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Post by tonyg14 on Apr 22, 2008 6:16:05 GMT
Dear Romy,
How do you test for sharpness re: Canon 100-400mm L at wide open where it is going to be for bif shots.
Saw a brand new one but not too confident about my ability to test for sharpness.
Tonyg14
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Post by Romy Ocon on Apr 23, 2008 11:21:40 GMT
Hi Tony,
I'm out of town right now and accessing our forums via snail-slow GPRS (no 3G signal around), I'll answer your post in detail when I get back to the city.
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Post by Romy Ocon on Apr 24, 2008 13:40:55 GMT
Hi Tony,
When buying lenses, I test two things:
1. AF calibration with my main DSLR. I set up three AA batteries diagonally to me, and shoot the middle one, using AF, at full zoom, wide open and just beyond the minimum focus distance (to come up with the thinnest DOF for the lens). The middle battery should be sharp, otherwise there's a back/front focus issue.
2. Most copies of the 100-400 are sharp at full zoom and f/8. Good copies are sharp at 400 mm even at f/5.6. A quick check if a 100-400 is a good copy is to shoot a detailed subject at f/5.6 and f/8. If the sharpness is similar, then the lens is good.
Romy
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Post by Reyno Rosete on Apr 24, 2008 19:42:08 GMT
Why batteries, I normally do the "beer can test" but I don't drink the contents until I'm done with testing !!!
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Post by Ed Matuod on Apr 25, 2008 2:56:46 GMT
Reyno, try fundador. I like the color combination. Besides sharpness test, you can test color cast too. Am right, Romy?
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Post by tonyg14 on Apr 25, 2008 7:05:52 GMT
Guys, Thanks.  |
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Post by tonyg14 on May 7, 2008 2:14:22 GMT
Romy, I was allowed to test the camera. Based on the test parameters you gave at wide open the 100-400 appears to be sharp. I took some shots of a painting and some stuff toys and I found the lens sharp f/ 5.6 at wide open and a little soft at f/8. The battery test.  f/5.6, 400mm  f/5.6,400mm, 1/100  f/8, 400mm, 1/40  f/8, 400mm, 1/25  f/5.6, 400, 1/40 Tony |
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Post by mantarey on May 7, 2008 2:50:45 GMT
That's strange. F8 should be sharper than 5.6.  |
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Post by Ed Matuod on May 7, 2008 3:34:36 GMT
For mine, the sweet spot is @ 350mm and below and aperture @ -2 or -3 stops wide open.
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Post by tonyg14 on May 7, 2008 5:00:47 GMT
Rey,
I showed the photos to Bong and he pointed out what I saw last night that at f/8 wide open the shots were soft. I was surprised myself.
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Post by Romy Ocon on May 7, 2008 7:53:41 GMT
AF looks great! As regards sharpness, we need to see 100% crops.
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Post by Martin Alvendia on May 7, 2008 12:39:46 GMT
Could it be the shutter speed at f/8 was at 1/25, as such being more induced to camera shake?
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Post by Mark Itol on May 7, 2008 13:55:14 GMT
I agree with Martin with regards to the camera shake (assuming you took the shots handheld), as most (if not all) lenses are sharper a stop or two from the maximum aperture. |
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Post by tonyg14 on May 7, 2008 14:06:28 GMT
Martin and Mark, s
Possible since handheld.
Tony
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