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05-06-2008, 04:26 AM   #1
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Resolution Tests

See post #16 for my offer to send you any of the high resolution files for any of the lenses I've finished.


Last edited by YarPcola; 05-07-2008 at 10:29 AM. Reason: Technical problems
05-06-2008, 04:37 AM   #2
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Okay, I just realized that the Flickr files don't do justice to the resolution tests. I guess they compressed the files too much. Therefore, don't waste your time, (at this time). I'll try to figure out how to show higher resolution files, or just close-ups of the targets and hope that gives more accurate results. Suggestions anyone?
(Is there a way to delete this thread?)

Last edited by YarPcola; 05-06-2008 at 04:52 AM.
05-06-2008, 07:01 AM   #3
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Hi, yes, resolution tests need to be at 100%. If Flickr reduces size to 1024px, you must crop to that or a smaller fraction in the first place -- or use another provider.

Last edited by falconeye; 05-06-2008 at 11:17 AM. Reason: shortening after delete
05-06-2008, 08:54 AM   #4
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FWIW, you can post whatever size you want at flickr... once its posted, you click on 'All Sizes' above the image and choose the link to the size you like located under the photo.

05-06-2008, 11:22 AM   #5
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QuoteOriginally posted by thePiRaTE!! Quote
FWIW, you can post whatever size you want at flickr... once its posted, you click on 'All Sizes' above the image and choose the link to the size you like located under the photo.
The free account is limited to 10MB/photo & 100MB/month. This is just sufficient for 10 K20D full quality JPEGs if one carefully controls their size stays <10MB.

The pro account is still limited to 20MB/photo (which is ok for K20D).
05-06-2008, 11:53 AM   #6
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Even at the largest Flickr size the resolution tests showed an entire row of targets as blurred that were clear in the pictures I sent in. When I saved a sample Flickr picture, (again at the largest size), it was considerably smaller (and more blurry) than the original.
05-06-2008, 12:13 PM   #7
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I think I found a solution. I just cut and paste a center resolution chart and corner resolution chart for each of the tested f-stops into a new document. There were a total of seven charts on the target, but all four corners look pretty much the same and the edge charts are also a bit too much. This way I can get a center and corner resolution chart for all f-stops onto a single document.
Like this:
Attached Images
 
05-06-2008, 12:18 PM   #8
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By the way, don't try to judge too much from the above picture. My file was 443K but it downloaded to 61K. Again, an entire row of resolution is blurred which show up in the original - much like what happened with Flickr. I checked with the original pictures and the 443k size captures all the resolution necessary to read the charts.


Last edited by YarPcola; 05-06-2008 at 12:21 PM. Reason: Addition
05-06-2008, 12:25 PM   #9
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This is what the original target looked like:
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05-06-2008, 12:54 PM   #10
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Okay, I just had a rather rude realization. For the first time I really studied the 90 shots of the 11 tested lenses and guess what? At 10 megapixels and with three star quality, there isn't enough difference to matter! Except for a very few really bad settings, like wide open with some of them, they all resolved the same! I guess I should have shot in RAW. Oh well, two days work for naught. But I guess the knowledge that when shooting a JPG your lens doesn't really matter (as far as resolution is concerned), is worth something.

(And yes, I used the two second delay and a heavy tripod, a SLIK Pro 700DX.)

Last edited by YarPcola; 05-06-2008 at 01:00 PM.
05-06-2008, 01:54 PM   #11
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QuoteOriginally posted by YarPcola Quote
there isn't enough difference to matter!
Oh no, all the work! The 50mm shot fully open looked fuzzier, BTW, even in the forum's download.


I once did domething similiar, but with only 3 lenses and 2 apertures. I knew I had 2 *** and 1 **** lens. Still couldn't see it in test shots. In my normal photography, though, I always see the difference, immediately.

It probably is a contrast thing. On black/white test charts the contrast may be that high that it always comes out nicely.

A Siemens star
\|/
-*-
/|\
may be more telling, as at some point in the inner part you stop to see the lines. If you see Moire in the middle, you know that the lens outperformed the camera.

Of course, correct focus and RAW processing may be necessary as well. Just my 2 cents, if you want to look into this again.
05-06-2008, 02:17 PM   #12
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Heya YarPcola, without getting too far into it, JPEGs are a compressed format. Depending on the dithering algorhythm used (the pattern the computer uses to remove bits from the larger image to create the smaller file), the final appearance can appear close to or much worse than the original sharpness but in all cases, the depth of the detail is lost to compression. Once you are looking at a JPEG, you are looking at the programs interpretation of the sharpness of your lens test, rather than the RAW output.

I have messed with a few programs for creating viewable versions of my large work, but even having done that (I really like Lightroom and Irfanview btw for JPEG conversion) All the finite detail in lost, hence the use of 100% crops. In my experience, I haven't had the problems you have mentioned while using Flickr though - I post all my lens test there and the resulting images are exactly the same as the JPEGs I created.

If you already know all this, sorry for the rambling, heh.
05-06-2008, 03:40 PM   #13
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QuoteOriginally posted by thePiRaTE!! Quote
JPEGs are a compressed format. Depending on the dithering algorhythm used [...] the depth of the detail is lost to compression. [...] All the finite detail in lost, hence the use of 100% crops.
I'm not sure, but you may have a misperception about what JPEG is.

First, JPEG doesn't use any sort of dithering.

Second, JPEG doesn't resize an image -- many people confuse the fact that, e.g., Lightroom resizes in its export to JPEG, the resize with the compression. One has nothing to do with the other.

Third, JPEG in its highest quality setting, doesn't produce a visible loss of detail. It is just not recommended to store intermediate version in JPEG because of little headroom for further processing and the loss by subsequent load/stores.



With the K10D, the problem is different: Its JPEG engine (the compression code) is bad. Fixed with the K20D.
05-06-2008, 05:31 PM   #14
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QuoteOriginally posted by YarPcola Quote
Okay, I just had a rather rude realization. For the first time I really studied the 90 shots of the 11 tested lenses and guess what? At 10 megapixels and with three star quality, there isn't enough difference to matter! Except for a very few really bad settings, like wide open with some of them, they all resolved the same! I guess I should have shot in RAW. Oh well, two days work for naught. But I guess the knowledge that when shooting a JPG your lens doesn't really matter (as far as resolution is concerned), is worth something.
I've gotta disagree. I was able to quite easily detail resolution differences in lenses with my K100D in three star JPEG. Even the nearly imperceptable difference between an A 50 1.7 and 2.0 was discernable (surprisingly, the f/2.0 photos were slightly better - manual focus DAO error difference perhaps?). The new and improved AL II kit lens set to 50mm was dramatically different.

What camera are you using? Have you tried kicking the sharpness setting up one notch?
05-06-2008, 05:34 PM   #15
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You're right Falconeye, I have my terms fouled. I have a habit of learning only what I need to know to solve my immediate problems and fill in the blanks later - well, now is that time for my JPEG terminology.

I think my description still gets the right idea across, though 'dithering' should have read 'quantization'. I understood what the JPEG was doing to the file, but not expressly how (until now). And thanks for mentioning, I get ahead of myself sometimes, I'm glad to learn.
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