal length
  • Care taken to make sure that the lens axis is perpendicular to the target plane
  • Care taken to make sure that the lens is critically focused
At wider apertures, centering defect will show as an obvious asymmetrical lack of sharpness.


Steve
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