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01-25-2009, 06:28 AM   #16
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Well, here are my results for the focus chart test.

I tested the lens always wide open (f2.8) and using a tripod.

50mm






63mm






75mm






95mm







135mm




As you can see, it seems obvious that it performs quite badly at 50mm and as I zoom in getting closer to 135mm the back focus problem almost dissapear. Also, I noticed that left side of the chart is more blurry than the right side, so it may have another problem with internal lenses, am I wrong??

Waiting for your opinion. How should I proceed now?

Thanks a lot.

01-25-2009, 06:30 AM   #17
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By the way... I did the test with my Sigma 70mm Macro and it performs almost perfect... no BF problems.
01-25-2009, 06:52 AM   #18
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Test Chart site?

I just tried to go to the limk provided by Marc ( focustestchart.com ) and got a page that said that the web page has expired. (Sunday, Jan. 25, 2008, 8:50AM New York Time, US Eastern Standard Time). Is there another site somewhere?
01-25-2009, 07:26 AM   #19
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Hi I would definitely try to use the debug mode first before you send your camera for repair. I bought an FA 35 F2 and it backfocused also quite like yours. As some others said in this thread inconsistent backfocusing ,may not mean your camera lens combo backfocuses or it may also simply mean it backfocuses. Backfocusing can happen 7 times out of 10, if playing around with the debug menu improves it by 3 times out of 10 then I would certainly say it would be worth it.

My suggestion is aside from checking (after correction in the debug menu) using a focus test chart try shooting real subjects (in my case I used flowers) at a focus distance you plan to use the lens most often, shoot wide open and apply correction at that distance.

In my case It was was easier since the lens was a fixed focal. In your case you may have to shoot at different focal lengths and get a compromise where you get the sharpest image most of the time at all focal lengths. Also shoot at slower apertures afterward (5.6 and lower) to see if that was affected by the adjustment.

These are 100 % crop test shots before and after the focus adjustment using the K10D debug mode. I chose a little short of 3 meters as my focus distance from the subject. At this distance the lens/camera was consistently focusing on the green drapes to the back of the flowers.

The second shot was after focus correction. Surprisingly after I did this there was no affect on my other lenses and in fact they all seem to have improved in focus as well.





01-25-2009, 11:04 AM   #20
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QuoteOriginally posted by cooldude14es Quote
Well, here are my results for the focus chart test.
Are those crops? They don't appear to be centered at all, plus they aren't very straight, nor do they appear to be shot at anything close to a 45 degree angle. Can't conclude anything from these.

Looks like the domain has indeed expired. There are probably other sites with copies of this chart, and there are other charts too. The idea is to give the camera soemthing to focus on that it can't possibly miss, and the provide a scale - nowhere near the target or it might focus on the scale instead of the target - to show where the focus is.
01-25-2009, 11:35 AM   #21
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the only way to do it properly is at the angle. 45 degrees or more. Otherwise it's not accurate
01-25-2009, 12:24 PM   #22
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Here there is the pdf file:

Download Focus Test Chart - Digital Camera Reviews & Photography Tips

Probably I did some mistakes but it was 45 degrees for sure, I will print the chart again and do the test once more ...

I dont know how to do it at 50mm because minimum focusing distance on this lens is 1m. (40 inches) and then one can not fill the frame with the chart only...
01-25-2009, 01:53 PM   #23
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QuoteOriginally posted by cooldude14es Quote
Thanks. This time I downloaded it and saved it. It's not the same chart I originally used, but it is functionally the same thing.

01-25-2009, 11:40 PM   #24
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QuoteOriginally posted by cooldude14es Quote
Probably I did some mistakes but it was 45 degrees for sure
If it was 45 degrees, the bottom half of the chart would be significantly closer to you than the back and hence look much bigger. I don't see that happening at all. Plus as I said it's not even close to being centered or straight. The focus target needs to be dead center. The vertical lines on the chart should be angling upward and inward at exactly the same angle (but in opposite directions, of course). As it is, they are barely angling at all, but the lines on the left side is angling in far more than the right.

QuoteQuote:
I dont know how to do it at 50mm because minimum focusing distance on this lens is 1m. (40 inches) and then one can not fill the frame with the chart only...
Just do it from as close as you can. The important thing is to center the target and have the chart completely straight, while shooting at an angle from above. It looks to me like you did *none* of these things.
01-26-2009, 07:11 AM   #25
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debug mode

QuoteOriginally posted by azcavalier Quote
Debug mode can only be activated if you haven't upgraded your K10D to the latest firmware.

Also, I should add that one of the nice things about the K20D is that the ability to tweak the focus is included in the setup menu...without having to enter debug mode.
if you have the 1.0 firmware then you can update it to 1.1 and access debug mode.
01-26-2009, 07:52 AM   #26
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re:

QuoteQuote:
If it was 45 degrees, the bottom half of the chart would be significantly closer to you than the back and hence look much bigger. I don't see that happening at all. Plus as I said it's not even close to being centered or straight. The focus target needs to be dead center. The vertical lines on the chart should be angling upward and inward at exactly the same angle (but in opposite directions, of course). As it is, they are barely angling at all, but the lines on the left side is angling in far more than the right.
Seems the paper wasnt completely flat when he took the shot so even if the camera was 45 degrees the angle of the paper might haved messed the shot.
01-26-2009, 11:33 AM   #27
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Ok, I hope this one is better for checking results. All pictures are cropped to show better the center point:



50mm






63mm







75mm







95mm







135mm





Two things I noticed: left side is a little more blurry than right side, and it took me quite long to take a centered picture since it seemed when everything was straight the picture was not, like if the lens or sensor was bad aligned...

Sorry about my english, it is hard to express an idea in another language

Waiting for your feedback. Greetings.
01-26-2009, 12:42 PM   #28
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QuoteOriginally posted by cooldude14es Quote
Ok, I hope this one is better for checking results
Much! And I think you'll agree they don't show any particular BF or FF problem... which doesn't surprise me since you said what you were seeing was intermittent.

QuoteQuote:
Two things I noticed: left side is a little more blurry than right side
I can't say that I see that, although maybe it's more noticeable at 100%. I'd say some of the shots are still *slightly* tilted to the right, so the actual zone of acceptable focus is a little shifted forward on the right side compared to the left. But the corresponding areas of both sides look similar to me at the size posted.

QuoteQuote:
it took me quite long to take a centered picture since it seemed when everything was straight the picture was not, like if the lens or sensor was bad aligned...
Or the viewfinder. I suppose another test using a tripod, a brick wall, and lining up the lines on the wall with the lines etched into the focus screen might be worthwhile.

QuoteQuote:
Sorry about my english, it is hard to express an idea in another language
Actually, you're doing well enough that I wouldn't have guessed.
01-27-2009, 01:37 AM   #29
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Thanks Marc, your help is much appreciated.

Then, maybe the problem was on the user (me!!), although I still think there is a little BF at 50mm, but I suppose not too much to worry about.

I will do the brick wall test, because it may be another problem within the viewfinder, and I will also do some more walking around photos to see how the focus acts at 50mm in real life.

Thanks a lot.
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