Lens Specification - confused

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Vectorially

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Can someone please help educate this noob trying to understand the the highlighted specs of this lens?

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My first thoughts were "how can the lens have f/22 aperture yet the aperture range be only between f/4.0 and f/5.8?"

Does it in fact mean that the maximum apertures lie between f/4.0 and f/5.8 depending on the amount of zoom applied, and that regardless the minimum aperture accessible at all levels of zoom is f/22?

If the latter is correct, how do you know what the minimum aperture is when just looking at what's printed on a lens (as opposed to having to find and download a copy of the manual to check the specs)?
 
Vectorially said:
Does it in fact mean that the maximum apertures lie between f/4.0 and f/5.8 depending on the amount of zoom applied, and that regardless the minimum aperture accessible at all levels of zoom is f/22?

If the latter is correct, how do you know what the minimum aperture is when just looking at what's printed on a lens (as opposed to having to find and download a copy of the manual to check the specs)?
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This is correct. You can either find out in the manual/reviews or put the lens on the camera and see when zooming in.
 
Vectorially said:
Does it in fact mean that the maximum apertures lie between f/4.0 and f/5.8 depending on the amount of zoom applied, and that regardless the minimum aperture accessible at all levels of zoom is f/22?
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Yes.
Vectorially said:
If the latter is correct, how do you know what the minimum aperture is when just looking at what's printed on a lens.
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For many modern lenses, you don't. Of course, you can put the lens on a camera, switch to Aperture Priority mode and see how small an aperture you can set.

Alas, it's not a perfect world... :naughty:
 
As others have said it's correct. Basically this variable maximum apature occurs on cheap lenses, because it's cheaper to make them that way.
 
You probably don't really care what the minimum aperture is. It is pretty much always something much smaller than what is really useful for most digital cameras... (I can't think of an exception).
 
sk66 said:
You probably don't really care what the minimum aperture is. It is pretty much always something much smaller than what is really useful for most digital cameras... (I can't think of an exception).
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Hell, no. There are loads of scenarios and situations I use f22 for, and I have lenses which specifically go to f45 and f128, and I'm using those at that end.
 
Bobsyeruncle said:
Yeah, but most people don't either go to f22 or have f45 and f128 lenses.... ;)
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Yeah, but the previous poster I replied to said he couldn't think of an exception to using minimum apertures.
and many people wouldn't use f22, because they don't know what they are doing and / or don't have the correct equipment that will allow them to shoot like that and / or are using cheap lenses that don't look good at f22 or indeed wide open and will then start a big discussion about the 'sweet spot'
 
Hah, you thought you were going to get away with asking this question without any math. Sorry, buddy.

The "F" in f-stop stands for focal length and is usually written like f/4. That's an equation. Focal length divided by 4. And the result of that equation is the diameter of the aperture. The diameter of the hole that lets in the light. And a bigger hole lets in more light.

Using round numbers, say you have a 50mm lens with a max aperture of F/2, the hole would be 25mm wide. If you increase the focal length of the lens to 100mm without increasing the size of the hole, which is basically how variable aperture zooms work, now that 25mm hole works out to f/4 at 100mm.

That's why those huge sports telephotos are huge. A 600mm lens needs a 150mm aperture to achieve f/4. And that opening needs a giant front lens element to cover it up.
 
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riddell said:
Hell, no. There are loads of scenarios and situations I use f22 for, and I have lenses which specifically go to f45 and f128, and I'm using those at that end.
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Like for what? Large format format sure, that's why I specified digital. I know some will go well into diffraction limiting for macro work, and I can understand that choice; but most will use/suggest stacking instead as a better option (for IQ).
 
sk66 said:
Like for what? Large format format sure, that's why I specified digital. I know some will go well into diffraction limiting for macro work, and I can understand that choice; but most will use/suggest stacking instead as a better option (for IQ).
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Architecture. Landscapes, products. Why would you do anything such as focus stacking if you can avoid it? What do you think photographers did before focus stacking was an option?

