max49
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f stop blur
Read an interesting article by Craig Tanner on the Mindful Eye site in which he claims that using any smaller than f13 in pursuit of depth of field is counter productive due light bounce inside the lens degrading image sharpness. I have done testing on this and am convinced this is the case. It is quite obvious by pixel peeping up to 100%.I began pursuing this when taking shots at f32 expecting excellent depth of field but being very disappointed with the final results having an out of focus look.I now go no further than f13 and the output is superb.Has anyone else come across this?
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19/Sep/09, 1:31 am
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Bill Allsopp
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Re: f stop blur
I have certainly heard of it.
I stay away from small apertures because it leave me too much work to do removing dust bunnies (although I cleaned my sensor last week - first time in two years - it's a job I dread).
As a landscape photographer I have no need aof small apertures generally, a 17-40 lens will focus from 2 ft to infinity at f 8 ( in theory at least; I give it an extra stop or two usually).
When doing flower pics I have gone as far as f22 occasionally, with good results, and my 180 lens is cracking at f16.
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Bill Allsopp
Don't just look, see!
http://www.britishlandscapephotographs.co.uk
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19/Sep/09, 6:15 am
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crimbo
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Re: f stop blur
http://www.cambridgeincolour.com/tutorials/depth-of-field.htm
http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm
dont think too hard...just take the piccies
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Chris
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http://www.paddle.shetland.co.uk
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19/Sep/09, 7:33 am
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max49
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Re: f stop blur
Hi
Hi Chris thought you would come in on this.Been to Cambridge many times over the years and have learnt much from them.In this case do the test as I have found it to be correct.Dont really want to think to much but do want the best photo I can take and to help everybody on this site which you do so often.Regards Max
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19/Sep/09, 10:25 am
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max49
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Re: f stop blur
Sorry bit of a stuff up there.Found your comments very interesting Bill as the lens in question is a 24-85 canon.Maybe the zoom is the cause.Also tested my 70-200L with the same result.
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19/Sep/09, 10:36 am
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max49
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Re: f stop blur
http://www.tmelive.com/index.php/articles/view/166/22.html
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19/Sep/09, 10:55 am
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Dutyhog
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Re: f stop blur
Hello. Maybe not so much "light bounce", which implies general scattering mistiness or patches, as diffraction. And it could be that your particular lens wasn't designed to be optimum at its smallest apertures, even at its best focal length.
Diffraction becomes significent with all lenses (however perfect) above about f/8 with DX sensors and 10Mpix or so, and gets worse as you stop down, blurring the image detail so that any extra depth of field may not be appreciated because everything gets blurred, wherever it is in the field of view. Try bracketing apertures from eg f/6.3 to f/11 to see if/how much the image quality varies for a particular scene, lens and focal length.
Gordon
PS unfortunately, the Mindful Eye site needs much faster broadband than we can get here.
Last edited by Dutyhog, 19/Sep/09, 11:08 am
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19/Sep/09, 10:58 am
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max49
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Re: f stop blur
Thanks for the reply Dutyhog.Everything you said backs up what I have found to be true.The advice your giving is also I think spot on. Actually I have done exactly the test you suggest except I went further than F11 and found that after F13 image quality dropped off noticeably.For myself I no longer stop down any further than f13 as I have found this to be the optimum.The reason I posted this is to help other members to achieve the best results possible.After many years of photography this came as a complete surprise to me and if it is not right I am hoping the many knowledgeable people here could disprove it.
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19/Sep/09, 1:46 pm
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Bill Allsopp
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Re: f stop blur
A very valid point which many would not appreciate. Thanks.
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Bill Allsopp
Don't just look, see!
http://www.britishlandscapephotographs.co.uk
http://www.billallsopp.co.uk
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19/Sep/09, 2:46 pm
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crimbo
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Re: f stop blur
yes it was a bit of a shock to me coming from film...using the above link if you take a 35mm neg to be about similar to a 24meg sensor then at f22 the image is not diffraction limited...
with my 4/3 sensor it is at f11...
according to the calculator if I set my focus at 0.7m then everything will be 'in focus' down to 0.35m...so what do I need f16 an f22 for?!
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Chris
60N
1W
http://www.paddle.shetland.co.uk
http://www.paddle.shetland.co.uk/my%20piccys/index.htm
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19/Sep/09, 4:01 pm
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