Sharpness

Brendan Mulachy

Brendan Mulachy

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So its generally accepted that a lens is at its sharpest a couple of steps down from its max aperture, now my question is when i put my 1.4 extender onto my 70-200 it's minimum aperture changes from 2.8 to f4...so would my lens now need to be f8 rather than 5.6 ti hit its sweet spot....the things you think of lying in bed
 
Brendan Mulachy said:
So its generally accepted that a lens is at its sharpest a couple of steps down from its max aperture, now my question is when i put my 1.4 extender onto my 70-200 it's minimum aperture changes from 2.8 to f4...so would my lens now need to be f8 rather than 5.6 ti hit its sweet spot....the things you think of lying in bed
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Well I think no, if the sweet spot of your lens without the TC is f5.6 it will still be the sweet spot with it on, though it's effective aperture for exposure will be f8.
 
Well I think…
Why does it matter?
I’m either shooting wide open, or I’m stopping down for an appropriate DoF for the shot.

Knowing that my image could have been measurably ‘sharper’ is purely academic, because the image is the one I wanted to capture.

But we’re all different I guess.
 
Phil V said:
Well I think…
Why does it matter?
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If I'm using one of my f1.2 primes then the aperture I pick is entirely down to what I want to create. But if I use a zoom lens where image detail is not first priority, then add an extender that crops the image heavily to reduce that quality a bit further, I may be wondering if the combination will produce an image that's distractingly soft. In this case the f2.8 zoom should still be decent, but it's a reasonable concern.
 
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I don't think I ever worry about a lenses "sweet spot" - I just use whichever aperture I want or need tbh I also regularly shoot landscapes at bigger apertures than I "should" be using ;) I've probably got a fair collection of f/1.4 'landscapes' if I looked for them :ROFLMAO:

Aside from maybe night skies, there I sometimes stop down a click or two from wide open. Especially if I'm using the Voigtlander 40/1.2 :)
 
JackBell said:
Well I think no, if the sweet spot of your lens without the TC is f5.6 it will still be the sweet spot with it on, though it's effective aperture for exposure will be f8.
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While true, I think that's a bit confusing. If f/5.6 is the sweat spot (f/4 is more likely) that doesn't change necessarily; but when the TC is added the aperture reported by the camera will be f/8 (the effective aperture). So if starting from f/4 with the TC on you would need to stop down to f/8.

Brendan Mulachy said:
So its generally accepted that a lens is at its sharpest a couple of steps down from its max aperture, now my question is when i put my 1.4 extender onto my 70-200 it's minimum aperture changes from 2.8 to f4...so would my lens now need to be f8 rather than 5.6 ti hit its sweet spot....the things you think of lying in bed
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Because a TC can add it's own aberrations the previous "sweet spot" may not be the same. I.e. where previously stopping down to f/8 or f/11 may have caused a small loss of sharpness due to increased diffraction, it might be more beneficial now. And with a fixed aperture lens it may actually be sharpest wide open. E.g. the Nikon 70-200/2.8 S lens at 200mm is sharpest at f/2.8 bare; but it is sharpest at f/5.6 with the 1.4x TC (2 stops instead of one).

But as others have said, technical pixel peeping sharpness should be pretty far down the list of concerns when choosing the aperture for a given image.
 
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Brendan Mulachy said:
So its generally accepted that a lens is at its sharpest a couple of steps down from its max aperture, now my question is when i put my 1.4 extender onto my 70-200 it's minimum aperture changes from 2.8 to f4...so would my lens now need to be f8 rather than 5.6 ti hit its sweet spot....the things you think of lying in bed
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no, you need to take off the tc again to be at the sweetspot. Horrible things....
 