So take one single shot correctly at f22, which if you are shooting tethered you can see immediately on the screen, perfect. Next shot. Time: Less than second.

Or two, take multiple shots, all of which risk your camera moving, or the product or environment moving, wind blows, products slip, fabrics slump. Light changes. Clouds move. All of which will affect any focus stacking.
Then you need to transfer all the images, load them into software, process and so on. Time: at least a few minutes and potentially a less than perfect shot.
 
ancient_mariner said:
Diffraction. [emoji6]
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With a full frame sensor and printing at 10 x 8 inches, diffraction softening becomes apparent with a physical aperture of around 3mm.

If you are using a 600mm lens and set it to f/22, the physical aperture will be shy of 30mm (600/22). So printing at 10 x 8 inches will be fine. If fact, with a 600 mm lens, diffraction softening will not be apparent below f/120 or there abouts.

At f/22, you can use a lens of more than 66mm focal length with no diffraction softening at the 10x8 inch print size.
 
john.margetts said:
With a full frame sensor and printing at 10 x 8 inches, diffraction softening becomes apparent with a physical aperture of around 3mm.
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At what viewing distance? And if I want to print bigger than that (which I do if I make prints - usually 12" X 16" minimum, sometimes 20" X 30") what aperture am I limited to with a 28mm lens?

And if I happen to pick up my wife's M43 camera - like the one the OP is using - what aperture will I be limited to at 14mm if I want to make a 12" X 16" print? Pretty sure it won't be f22

I'm sure these things can be easily calculated, but who CBA to do it when they're out & about.
 
ancient_mariner said:
At what viewing distance? And if I want to print bigger than that (which I do if I make prints - usually 12" X 16" minimum, sometimes 20" X 30") what aperture am I limited to with a 28mm lens?

And if I happen to pick up my wife's M43 camera - like the one the OP is using - what aperture will I be limited to at 14mm if I want to make a 12" X 16" print? Pretty sure it won't be f22

I'm sure these things can be easily calculated, but who CBA to do it when they're out & about.
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This is true, but choosing an arbitrary f-number to avoid diffraction effects is foolish. When I am photographing wildlife with my 600mm lens, I am not going to get diffraction softening at any available aperture. With my 10mm lens, I am going to get it at every available aperture. Between those two limits it is variable - and not very important.
 
john.margetts said:
...and not very important.
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I think that for virtually all photography, that's the key statement about diffraction. For those cases where it is important, the person making the exposure almost certainly understands what s/he's doing.
 
john.margetts said:
With a full frame sensor and printing at 10 x 8 inches, diffraction softening becomes apparent with a physical aperture of around 3mm.
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Diffraction does not relate to a specific physical aperture diameter.
Diffraction is due to a light path obstruction which is the entrance pupil; which is defined by the f#. The entrance pupil/f# is the effective size of the physical aperture restriction as magnified by the objective element(s). And all lenses will project the same size airy disks at the image plane when set to the same f# (assuming no additional optical errors).

When the airy disks are smaller than a pixel they are not resolved (individually), when they are the same size as a pixel they are resolved perfectly, when they exceed the size of a pixel contrast decreases, and when they exceed ~ 2x the size of a pixel recorded resolution decreases... if they exceed the size of a pixel by 4x the recoded resolution will be less than when at 2x.

Now; whether you will see these effect, or if you even care, is another matter...

Here's a technical paper on diffraction: Do sensors outresolve lenses' capabilities?

Edit: it just occurred to me that your 3mm limit for an 8x10 print is probably the 30micron airy disk (FF CoC limit) magnified/enlarged to .3mm in the print. FWIW, the CoC limit(s) are quite arguably insufficient for modern usage (digital display)... and it's arguable that it was never actually sufficient (I calculated that it is based on ~ 20/40 vision).
 
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So back to the original enquiry, the user is on M43 kit which DOES demonstrate noticeable diffraction issues at smaller apertures. It's not helpful to the user here to tell us that you have successfully taken pictures with the iris screwed so tight the blades squeaked, and since Ansel was using 10x8, diffraction was going to be invisible on any print he might make.

