Lens "Sweet Spots"

Carlh

Carlh

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One of my repeated C&Cs against my various pics was for poor focussing, which confused me as I thought I had pretty much managed to use the manual focussing ok. I even thought perhaps my eyesight was off and I needed an eye test :gag:

In an effort to get my pictures sharper () Id heard the catch-word "sweet-spot" on TP.

Googling sweet spots, I found a few web pages where people ran real-world comparisons of various F-stops on a particular lens, to find the "sweet spot".

Have a quick read of this, if you dont mind:
http://improvephotography.com/2449/what-is-the-sharpest-aperture-on-a-lens/

To my amazement, I could not believe that the sweet spot on a 50mm f1.8 was actually f7.1

I tried it, at 1.8, then 4, then 7.1 then 8 and 11
The only problem was the wind has been blowing between shots so I couldnt get a set of comparable images myself. The article above basically shows the end result, and I think anyone who is interested in getting the sharpest quality out of their lens, should also run some tests of your own and maybe add them to this thread? :)

At 7.1, the sharpness of a subject was, well, it blew me away.

On the Tamron 70-300mm, the sweet-spot seems to be F8 for me.

If everyone ran a test, as described in the article, maybe not a newspaper, but a stationary object with considerable detail, such as a coin or brickwork, preffably on a tripod so you can clearly compare them yourself, make a note of the F-Stop of the clearest, sharpest image from your test and post the lens and F-stop info in this thread, we could build a little table of sweet-spots on everyone's type of lens.

I also recommend manual focussing for maximum sharpness, unless of course you dont trust your eyes :)

Heres the table so far:
Canon 50mm F1/8 - F7.1
Canon 10-22 - F8.
Tamron 70-300mm - F8
Sigma 12-24mm f4.5-5.6 - f8
Nikkor 18-200mm f3.5-5.6 - 18-70mm f5.6-f8
Nikkor 35mm f1.8 - f4
Nikkor 18-55mm f3.5-5.6 - f8
Nikon 35mm f1.4 and 85mm f1.4 the sweet spot is 1.4

Now, you may have one of the above lenses and get a different "sweet spot" - thats fine, what I would suggest is that if a majority of people have the same sweet spot for a lens and someone else with the same lens has a different sweet spot, we'll go with the majority? Sound fair? :)

Post away!
 
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Sorry to put a downer on it, but I am not that fussed about the sweet spot. It is always a few stops from max aperture anyway isn't it? I use whatever aperture I need or want at the time so what difference does knowing the sweet spot really make?

It still sounds like you have focusing issues if people are specifically commenting on it and maybe looking to blame the lens and the fact it was not in it's sweet spot?
 
Chris, how can you not be fussed on how sharp you can get your images?

I thought it was supposed to be a few stops from max, like yourself, but actually testing it, F7.1 is seems to be (for me) better than F1.8 on the 50mm.

Heres an example I took just an hour ago or so, before it started to rain :( I couldnt run the same test, the bee flew away and I was getting wet.

IMG_8367.jpg


I dont think Ive managed a sharper image. Im confused and think it would be interesting to hear if anyone else has any opinions on this?

Ive just been reading a bit more on this, there is a general consensus of 2 to 3 stops below smallest aperture but also, it alters from same-lens to same-lens (which seems weird to me).
Would be still good to generate a table of this information and see if there is a pattern of "best aperture" per lens? :)
 
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Carlh said:
Chris, how can you not be fussed on how sharp you can get your images?
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I didn't say I wasn't fussed about how sharp my images are , I said I wasn't fussed about the sweet spot.
Maybe it is just my lens but I see no noticeable difference between 2.8 and 10 and am happy with it so I use the aperture I want rather than worrying about using something like 7.1 to get the absolute maximum sharpness possible. If my lens was dreadful at 2.8 but great at 7.1 I may think differently...
 
This might sound controversial but I'm with Mark on this, it's just the gear that we use to capture our vision of reality - when we start thinking too much about the gear, the important stuff goes away.

There's a risk we'll turn into those guys who buy D800's and Zeiss glass and like to boast how sharp the picture of their cat laid on the settee is, unremarkable cat, unremarkable settee, unremarkable light but you can count the eyelashes on the cat:shake:

All the while there's guys with D3100s and kit lens producing gorgeous landscape shots using a beanbag to steady their camera.