LeeRatters said:
I don't think I ever worry about a lenses "sweet spot" - I just use whichever aperture I want or need tbh
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Pretty much my approach. Indeed, these days I tend to set the camera on "iA" and concentrate on capturing the image I want.
 
sk66 said:
While true, I think that's a bit confusing. If f/5.6 is the sweat spot (f/4 is more likely) that doesn't change necessarily; but when the TC is added the aperture reported by the camera will be f/8 (the effective aperture). So if starting from f/4 with the TC on you would need to stop down to f/8.
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Hi Steven, the confusion was caused by me not realising that modern cameras reported the 'new' aperture caused by the TC. the last time I used a TC was in the 80's when aperture was set on the lens ring and didn't alter when a TC was fitted (obviously) and shutter speed was changed to accomodate the 1 stop loss in light. I used a 50mm f1.8 and 135mm f2.8 for my sports photography back then,supplemented by a 1.5x TC. The lenses were both set at f4, the 'sweet spot' (apologies to anyone offended by this ;) ) on the aperture ring and left there when fitting the TC, thus my reply to the OP.
 
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The sweet spot on the lens is because of the physical properties of the closed aperture blades at the set aperture, the "new Aperture" reported in tthe camera is because the TC is absorbing some light so affecting exposure fooling the camera computer to thinking a smaller aperture is set it isn't physically changing the diameter of those aperture blades. Therefore I submit thet the "sweet spot" of the lens is still the same with or without the TC.

The TC will degrade the image because of the extra lens elements it introduces but it doesn't physically change the lens itself.

In real world shooting tests I have done with my Fuji 50-140 and the 1.4 & 2x TCs I barely noticed the difference with the 1.4 but the 2x was noticable. FWIW the same shots taken with just the lens but cropped to the same image proportions looked just as good as either TC I think the only benefit of the TC was better focus finding of subjects in the far distance because they are larger on the sensor so easier to detect.
 
You could always run your own tests - and then repeat them using a sturdy tripod and remote release. I think that pair of tests would be interesting.
 
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JackBell said:
The lenses were both set at f4, the 'sweet spot' (apologies to anyone offended by this ;) ) on the aperture ring and left there when fitting the TC, thus my reply to the OP.
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Fair enough... I forgot about manual lenses with aperture rings. (y)

Topsy said:
The sweet spot on the lens is because of the physical properties of the closed aperture blades at the set aperture, the "new Aperture" reported in tthe camera is because the TC is absorbing some light so affecting exposure fooling the camera computer to thinking a smaller aperture is set it isn't physically changing the diameter of those aperture blades. Therefore I submit thet the "sweet spot" of the lens is still the same with or without the TC.
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The sweet spot is because the aperture restriction is eliminating (blocking) light from the periphery of the objective element, which is not as well corrected for spherical aberrations; and so improves image sharpness/quality. But stopping down the aperture also increases diffraction, which degrades sharpness/quality. The sweet spot is where the improvement gained is greater than the degradation caused.

A telephoto converter is exactly that. It is intended to convert a non telephoto lens design into a telephoto design; which is why it works best on prime lenses (non-telephoto). And it works exactly the same way a telephoto lens does; the rear telephoto elements magnify the image circle. The magnification spreads the light out, which reduces the light intensity and exposure. And while the aperture restriction hasn't changed, it's size relative to the new focal length has; and therefore the combination has a larger minimum f#.

I.e. a 300mm f/2.8 lens with a 2x TC attached is not "behaving like" a 600mm f/5.6 lens. It IS a 600/5.6, only that it is physically shorter than it otherwise would be (telephoto).
The combination is a new lens design and therefore the sweet spot may change... individual testing should be done if it is of concern. And you might want to test multiple TC's as well; you can get into a situation of compounding errors (usually), cancelling errors (theoretically), or neutral (if you're lucky). Nikon did this for the older 800/5.6, then they sold the TC with the lens and with a matching serial number (that's the main benefit of built in TC's today).

Topsy said:
FWIW the same shots taken with just the lens but cropped to the same image proportions looked just as good as either TC
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That is often the case, or nearly so; especially with today's high resolution sensors. Magnifying the image circle results in a reduction of recorded/total detail much like cropping does; the only difference is which factor limits the resolution more (lens/sensor).

If the lens can resolve far more than the sensor can record, then degrading the lens' resolution with a TC isn't a problem; but degrading the recorded image resolution instead (cropping) would be... this was common back with ≤12MP FF cameras.
Conversely, if the sensor can record (nearly) everything the lens can resolve, then degrading the lens' resolution would be a problem; and cropping would not be... this is more common with 20+MP cameras today.

Not sure why I felt the need to explain all of that... :thinking:
 
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Because it's interesting, if not much use in the real world!
 