We've had several users ask why their pictures weren't sharp previously, and at least in some cases it's because they've used f22 looking for the most depth of field. Let's try to be helpful, rather than either willy-waving or trying to out 'devils advocate' each other.
 
In practical terms Diffraction is a non issue for a majority of people.
Stopping down a leans does three main things, it decreases the light, it increases the depth of field, and increases the effect of diffraction.
The first two are useful, and even diffraction can be.

Diffraction sets the maximum sharpness possible for any lens aperture . If your lens can close to f22 and is diffraction limited. everything with in the scope of its depth of field will appear equally sharp. However if it is not diffraction limited the lens will appear sharper at its plane of focus than anywhere else.
With large format and architectural photography, this property of diffraction can give images that appear equally sharp all over, with out any apparent fall off.

However they will not be critically sharp anywhere.

It is much the same effect as you get with a pinhole camera, where every thing is equally unsharp. But in the case of diffraction it only puts a limit on sharpness.

If a lens appears to you to be satisfactorily sharp at its smallest aperture, diffraction for you at least is irrelevant.
for anyone who only ever sees enprint sized prints, or on their computer screen, this is always the case.
 
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Terrywoodenpic said:
f your lens can close to f22 and is diffraction limited. everything with in the scope of its depth of field will appear equally sharp. However if it is not diffraction limited the lens will appear sharper at its plane of focus than anywhere else.
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The lens is always sharpest at the focal plane whether diffraction limited or not. Increasing the DoF can make everything within it acceptably sharp (that's what DoF/CoC define).
And if the image is viewed small enough everything w/in the DoF can appear equally sharp because the largest blur radius is at the minimum limit of your ability to see; but that is also a loss of (visible) resolution.

FWIW, the loss of resolution isn't always a big deal... the tradeoff can be worthwhile. For instance, in macro work the small details lost may be things you do not even know exist, and therefore you do not notice that they are missing. And if you are making artistic images things like contrast, mood, etc, are much more important.

F/128 on a FF sensor is only ~ 1MP recorded (median/green wavelengths) and it is not something I would do or generally recommend... but maybe that is sufficient for you (Paul) because you are only going to put it online at 1024px long edge (<1MP); or maybe you don't actually care about/need much resolution at all.
 
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It occurs to me that if Ralph Waldo Emerson had been a keen photographer he might have rephased his famous aphorism as "sharpness is the hobgoblin of obsessive photographers, adored by self described artists and those who prefer a boring image to an interesting one".

I shall now exit smartly to the left... :exit:
 
sk66 said:
The lens is always sharpest at the focal plane whether diffraction limited or not. Increasing the DoF can make everything within it acceptably sharp (that's what DoF/CoC define).
And if the image is viewed small enough everything w/in the DoF can appear equally sharp because the largest blur radius is at the minimum limit of your ability to see; but that is also a loss of (visible) resolution.

FWIW, the loss of resolution isn't always a big deal... the tradeoff can be worthwhile. For instance, in macro work the small details lost may be things you do not even know exist, and therefore you do not notice that they are missing. And if you are making artistic images things like contrast, mood, etc, are much more important.

F/128 on a FF sensor is only ~ 1MP recorded (median/green wavelengths) and it is not something I would do or generally recommend... but maybe that is sufficient for you (Paul) because you are only going to put it online at 1024px long edge (<1MP); or maybe you don't actually care about/need much resolution at all.
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Different words saying much the same thing. if an image is diffraction limited it becomes impossible to distinguish the difference between the diffracted point of focus, and a point that is blurred by being out of focus by the same amount. it has the effect of producing an evenness of focus over a far greater depth. but at a lower frequency.

This is largely indistinguishable on large format where extremely small apertures can be used with little loss of sharpness. they just seem evenly sharp all over.
 
