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How to select the sharpest aperture ?

Maurice Orozco , Feb 01, 2010; 08:28 p.m.

Hi guys, and thank you so much in advance for whatever help you can share with me. Sorry for the silly question, but I am confuse about this and I would like that somebody clear it up for me and plain explain the formula / technique or steps to follow to select the sharpest aperture. Maybe this is not relevant but I do have a D300 ( Nikon 16-85 mm and 70-300 mm VR ). I have made some investigation about this and there are some formulas to apply to select the sharpest aperture. Is there any simple way to find out which aperture is the sharpest without having to apply math to get the result ? I am not bad at math, I am just simply saying that there should be a quickest way to do this so if anybody would like to share that info with me, please do it and I will really appreciate it. Sorry again to ask this silly question but I am inclined to details and exact and clear information. I know that I have to focus on the farthest thing I want sharp and then on the closest thing I do want sharp but how do I calculate the distance for both to finally calculate the sharpest aperture ? Do you need to be in A mode or M ? How close to the closest thing you need to be to apply this ? Where do you need to focus ? 1/3 ahead or 1/2 ahead of the closest thing ? Sorry again to bother you with this question but I am not a pro but I am looking forward to be close to it some day. Can you help guys ?
Thank you so much again for all of your help and please forgive me for this silly question !!


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Avery Pickford , Feb 01, 2010; 08:43 p.m.

What do you mean by sharpest? f/22 will have more of the picture in focus. So ignoring everything else, I suppose if this is what you care about you should always shoot at f/22.
In reality, you shouldn't ignore everything else.
You may WANT part of the photograph to be out of focus.
You'll run into other issues w/ using lenses at f/22 (which will depend on the lens).
And the big one...usually you don't have enough light to shoot at f/22 and still have a reasonable shutter speed.

Or maybe this isn't what you meant at all...

Mark S , Feb 01, 2010; 08:59 p.m.

Maurice, photography is not all about mathematics and formulas. There is an artistic quality that is really fun to explore.
I would recommend you go out and experiment. See what looks good to YOU.
I don't think its really possible to apply a formula for what you are looking to achieve, as there are just way too many variables in composing each individual photograph.
Got experiment and have fun.

Bjorn Rorslett , Feb 01, 2010; 09:02 p.m.

There is no "formula" for this. A rule-of-thumb is that pro-grade lenses, in particular long ones, are performing at their best 1 or 2 stops down from the maximum. For fast f/2-f/2.8 lenses that could mean f/2.8 or f/4 is in the peak region. For wide-angle zoom lenses you might have to go to f/8-f/11 to get peak sharpness. Test your lenses and you'll find this out for yourself, with your own gear.

If you plan on shooting at f/22 all the time the above is moot because most of the available sharpness is wasted on getting a deeper depth-of.field, which might not even serve the photo the best. Learn how to use the aperture to get the final result you wish to have.

The 1/3 in front, 2/3 i the back rule is one of the many myths floating around in photographers' circles. Just forget it. Focus on what's most important in the picture.

Arthur Yeo , Feb 01, 2010; 09:43 p.m.

If by the sharpest aperture, you mean to say the highest resolution, then for most lenses, it is most likely about 2-3 stops above the widest aperture.

So, for a 50mm/1.4 lens, the peak tends to be around f/4 - f/8 and then, the resolution fades beyond that because of diffraction.

Maurice Orozco , Feb 01, 2010; 10:10 p.m.

Ok guys, thanks a lot for your help. Bjorn, I will apply what you told me and most of all, I will try not to be too technical. Mark you are right about being artistic.

barry goldberg , Feb 01, 2010; 10:48 p.m.

There's a great book that delves into this and I strongly recommend it. It is Understanding Aperture by Bryan Peterson.

Gary Demuelenare , Feb 01, 2010; 11:45 p.m.

there is no formula. generally, the sharpest image in somewhere in the f5.6-f11.0 range. the actual sharpest fstop is also in that range. the only real way to find out is to let a lab test the lens.
if you recall the old saying "f8.0 and be there". there was a very good reason why f8 was used. that is generally going to be very close the sharpest aperture. personally, i just use f8.0 and do not worry about it.
also, there is the matter of difraction distorsion. this is what happens to light when it poasses through a small hole. it diffracts or distorts. for c sensor dslrs this means diffraction is beginning at any fstop beyond f11.0. yes you get a lot of dof at f16-22 but it is at the price of the diffraction. whether the dof is worth it is up to you. for me, i try not to shoot at any fstop beyond f11.0. higher fstop really are no t needed anyway if a dof table is used.

Luis G , Feb 02, 2010; 01:10 a.m.

Maurice, it's not a question of formulas, or the usual 2-stop above wide open thing, though it's likely right. It is a question of you becoming intimately familiar with your very own equipment and learning to do your own testing and analysis of images.

Matthew Currie , Feb 02, 2010; 01:11 a.m.

If you're shooting digital and not paying for film, why not put the camera on a tripod, aim it at a complicated subject with some depth, lots of detail, and edges, and try all the apertures on a lens? Skip the math and see for yourself what your own equipment does, what aperture gives you the best sharpness, how much diffraction is actually visible, and how much it matters to you.

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