I'm vaguely aware of where my gear produces it's best results, but if they're not the settings I need to get the shot I want - what's the point of that knowledge.
 
We just need Mark to join the thread now so we can see what you agree with :)
 
lol@phil, who's mark? ;) i guess its chris you're referring to :)

I do get you both - getting carried away with tinkering with the functions of a camera can lose the objective of getting a great photo. Ive had it happen to me.

I simply created this thread to see, what other people's "sweet spots" are. If no one decides to participate thats fine, my signature is my excuse - Im a dumb noob.

I want to be able to produce high-quality, great content photography using the equipment that I have. I dont have particularily brilliant equipment but I do want to get the most from it and I imagine others do to. Hence this thread.
 
Sigma 12-24mm f4.5-5.6 sweet spot at f8
Nikkor 18-200mm f3.5-5.6 sweet spot at 18-70mm f5.6-f8
Nikkor 35mm f1.8 sweet spot at f4
Nikkor 18-55mm f3.5-5.6 sweet spot at f8

not ran as comprehensive test as yours, as i am with "Mark" on this one. but i do test my lenses when it comes under my possession.

with exception of kit lens, the first 3 lenses are always with my camera:
-i always use UWA at f8 or f10 because it's a wide angle lens, everything need to be in focus.
-the 18-200mm is my walk about lens, i live by "f8 and be there" during sunny days, f5.6 cloudy days. it has never let me down. i'm not afraid of using other apertures to get the shot.
-the fast prime is really for low light otherwise the super zoom is used, so the 35mm is wide open all of the time.
 
thanks mark - you also make sense and I suppose its a choice over DoF versus sharpness and to either find a balance or sway more to either for the appropriate look that the tog is after. I suppose thats going to change from shot to shot as well, not every subject is xx amount of feet away.

Thanks Wuyan :) those figures will be handy and the tips of what you're using depending on the daylight available will be very useful (I'll be using them).

Again - I do apologise for my dumb questions, hopefully I can help noobs on things like this when Im as experienced as the rest of you :)
 
Don't count me in the list of experienced people. I am just an opinionated newcomer. :)
 
I'd be more interested in finding the best balance of sharpness vs Bokeh so you retain the best Bokeh with reasonable sharpness. I'd value Bokeh over sharpness.
 
It is an interesting subject and I can see both sides of the coin.
As I mainly shoot landscapes, I frequently used the Canon 10-22 and in my opinion the sweet spot was F8.
Now having switched to FF and using the Canon 17-40, I have yet to find it, but I suspect it may be around f16. Something to do with FF v crop I think, but as others would say HoppyUK will be along shortly to explain:)
 
To throw a spanner in the works....

Both the Nikon 35mm f1.4 and 85mm f1.4 the sweet spot is 1.4. No need to stop down, heh.

Also, no two lenses are the same. Ive had a couple of 50mm's, with varying sweet spots between f1.8 and f4.

Kind of a bit of a pointless exercise, listing then here. Sure it's a good thing to know for your own lenses, but only if you are really bored and/or a total pixel peeper.

Otherwise, not much use tbh
 
markmullen said:
It is fine going for the sweet spot of the performance of your lens but if the shot doesn't work because the DoF isn't right then you're worse off.
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My views are the same.

For example: If i was shooting low light and had to compromise between using a wider aperture and losing sharpness over increasing the ISO and gaining noise, I'd always elect to use a wider aperture...

I agree though that sometimes lenses look better at certain apertures than others, but I would always chose the desired DoF before wondering if it's at 'max sharpness'
 
Here's my views on lenses and sweet spots...

Its great to get the best image quality possible, including but not exclusive to sharpness...but unless a lens is at least "good" on the sharpness scale wide open, I won't touch it - Nikon 50mm f1.8D for example. Had it, never used it, bought the new one :)

At lest if its good wide open, you won't be worried about sweet spots.
 
markmullen said:
It is fine going for the sweet spot of the performance of your lens but if the shot doesn't work because the DoF isn't right then you're worse off.
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100% agree. If I can be in the 'sweet spot' to achieve whatever it is I want to achieve then I'll do it but not if it means changing what it is I wanted, for example I used to use a Tokina 11-16 which was wonderful at F/5.6. I knew that at the wider end that would get me an enormous depth of field if I was sensible with my foregrounds so that aperture was pretty much where the lens stayed.

