armandtchou wrote in post #14037621
Thanks for your opinion.
I'm indeed very happy with my 55-250 too.
Thank you for these examples! Yours seems great. I tried again my "chinese map test" with a LED spot, lightning is now a bit better. These links show my results:Example 1 :
55-250, 55mm, f/5.6, 1/15Example 2 :
15-85, 57mm, f/5.6, 1/15
I know I'm not in the best focal range of my 15-85 but on these two pictures it is definitively softer in the center of the frame than my 55-250. It's very clear on the pink border between China and other countries. It seems to be a bit better in corners.
I also noticed that I always had to focus twice with the 15-85 to obtain a sharp image. The first try is always blurred.
It confirms an impression I had when I took train pictures you can see in one of my previous message. That has never happened with my 17-85
I'm taking a look at them now, first the 55-250 (it definitely gets a lot sharper with good light ). The second thing I noticed, after downloading them and viewing in Photoshop at 100% view, is that the map in the 15-85 image is smaller than the map in the 55-250 image (I assume you shot them from different distances, since the overall image is different between the two lenses); it will be more difficult to compare if they're not exactly the same framing. That being said, they both look pretty sharp, although the 15-85 may be a little softer, which I would not expect between these two lenses. I hope it will be OK if I post a 100% side-by-side comparison from both images (although again, they're difficult to compare because the map is sized differently in the two images) - please go to your User CP and click to allow editing your images. I'm posting this since it's a technical question, and hope that will be all right with you. These crops are from the approximate center of the map, 55-250 on the left and 15-85 on the right.
It may be time for you to try some more basic tests, such as the battery shot test. Take three to five AA size batteries and line them up, then shoot them at a 45 degree angle to the line of batteries, focusing on the center battery. Make sure they're far enough apart when viewed at 45 degrees so that the focus square will only cover the center battery. Use the widest aperture your lens allows at whatever focal length you choose (e.g., f/3.5 at 15mm for the 15-85, f/5.6 at 85mm). If the center battery is sharply in focus then your lens is probably working properly. If the center battery is out-of-focus and one of the other batteries is in focus your lens is probably front- or back-focusing (if the in-focus battery is closer to the camera than the center battery it's front-focusing; if the in-focus battery is farther from the camera than the center battery it's back-focusing).
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