Lens sweet spot?

Messages
415
Name
Ciaran
Edit My Images
Yes
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?
 
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.
 
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.....
 
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.
 
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?
 
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 :)
 
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.
 
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.
 
I usually shoot with an aperture that will give me the look and DOF I want for the particular image I'm taking and the scene I'm faced with. That can be anywhere from f/1.2 to around f/9..... Sometimes I might go smaller but f/11 is usually the smallest I use.
 
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.
 
Last edited:
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.
 
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.
 
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...
 
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.
 
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.
(y)(y):)
 
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.
 
Having used Reikan FoCal, all my Canon lenses are sharpest 1-2 stops down from widest aperture. However as others have said ultimate sharpness isn’t always the goal and sharpness doesn’t fall of a cliff outside those until you get to really small apertures.
 
Personally, I never cared for such a thing.

Get the look that you want, the image in your mind comes first, so be it if it's 5% less sharp wide open. Don't worry about it, don't stop down just for sharpness over the intention of the image

(unless sharpness is what you are after).
 
In terms of central sharpness, that reaches maximum at the aperture where aberrations which are reduced by stopping down, meet diffraction. Diffraction is an unavoidable aberration that effects all lenses equally, regardless of quality, and it gets worse as the f/number goes higher.

The best lenses reach their peak at lower f/numbers, maybe as low as f/2.8, and at a very high standard of sharpness. Most good lenses typically peak around f/4-5.6, at a slightly lower level; some don't peak until f/8, and at a lower level again. After that, sharpness reduces more as diffraction gets progressively worse.

But all that is only in the centre of the image. Most aberrations are more prominent around the edges of the frame and sometimes the edges go on improving with further stopping down, even after the centre has passed its peak. So, if overall sharpness across the whole image is important, then that might well be at a slightly higher f/number than peak central sharpness.
 
Don’t get bogged down by all the technicalities, learn the art first, the science bit you can pretty much overcome with the sheer force of money, the art part is harder to buy.

plus on a 1000px photo, a touch it sharpening in LR, looking at it on a 6” screen phone, most people can’t tell. If you are shooting for clients then that’s different but by that point one would hope you know all this by then and have gear that don’t suffer much in these areas. So really, don’t worry about it, just shoot photos.
 
Back
Top