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Old Apr 22, 2006, 3:22 PM   #1
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Hi all,

I'm still experimenting with my Sigma 170-500. I'm struggling rather with sharpness, especially at the long end, and am trying to work out whether it's technique, inaccurate focusing, sharpness drop-off due to being at the long end, and/or drop-off due to the slower shutter speeds (smaller apertures) at the long end.

Anyhow, this is the best from today's efforts, taken at around 250mm, spot metering, hand on top of the lens to damp vibrations (trying to learn the proper techniques).

Not sure about the composition on this... does it have any appeal? What would you have done differently?

Regarding the sharpness issues:

I've noticed that the subjects that are further away from me tend to come out blurrier, and have brought it down to one (or more) of three things:

1: subjects that are further away, mean I'm using the long end of the lens, so therefore it's to do with inherent loss of sharpness

2: the AF (and/or my eye, as I've been using MF sometimes) is worse at that distance, and thus I'm missing the focus.

3: vibrations from the shutter/me are accentuated, the longer the lens gets.

As you can see, I'm going around in circles here... anyone have any advice as to which of these scenarios is the most likely, and/or any advice on what long lens techniques have worked for them?

Best wishes,

-Ben



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Old Apr 22, 2006, 3:48 PM   #2
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i just get a feeling a bit of over Post processing. May be its me or my stupid monitor...

viks
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Old Apr 22, 2006, 4:02 PM   #3
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Hi Viks,

Thanks for the comment - I can see how it looks over PPed. I think in this case it might be the high contrast of the photo - having spot metered on the black crow, the grass is rather blown out on the original. Attached is the original for comparison. It's still more than possible I overdid it on the PP, though!

FYI, PP was: raw conversion (shot in raw+jpg), shadow/highlight tweak, levels edit, sharpening at 120%

Best,

-Ben
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Old Apr 22, 2006, 8:33 PM   #4
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Not a bad shot of a crow at all. Black birds are a pain to get detail with, and you have done a good job of it. I think the slight softness is probably due to shutter speed being a little too close to the limit of the hand shake rule-of-thumb of 1/focal length. Remember, this is for "acceptable' sharpness, and I have come to the conclusion that means "not visibly blurry". If you get another like this, try a quicker exposure and wider aperture and check results.

brian
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Old Apr 23, 2006, 7:23 AM   #5
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Thanks for the comment and suggestion Brian - much appreciated as always. Unfortunately, I neglected to mention that these were all shots taken using a tripod (Slik 700dx), so I don't think the blur's from hand-shake per se, although it may well be from shake of some sort... Still, I agree, shooting with quicker exposures and wider apertures certainly can't hurt, light depending; I'll give that a go next time.

Maybe I'm expecting too much of my kit? - since I got a tamron 90mm macro a while back, I've been comparing everything for sharpness to it. My two long lenses just never seem to have anywhere near that sharp - especially at their long-ends. Any input on what sort of sharpness i should be expecting from my long lenses would be appreciated...

(Sigma 170-500, and Minolta 75-300 (old metal 'beercan' version).

Best,

-Ben
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Old Apr 23, 2006, 9:23 PM   #6
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If you can do comparison shots of same subject, it will give you a better idea of lens or camera. I began noticing my old Series 1 70-210 on my SRT wasn't giving me the sharpness it used to, and by shining a laser pointer throgh it, found a film building up on the interior lens elements. Still does OK for portraits where I want soft, though.

brian
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Old Apr 24, 2006, 12:08 PM   #7
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All's been said. Great capture.
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Old Apr 24, 2006, 2:33 PM   #8
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thanks for the comments Viks, Brian, Syd - much appreciated.

Brian - thanks for the advice - I'll check my lenses out that with a laser pointed, and also try to do a comparison.

Best,

-Ben
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Old Apr 24, 2006, 3:34 PM   #9
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Hi,

Well I posted a shot of a bird up here at 300mm and it was nowhere near as clear and sharp as your shot posted. I think if this is one of your problem shots then you don't appear to be doing too much wrong!

However look forward to seeing birds in motion - i found this a lot harder!

Dom
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Old Apr 24, 2006, 5:40 PM   #10
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In my opinion Ben this is a great shot. I've spent thewinter trying to get as good of a detailed shot of black Grackles. Black birds are very hard to shoot. Nice work!
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