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06-27-2013, 02:40 PM   #1
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DAL 55-300 Auto focus check

Not sure if this is the correct forum. Still pretty new at all this and without background, devised a simple and hopefully valid check on my new DAL 55-300. The photos are of a 5" x 5" box, taken with my K-01 on a tripod and using shutter timer. I would like to know if the detail is adequate for the circumstances. I had taken photos at 300mm, 200mm, 100mm and 55mm, and then cropped them to only the object in question. Snaps were taken from about ten feet away in the crummy lighting of my workplace, using center focus.


Input on the test results, or how better to test are kindly welcome.

Thank you in advance

Banskojoe

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06-27-2013, 03:55 PM   #2
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Hi, welcome! This might not be the right forum, maybe the mods will move it, but here is my opinion anyway.
For hand held in dark light with high ISO that might be expected results, but with a tripod and 2 sec timer, the results should be better.
Here are two tips:
Put the box at an angle to the lens, so you can see if the focus hit anywhere near or not at all.
And then use a nice heavy tripod, Av mode with ISO 100 and the aperture that you want (probably one stop above wide open)
06-27-2013, 04:01 PM   #3
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QuoteOriginally posted by Na Horuk Quote
Hi, welcome! This might not be the right forum, maybe the mods will move it, but here is my opinion anyway.
For hand held in dark light with high ISO that might be expected results, but with a tripod and 2 sec timer, the results should be better.
Here are two tips:
Put the box at an angle to the lens, so you can see if the focus hit anywhere near or not at all.
And then use a nice heavy tripod, Av mode with ISO 100 and the aperture that you want (probably one stop above wide open)
Thank you (Hvala?) More experiments to come!
06-27-2013, 04:15 PM   #4
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lol yep, Hvala is the correct word
Btw, you can also take a photo with AF and then a second photo with manual focus (maybe with focus peaking). And list your AF mode, some AF mods on the K-01 are not very good (you probably want to choose select point AF, where you can move the square around and change its size and the camera will try to maximize contrast in that square)

06-27-2013, 04:18 PM   #5
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You are on the right track. It might be better to use a more contrasty subject such as a page of fine print newspaper stuck to a convenient wall. Make sure that the camera is set up with the lens axis perpendicular to this in both the horizontal and vertical planes. If you are just trying to evaluate the lens then use manual focus in expanded liveview, otherwise your method should be fine. Try to keep the distance at least 50x the focal length. Don't worry too much about illumination - as long as it is uniform, since if you have the camera on a good tripod you can use longish exposures, but stick to low ISO. Take shots at different apertures and preferably shoot RAW files. Then load the files into your favourite post-processing software, pixel-peep before and after any processing that you would normally make, such as distortion, CA correction or sharpening. Uncorrected CA can make a lot of difference to perceived sharpness, Look at the frame corners (these should be all equally bad or good) and compare to the frame centre.

Things to look for are any obvious signs of lens decentering (that's why the alignment of your camera to the target is important) etc. Shooting at different apertures will give you some idea of the lens 'sweet spot' aperture at each focal length. Don't get too worried if the lens does not seem absolutely pin sharp in the corners at wide apertures - go out and take some real pictures

This was my quick test on the 55-300 when I got it, on a K-7.
06-27-2013, 04:32 PM   #6
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Little stange to check the focus on the K-01.

K-01 uses contrast AF and it use the actual sensor so that means you don't have front or back focus problems like you have with phase AF
06-27-2013, 09:40 PM   #7
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QuoteOriginally posted by Anvh Quote
Little stange to check the focus on the K-01. K-01 uses contrast AF and it use the actual sensor so that means you don't have front or back focus problems like you have with phase AF
+1 the test as conducted is fine to see the results of the lens IQ or to check for element alignment or decentering. But as Anvh points out the k-01 uses CDAF and there is no AF adjustment.
06-28-2013, 02:37 AM   #8
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There is no AF adjustment needed to be 100% correct.

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