I'm more interested in the aesthetics of the image rather than if they're 1 or 2 points sharper and so I don't bother much about the sweet spot. That being said I do have a baseline of what is acceptably sharp therefore I buy lenses that are plenty sharp enough wide open, this way I can concentrate on the overall image rather than worrying about whether it's in the "sweet spot" or not. The only lens I have where this is not the case is the 16-35mm, but this is for landscapes and I know I'm going to be at f8-11 anyway.
 
snerkler said:
I'm more interested in the aesthetics of the image rather than if they're 1 or 2 points sharper and so I don't bother much about the sweet spot. That being said I do have a baseline of what is acceptably sharp therefore I buy lenses that are plenty sharp enough wide open, this way I can concentrate on the overall image rather than worrying about whether it's in the "sweet spot" or not. The only lens I have where this is not the case is the 16-35mm, but this is for landscapes and I know I'm going to be at f8-11 anyway.
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That's true for me too. But I have found with some lenses that operating outside the sweet spot I can see the low resolution even at TP display sizes, and that is issue for me. It's only relatively recently that I've stopped having to worry about whether the lens will hold enough detail in the corners to look OK
 
snerkler said:
therefore I buy lenses that are plenty sharp enough wide open
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That's a little bit of a luxury; or quite the luxury when we start talking about the really long focal lengths TC's are used for.

But still, good photography is more about content than it is about technical quality. Aperture for depth of focus instead of absolute sharpness; and ISO to get the required SS instead of absolute minimum noise. Even when you have the opportunity to optimize all of the settings, it still won't matter if the content is boring.
 
sk66 said:
That's a little bit of a luxury; or quite the luxury when we start talking about the really long focal lengths TC's are used for.

But still, good photography is more about content than it is about technical quality. Aperture for depth of focus instead of absolute sharpness; and ISO to get the required SS instead of absolute minimum noise. Even when you have the opportunity to optimize all of the settings, it still won't matter if the content is boring.
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Yep I'm very fortunate to have the gear I have, although it has taken many years to get there (y)
 
Sharpness in photographs generally is something I used to worry about forty years ago. But I've grown out of that. And why anyone would want a photograph to be sharp into the corners is somewhat beyond me.

What is this thing with corners? Can't they be allowed to recede gracefully? Think of the picture space as a whole. You want it to stop with a BANG when it gets to the edge?
 
I read a nice one that made me chuckle the other day,

An amateur worries about sharpness
A pro worries about money
A photographer worries about content
 
droj said:
Sharpness in photographs generally is something I used to worry about forty years ago. But I've grown out of that. And why anyone would want a photograph to be sharp into the corners is somewhat beyond me.

What is this thing with corners? Can't they be allowed to recede gracefully? Think of the picture space as a whole. You want it to stop with a BANG when it gets to the edge?
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Don't you shoot landscapes? For the right framing it looks so much nicer to hold detail to the edge of the print. If I want soft corners then that's a choice I make, but not something I want forced on me by poor equipment. This is NOT really about sharpness, but about intent and look.
 
ancient_mariner said:
This is NOT really about sharpness, but about intent and look.
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Of course it is! But one of the most valuable attributes of an image may be its 'heart' - a source of it's greatest richness. Which is less definable, & more particular to the individual viewer. But nevertheless, we're involved with photography as a medium of communication, aren't we? (to make any sense of why we do this at all) - so it's as well to try to describe some of its parameters.

What of the pinholers, free-lensers & Holga-maestros? Do they get a look-in to your universe?
 
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I think that the purpose of most photography is to show others what you saw.

If your pictures achieve that, I think they are good pictures.
 
droj said:
What of the pinholers, free-lensers & Holga-maestros? Do they get a look-in to your universe?
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If people want to use them for creatively enhancing their images then that's fine, but generally they just sod up a potentially interesting pucture. These effects are like playing guitar with a fuzz pedal on all the time - it works in the right place, but otherwise detracts.
 