My 50 and 85mm 1.4's are probably both at there sweet spot at something like F/5.6 but who buys a fast prime for that? I often use those wide open or stopped down just a fraction.

One last exception to prove the rule, I have a Voigtlander 20mm lens which is a bit of jekyll and hyde of a lens in that it is poor wide open and even stopped down a little but sings at F/8 or F/11 so I never use it for anything else. Not a problem as I bought it for landscapes but it would be if I wanted to get cretive with dof.
 
For me, as a beginner, sharpness in a picture is a priority, most people new to photography struggle to get sharp focus, maybe is slow shutter speed or wrong aperture, camera shake, no tripod or just wrong focusing mode, in a nutshell, I don't have a clue.

I was really surprised when I read about "sweet spots" and find out my nifty fifty wasn't at is best at f1.8, in my mind, it was already cataloged as a lens for low light only because of the wide aperture, so I was using it at f1.8 mostly. The "sweet spot" concept really opened my mind to see that you have to play with the exposure triangle to get best results.
 
Simon photo said:
And there is nothing worse than a sharp image of a fuzzy concept
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:lol: that'll be me then !

freyuk - exactly the reason why i bought my 50mm, in my head it was deemed "perfect" for low light shooting (and it is, and im happy with that).

Most of my shots are between 80th and 125th of a second, id love to just shoot at 250-300th but normally the light isnt available to do that, or i have to throw up the ISO, which then gives me the noise i <dont> want.

I really admire the togs who have this down to a fine art. There is just so many things to evaluate in such a short space of time to obtain a great image. I tip my hat off to you.
 
freyuk said:
For me, as a beginner, sharpness in a picture is a priority, most people new to photography struggle to get sharp focus, maybe is slow shutter speed or wrong aperture, camera shake, no tripod or just wrong focusing mode, in a nutshell, I don't have a clue.
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Yes a beginner should aim to get the picture in focus but that is not related to lens sharpness, shutter speed, camera shake or knowing when to use a tripod and more to do with knowing how to focus.
Once all those things are mastered you may then (or may not) worry about the lens being used giving the ultimate sharpness it can. Looking at lens sharpness first could lead to the user blaming that rather the lens rather than poor technique. Sharp photos should be able to be obtained with an 18 - 55 kit lens...
 
Surely this all comes down to using the right tools for the job, understanding DoF and more importantly the perception of sharpness.
If you use a 50/85 f1.4 wide open to take a portrait shot, then the only thing which will be "sharp" is the spot which you have focussed on - possibly/hopefully the nearest eye of the subject. If you then use the same lens to take a group shot, further away, then you will use a smaller aperture - from f5.6 to f11, and as long as you focus on the centre person in the group, the whole picture will appear to be much sharper than the portrait shot, and this is because of "perceived sharpness".
The only genuine sharpness test of any given lens, is to rig up a tripod, and take shots at all apertures, finally checking the resolving power, clarity and any image distortion.
 
sharpness is nice to have but if you want to have small DOF you need to shoot at large apertures. finding a sweetspot for your lens while 'fun' for you it is pretty much utterly useless for most people. Also different sensors will have different max sharpness too.

Carlh said:
Chris, how can you not be fussed on how sharp you can get your images?
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FoCal Pro will plot sharpness vs aperture for a lens, if that's the kind of information you might find useful. Actually it will do it even if you have no use for the data at all. :)

http://www.reikan.co.uk/focalweb/index.php/tests/aperture-sharpness/

Depending on your gear it might be very useful to realise how sharpness alters by stopping down a bit. e.g. you might find that using a 100-400 zoom lens at f/8 and 400 ISO will yield much better results than shooting wide open at 200 ISO, even when DOF is not necessarily a significant concern.
 
I'll use the Aperture for the depth of field effect that I want, or I'll use a wide Aperture to get a a fast enough Shutter rather than raise the ISO, but if the subject has no depth, or the depth of field doesn't matter, then I'll go for the Aperture that gives me the sharpest image.

Taking a picture of a building springs to mind.
 
redhed17 said:
I'll use the Aperture for the depth of field effect that I want, or I'll use a wide Aperture to get a a fast enough Shutter rather than raise the ISO, but if the subject has no depth, or the depth of field doesn't matter, then I'll go for the Aperture that gives me the sharpest image.

