Archive 2008 · help on sharpness

padang
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p.1 #1 · p.1 #1 · help on sharpness

Hi,

Hi !

I have 8 similar shots done in same conditions:
- triopd
- 50mm USM 1.4
- ISO 100
- 1/100 shutter speed
- f/2.5: I know it is probably too opened for a portrait, but here my goal was to test accuracy of focus

Just one of them is sharp, a low success rate.

Do you have some theory about what may be wrong: focus ? unstable tripod ? moving subject ? Too high expectations ?

Here is a 100% crop of the sharp one (with focus area as shown by ZoomBrowser, no recomposition):
http://farm4.static.flickr.com/3054/2806428074_f3417a7ecb_o.jpg
full image

All the 7 others are like this one:
http://farm4.static.flickr.com/3150/2805578601_11bc847130_o.jpg
full image

These photos were taken with Canon XSi. Tried also with 40D, but not much better: (best crop over a set of ~10 too)

http://farm4.static.flickr.com/3043/2806461900_248c650c4d_o.jpg
full image

Thanks a lot for your help :-)

Note: if I do some controlled focus test with batteries, everything seems good.

Edited on Aug 28, 2008 at 04:36 PM

Aug 28, 2008 at 04:32 PM

Scott Stoness
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p.1 #2 · p.1 #2 · help on sharpness

Theory 1: f2.5 at 6 feet 50mm will have depth of +-.2' or +-3". If you press your shutter it focuses and then he moves, then he is out of focus. Try this with an adult. Even a rotation of his head will blur. And +-3" is an acceptable focus which will not look good if you pixel peep as you are doing above. So a delay in pressing all the way down the shutter, while he moves out of focus could cause this.

Theory 2: 1/100 is a the bottom end of fast for motion. If he moved it would be blurred. Move up to 1/200 or better for safety sake.

Theory 3: If the camera automatically selects the focus point and you shoot it will be focussed on his shirt when you want it focussed on his eye. I always use centre focus and shift to shoot for this reason.

Theory 4: All raw shots require sharpening. You have not sharpened.

Theory 5: All all of the above.

Edited on Aug 28, 2008 at 06:44 PM

Aug 28, 2008 at 06:42 PM

Genes Home
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p.1 #3 · p.1 #3 · help on sharpness

Kick ISO up to 800 and reshoot with everything else the same, but faster shutter speed.

I agree with Scott that you were setting up a focus failure situation.

an additional item, how are you releasing the shutter? anything other than a timer or electronic remote (wired or wireless) will add some camera movement which may be an issue when you are working so close to the edge like this.

Aug 28, 2008 at 06:55 PM

padang
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p.1 #4 · p.1 #4 · help on sharpness

Thanks a lot for looking into that !

Scott Stoness wrote:
Theory 1: f2.5 at 6 feet 50mm will have depth of +-.2' or +-3". If you press your shutter it focuses and then he moves, then he is out of focus. Try this with an adult. Even a rotation of his head will blur. And +-3" is an acceptable focus which will not look good if you pixel peep as you are doing above. So a delay in pressing all the way down the shutter, while he moves out of focus could cause this.

ok, good one. Let me try again.

Theory 2: 1/100 is a the bottom end of fast for motion. If he moved it would be blurred. Move up to 1/200 or better for safety sake.

he was still.

Theory 3: If the camera automatically selects the focus point and you shoot it will be focussed on his shirt when you want it focussed on his eye. I always use centre focus and shift to shoot for this reason.

nope.. I was center focus (hence the bad composition :-D )

Theory 4: All raw shots require sharpening. You have not sharpened.

nope.. one is good, the other bad - same out-of-the-box settings.

Aug 29, 2008 at 01:38 AM

padang
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p.1 #5 · p.1 #5 · help on sharpness

Genes Home wrote:
Kick ISO up to 800 and reshoot with everything else the same, but faster shutter speed.

I made several attempts, and anything above ISO200 creates too much noise to get the eyelashes sharp. Results seem better if I open-up the lens, but I understand the tradeoff.

anything other than a timer or electronic remote (wired or wireless) will add some camera movement which may be an issue when you are working so close to the edge like this.
I was using 2s delay with mirror lockup, but it could have created theory #1 above..

BTW, IS is doing some magic... Here is a handheld 100% crop at 1/10s with my 17-85 IS at 50mm:
http://farm4.static.flickr.com/3262/2807199949_0997a36a15_o.jpg

And the same at 1/125s with tripod:
http://farm4.static.flickr.com/3105/2807199897_125b4d30b6_o.jpg

Do you see any difference ? Seems the same to me ! I'll ditch the tripod I think.

Edited on Aug 29, 2008 at 01:45 AM

Aug 29, 2008 at 01:42 AM


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