Lens sweet spot?

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Ciaran
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#1
Not sure if this the correct forum, but maybe some of you more experienced people can answer this...
Its been said that there are sweet spots on lenses with regards to the aperture (I believe its better towards the mid range?)
In these areas, is it only the sharpness that is better, or does it improve the colours captured etc as well?
 
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Trevor
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#2
Just the sharpening and any distortion really, colour shouldn't be affected.

It's less of a problem on crop sensor cameras as they don't use all the lens, but generally cheaper lenses aren't as good wide open. If you stop down to f8 or so it can improve things.

To test your lens for sharpness and to see which setting gives you the best result, (using a tripod if possible) photograph a coin or something with similar detail at each different aperture and do a comparison.
 
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#3
The sweet spot is generally 2.5 - 3 stops down from wide open.....I cant say I've noticed a change in colours etc...but by having your lens at its sharpest, the results are going to be the best for that lens....obviously you'll need to have the correct exposure etc.....
 
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#4
Just the sharpening and any distortion really, colour shouldn't be affected.

It's less of a problem on crop sensor cameras as they don't use all the lens, but generally cheaper lenses aren't as good wide open. If you stop down to f8 or so it can improve things.

To test your lens for sharpness and to see which setting gives you the best result, (using a tripod if possible) photograph a coin or something with similar detail at each different aperture and do a comparison.
It is a mistake to think that crop sensor cameras only use the middle of the lens - they use the middle of the image circle which is entirely different. All parts of the lens contribute to all parts of the image. As far as changing the aperture is concerned, the effect will be the same for any sensor used.
 
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#6
The sweet spot is generally 2.5 - 3 stops down from wide open.....I cant say I've noticed a change in colours etc...but by having your lens at its sharpest, the results are going to be the best for that lens....obviously you'll need to have the correct exposure etc.....
Cheers. What about at the other end with a small aperture? Would it be 3 steps or so down as well, or is this only at the large aperture end?
 
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Josh
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#8
Cheers. What about at the other end with a small aperture? Would it be 3 steps or so down as well, or is this only at the large aperture end?
Yes both ends of the range. Most lenses top out at F22, I find on my main lens F16 falls off in detail slightly, F11 is spot on. Do some tests with your equipment to learn it, then you'll always know :)
 

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Nod (NOT Ethel!!!)
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#9
Cheers. What about at the other end with a small aperture? Would it be 3 steps or so down as well, or is this only at the large aperture end?
At small apertures (big numbers), diffraction causes softness so the minimum aperture (highest number) is best avoided. Be careful with steps and stops - the aperture adjustment can vary between 1/3rd and a full STOP per STEP. The full STOP values are in steps of √2 so starting at (an almost hypothetical value of)1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32 etc.. Most lenses are at their best in the middle of their aperture range but sometimes, circumstances might dictate that you NEED to use them wide open or you might want as much depth of field as possible so you need them stopped right down.
To see how your lenses perform, play! For many uses, the diffraction softness might not be a problem.
 
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#10
Cheers. What about at the other end with a small aperture? Would it be 3 steps or so down as well, or is this only at the large aperture end?
The sweet spot of a lens is determined by stopping down from your widest aperture.....unclear why you would want to start at the other end? To get to the sweet spot, you'd end up at the same point. Obviously there will be a trade off at higher fstops, and I'm sure there are experienced landscape togs on here, more qualified to answer that. I always go through the fstops with my lenses in different situations to see how it performs.
 
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#12
I think in the olden days some lenses weren't at their best until something like f5.6 or f8 but these days some of the modern ones are excellent at much wider apertures than those.

Ditto what Lee said. Generally I'd only use the smallest apertures when making a deliberate decision to do so, maybe most often when talking a close up shot of a flower or leaf or something when even at f11 there's next to no depth. And of course as said in another thread recently sharpness isn't necessarily something to worry about too much.
 
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#13
To follow on from all the good advice here. It's well worth taking the time to understand the relationship between aperture, focal length and distance to focal point and how that affects your DoF in different situations.
 
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#14
And of course as said in another thread recently sharpness isn't necessarily something to worry about too much.
Very true. Beside which, there's no point setting the aperture to a particular value if the depth of field you are looking for is compromised.
 
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#15
The sweet spot of a lens is determined by stopping down from your widest aperture.....unclear why you would want to start at the other end?
It based on landscape photos that I had taken recently (at f20-f22 with approx 10/12mm wide angle lens) as I had thought that this would be best to get back to front dof. When mid range (f11 etc) was suggested as this would be nearer to the lens sweet spot, and it got me wondering along the lines of this posts question. You mentioned starting with a wide aperture, but as Im after a long range of sharpness I had been thinking at the opposite end. Hope Ive explained this ok...
 
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#16
I see where you are coming from....as I understand it, for landscape, most togs say f8 to f11, but obviously nothing is written in stone....its what works for your setup and the composition of the shot.
 
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#18
I'd start at DoF tables and I'd also shoot a sequence of pictures starting from wide open and ending at minimum aperture. Doing those two things should give you a good idea of what's going on.

Maybe take a look hyperfocal and zone shooting to see how they work to add to the understanding and look at the Merklinger method too and see if that suits. f20/22 with a wide angle lens seems extreme to me.
 
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