Taking a picture of a building springs to mind.
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I do it the other way round the majority of the time (unless I'm doing dof work). speed-Sharpesed aperture and then followed by ISO. When ISO creeps up past an acceptable level, my aperture cones down then ISO up if needed and last resort is shutter speed. In my head I want the whole picture to be at its best and sharpness is important but I believe there is a threshold you should go below and that threshold is soft lenses or soft apertures in certain lenses...I'm not really that bothered about sharpness since all my lenses are good wide open!
 
Thanks all.

The positive comments have been great, links to sites containing some great information and even lens testing capabilities.

Other comments confirming that the sweet-spot is worth knowing, even if it isnt going to be a driving factor of the picture being taken, if, if maximum detail is needed, at least being aware that there is a sweet spot (I wasnt) and utilising it when required IS very VERY useful.

I have done an indoor church shooting, knowing the sweet spot was there, would have at least given me the knowledge that I might be able to squeeze a bit more detail out of the beautiful building and I would have taken a few snaps at that aperture.

I'll run some tests this weekend...
 
Just to add to the mix, if it is maximum sharpness you're after then shouldn't the diffraction limit of the camera sensor also play a part as even if you hit the s spot on the lens, the image may be softer than it could have been.

As most people I find the tech side of photography very interesting, as long as you dont let it dictate how you photograph things.
 
Peter10d said:
It is an interesting subject and I can see both sides of the coin.
As I mainly shoot landscapes, I frequently used the Canon 10-22 and in my opinion the sweet spot was F8.
Now having switched to FF and using the Canon 17-40, I have yet to find it, but I suspect it may be around f16. Something to do with FF v crop I think, but as others would say HoppyUK will be along shortly to explain:)
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Sorry for the delay :D

While I find all this kind of thing interesting, it's one of those 'know it and then ignore it' jobs because there are almost always other considerations that take priority in real shooting. And if you really want to max out the sharpness, then you'd better be very careful with focus and use higher shutter speeds than the usual reciprocal of focal length rule of thumb.

The sweet spot of max sharpness is the cross-over point where the reduction of aberrations gained by raising the f/number is overtaken by the increasing impact of diffraction. That's dependent on sensor format, but since diffraction is independent of lens quality it almost always boils down to f/5.6 on crop format and f/8 on full frame, though a few very high quality lenses might peak at slightly lower f/numbers than that (and at a higher level). There is also the theory concerning pixel density but frankly I don't hold with that one much.

With many lenses (wide zooms being an example) the edges lag quite a long way behind central sharpness, so they peak later (and lower). It's not uncommon to see central sharpness peak at f/5.6 and the edges continue to improve until f/11, when the centre will have got worse of course. Depending on your priorities, in that case a landscaper might go for f/11 as the best overall compromise.
 
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thats really handy to know richard, i like taking all sorts of photography. There are so many variables to consider and at the end of the day, I guess its going to come down to the photographer's eye.
 
Might I add based in the church comment:

For low light, sweet spots are thhe last variable to consider - mostlikely you will get a better detailed shot with a wider aperture and lower ISO as it will be creeping into the region of losing detail.
 
To read some of the replies here you'd think the tripod was yet to be invented. What's wrong with the sweet spot and 1 second (or whatever it takes) at 100 ISO on a sturdy tripod with MLU etc. etc.? It's not compulsory to use fast shutter speeds all the time and it isn't always necessary to whack up the ISO just because you're stopping down a bit. There are other cat skinning options. And let's not forget the power of flash to freeze shake/motion too.
 
I have never bothered to test a lenses sharpness across the lens at different aperture before but this thread led me to - damn you stupid thread, damn you.

I only have one lens (get your violins out) and that is a Canon 40 2.8 STM.

In my non scientific shots of a fence I found that my lens seems to be the same in the centre at various apertures but surprisingly the sharpest I got at edges of frame and corners was at 2.8.
The differences were actually small (only noticeable on 100% crops) and I was happy with all of the images at all apertures but good to know that rather than potentially losing at 2.8 I may be gaining.

I realise I am in a lucky position of finding an entry level DSLR with a £140 lens on it as sharp as I need and the camera will never be at fault.
 
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