AndrewFlannigan said:
It occurs to me that if Ralph Waldo Emerson had been a keen photographer he might have rephased his famous aphorism as "sharpness is the hobgoblin of obsessive photographers, adored by self described artists and those who prefer a boring image to an interesting one".

I shall now exit smartly to the left... :exit:
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It's a shame we've got down to sniping now. There's plenty of well known (and well paid) 'photographic artists' who intentionally produce the most highly detailed images because it adds to their art, as well as those who choose to degrade their images for the same reason.
 
sk66 said:
Diffraction does not relate to a specific physical aperture diameter.
Diffraction is due to a light path obstruction which is the entrance pupil; which is defined by f#. The entrance pupil/f# is the effective size of the physical aperture restriction as magnified by the objective element(s). And all lenses will project the same size airy disks at the image plane when set to the same f# (assuming no additional optical errors).

When the airy disks are smaller than a pixel they are not resolved (individually), when they are the same size as a pixel they are resolved perfectly, when they exceed the size of a pixel contrast decreases, and when they exceed ~ 2x the size of a pixel recorded resolution decreases... if they exceed the size of a pixel by 4x the recoded resolution will be less than when at 2x.

Now; whether you will see these effect, or if you even care, is another matter...

Here's a technical paper on diffraction: Do sensors outresolve lenses' capabilities?

Edit: it just occurred to me that your 3mm limit for an 8x10 print is probably the 30micron airy disk (FF CoC limit) magnified/enlarged to .3mm in the print. FWIW, the CoC limit(s) are quite arguably insufficient for modern usage (digital display)... and it's arguable that it was never actually sufficient (I calculated that it is based on ~ 20/40 vision).
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Steven is right. Any lens used on the same format camera will be diffraction limited at high f/numbers, let's say f/16, and the effect will be the same regardless of focal length (or indeed, of lens quality or cost). However, diffraction is affected by format (sensor size) and smaller formats are hit sooner, ie at lower f/numbers. It follows the crop-factor, so an APS-C camera (1.5-1.6x crop factor) will suffer the same diffraction at f/11-ish and on M4/3 (2x) that'll be f/8.
 
Some cameras now have algorithms in their firmware that deconstruct the effects of diffraction so as to limit its effect. I have not seen any way. To do a comparison of even seen one anywhere . So I have no idea how effective this is in practice. But I expect it is similar to similar efforts in Photoshop to debase.
 
Terrywoodenpic said:
Some cameras now have algorithms in their firmware that deconstruct the effects of diffraction so as to limit its effect. I have not seen any way. To do a comparison of even seen one anywhere . So I have no idea how effective this is in practice. But I expect it is similar to similar efforts in Photoshop to debase.
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Fujifilm Diffraction Correction? No miracle cure and it doesn't seem to have caught on. I think you're better off with a bit of DIY local sharpening.

But this is something that AI should be able to get to grips with, so likely to appear in smartphones if it hasn't already. Small sensors get clobbered by diffraction even at everyday f/numbers and some cameras use neutral density filters rather than close the aperture down further.
 
HoppyUK said:
Fujifilm Diffraction Correction? No miracle cure and it doesn't seem to have caught on. I think you're better off with a bit of DIY local sharpening.
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Canon also offers it in their DPP software, and also in some newer bodies as part of lens corrections (I've read). And Sony had it as part of their Bionz X processor about 10 yrs ago. It's probably very common as part of lens correction profiles I would guess. AFAIK, diffraction correction is all just versions of sharpening; primarily deconvolution sharpening... and it has the same potential negative side effects that sharpening in post has; because that is what it is.

What is not recorded cannot be recovered; at best it can be artificially replaced. Diffraction does not only cause a loss of contrast/resolution. It also reduces the sensor generated SNR, color accuracy, and tonality (individual values w/in the DR). And if the smaller aperture also causes recording less light (higher ISO), then that will compound these effects significantly. That's a whole lot of lost information to ask software to make its' best guess about... why would anybody resort to that if they don't have to?
 
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