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ancient_mariner said:
If people want to use them for creatively enhancing their images then that's fine, but generally they just sod up a potentially interesting pucture. These effects are like playing guitar with a fuzz pedal on all the time - it works in the right place, but otherwise detracts.
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or make a boring scene, reproduced a thousand times, unique and more interesting
 
Barney said:
or make a boring scene, reproduced a thousand times, unique and more interesting
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Perhaps, but a boring scene will still be a boring scene with a gimmick in front. A bit like spot colour in otherwise mono photos, an effect used well can enhance an already potentially good picture, but otherwise it's just another gimmick.

It's worth adding for balance, that I recognise we don't see things the same. Some love polaroid pictures, for example, whereas for me they were always rubbish and very very unsatisfying even when it was a new technology. I can remember how disappointing they were when I was a child, even without adult standards to judge against.

I'm not opposed to trying different photographic effects if they add something. Gav's IR portait is effective because of the way it enhances the skin of his subject. https://www.talkphotography.co.uk/threads/ir-portrait.771293/#post-9671161
 
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ancient_mariner said:
I'm not opposed to trying different photographic effects if they add something. Gav's IR portait is effective because of the way it enhances the skin of his subject. https://www.talkphotography.co.uk/threads/ir-portrait.771293/#post-9671161
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At the end of the day, we all have our likes and dislikes.

My opinion is we should accept that not liking an image proves only one thing: we don't like that image. Conversely, liking an image only proves one thing: we like that image.
 
ancient_mariner said:
If people want to use them for creatively enhancing their images then that's fine, but generally they just sod up a potentially interesting pucture. These effects are like playing guitar with a fuzz pedal on all the time - it works in the right place, but otherwise detracts.
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I think that the fashion for super sharp lenses with sharpness everywhere on pictures is like music that is on the beat.

Some people want to listen to music that is dead on the beat. Some people want to listen to music which swings. Some people want to listen to ragtime.
View: https://youtu.be/UL_Hsf14IeE?si=UMj7LqZA0DgypnX9


Sharpness across a picture is not how anyone sees at the World. It is a perfectly valid choice (one I've used a lot) but it doesn't have to be.
 
Erty said:
I think that the fashion for super sharp lenses with sharpness everywhere on pictures is like music that is on the beat.

Some people want to listen to music that is dead on the beat. Some people want to listen to music which swings. Some people want to listen to ragtime.
View: https://youtu.be/UL_Hsf14IeE?si=UMj7LqZA0DgypnX9


Sharpness across a picture is not how anyone sees at the World. It is a perfectly valid choice (one I've used a lot) but it doesn't have to be.
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As a gigging musician, I have to suggest this analogy is incorrect. It's the player or photographer who decides whether to carefully follow a click track or play rubato, to decide whether they want their picture sharp front to back, selectively sharp or blurred all the way through. When you select a lens that cannot resolve detail clearly it's like picking up an instrument that is out of tune and won't stay in time with the music - there are a small number that like this kind of thing and I've had tone generator effects in processors that produce random-sounding beeps and bops - but they don't work for most music creation. Very few musicians would want an instrument that could only work that way. But instead you use a guitar or keyboard that is versatile to create the sounds and rhythms that you want to bring the best out of the music, just as you would a decent lens to bring the best out of the subject and convey the message that you want to share.

In the end it's not the sharpness of itself that matters, but if you can only produce images that are indistinct then you are very restricted in the feelings that can be communicated. I would rather choose how I follow the beat, whether playing one of my guitars or deciding what parts of a photo should be sharply detailed and which parts not. But as I've said before, if the first thing people notice about your picture is the poor technical quality then the image has already failed to communicate.
 
AndrewFlannigan said:
At the end of the day, we all have our likes and dislikes.

My opinion is we should accept that not liking an image proves only one thing: we don't like that image. Conversely, liking an image only proves one thing: we like that image.
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I can not like an image, but appreciate the time and trouble that the photographer went too to obtain and process the image as they thought best. I like that.

I also like that an image was created at all, Whether I like the finished product or not.
 
Barney said:
I can not like an image, but appreciate the time and trouble that the photographer went too to obtain and process the image as they thought best. I like that.

I also like that an image was created at all, Whether I like the finished product or not.
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Yes. And to continue @Erty 's analogy...I can apreciate the skill, talent and time it takes to create great opera...but to me it is still some bint in a frock screeching at me! :cool:
 
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