Canon 18-135mm f/36!

[Abitconfused]

This lens stops down to f/36. Is there any practical use for so small an aperture? True, I have heard of f/64 but I have not seen it. What am I missing here? I would have believed the more common f/22 would be sufficien for depth of field and/or limiting light.

[Stagecoach]

I suppose it all depends upon what DoF you want to achieve Ed.

Take the example of shooting at 18mm through to 135mm as close as you can get to a subject and there's a difference in DoF between f/22 and f/36, it may mean you achieving the result you want or not achieving it.

Then of course diffraction and its impact on your result has to be considered.

One use could be to assist in slowing the shutter speed for those smooth water affects when you can't wait for the light to drop more and have no filters with you.

But personally I can never think of a time I have stopped a lens to it's minimum other than testing the results of a macro.

[Manfred M]

The group that Ansel Adams was a founding member of was called Group f/64, as this is the aperture that they commonly shot at. Don't forget that they used a view camera (4" x 5" negatives and larger). He used 12" (300mm) lenses in a lot of his work. Remember that the aperture number is nothing more than the ratio of the focal length to the diameter of the entrance pupil.

As Grahame has mentioned, the main issue of using smaller shooting apertures are the diffraction effect caused when the light hits the edges of the aperture blades; the smaller the blade opening the more pronounced the effect of diffraction. I rarely shoot stopped all the way down for this reason and will opt for a neutral density filter to let me shoot at a larger aperture in those extreme shooting situations.

[rpcrowe]

I might, and I stress "might", try that f/stop in shooting night shots if I wanted the specular lights within my frame to be recorded as star bursts. This image was shot at f/14 to slow down the shutter speed and also to record the lights along the seawall as starbursts - if I had an f/36 on my lens, I "might" have experimented with that f/stop. I say "might" because I didn't shoot this shot with the smallest aperture of my lens...



I don't generally shoot at a much smaller f/stop than f/16 because (as Manfred & Grahame remarked) of diffraction... I mostly shoot landscapes around f/8 or f/11 depending on the focal length I am using...

When I shot with a 5 x 7 inch studio camera, I had no diffraction problems with f/22 or even f/32 since the aperture of f/22 or f/32 was large enough that it did not cause diffraction... I shot portraits at f/16 or so because for "official portraits" everything had to be sharp. I used a split back for the portrait work which gave me two portraits, side by side on a 5 inch x 7 inch piece of cut film...

[Black Pearl]

On a slightly different tack - if you have a few minutes to spare run a test and view the images as the aperture is set smaller. The results from the very small apertures are likely to be quite shocking....even without the need to use high magnification when viewing them.

[William W]

This lens stops down to f/36. Is there any practical use for so small an aperture?

Knocks out the need for an extra stop or two when the shot requires an ND Filter . . . or the need for an ND Filter.

WW

[DanK]

The group that Ansel Adams was a founding member of was called Group f/64, as this is the aperture that they commonly shot at. Don't forget that they used a view camera (4" x 5" negatives and larger). He used 12" (300mm) lenses in a lot of his work. Remember that the aperture number is nothing more than the ratio of the focal length to the diameter of the entrance pupil.

As Grahame has mentioned, the main issue of using smaller shooting apertures are the diffraction effect caused when the light hits the edges of the aperture blades; the smaller the blade opening the more pronounced the effect of diffraction. I rarely shoot stopped all the way down for this reason and will opt for a neutral density filter to let me shoot at a larger aperture in those extreme shooting situations.

This issue came up in a thread 6 years ago. I'll repeat here what I wrote there: I know very little about this other than what I have read on the tutorials pages here and a few other sites. However, here is a relevant quote about diffraction from the tutorial pages, https://www.cambridgeincolour.com/tu...hotography.htm

Technical Note: Independence of Focal Length
Since the physical size of an aperture is larger for telephoto lenses (f/4 has a 50 mm diameter at 200 mm, but only a 25 mm diameter at 100 mm), why doesn't the airy disk become smaller? This is because longer focal lengths also cause light to travel further before hitting the camera sensor -- thus increasing the distance over which the airy disk can continue to diverge. The competing effects of larger aperture and longer focal length therefore cancel, leaving only the f-number as being important (which describes focal length relative to aperture size).

The advantage Adams had, if I understand correctly, was the first point in Manfred's post: the size of the film he used.

[george013]

This issue came up in a thread 6 years ago. I'll repeat here what I wrote there: I know very little about this other than what I have read on the tutorials pages here and a few other sites. However, here is a relevant quote about diffraction from the tutorial pages, https://www.cambridgeincolour.com/tu...hotography.htm



The advantage Adams had, if I understand correctly, was the first point in Manfred's post: the size of the film he used.

I think it's incorrect. Diffraction is not related to the aperture diameter. It's related to the angle of the light cone aperture-image distance. At infinity this is the focal length. That angle doesn't change when the focal length changes with the same f-number.
That Adams and his fellows didn't have problems with diffraction is based on the film format. With a taller format a bigger coc can be used.
For a 4x5 film a coc of 0.1 is used, for a ff 0.03 and for a dx 0.02mm.
My thoughts.

George

[Stagecoach]

I think it's incorrect. Diffraction is not related to the aperture diameter.

I also think your above statement is incorrect and misleading George.

Since I picked up a camera and started serious photography everything I read and hear tells me the smaller the aperture I use the more diffraction I will get. If diffraction is not related to the aperture diameter, why is it then that when I alter that diameter my diffraction will alter as well?

Aperture, definition - an opening, hole, or gap.

Related to, definition - being connected either logically or causally or by shared characteristics

There is a difference in meaning between the words related and what I suspect you are trying to raise, which is reason/cause.

[george013]

I also think your above statement is incorrect and misleading George.

Since I picked up a camera and started serious photography everything I read and hear tells me the smaller the aperture I use the more diffraction I will get. If diffraction is not related to the aperture diameter, why is it then that when I alter that diameter my diffraction will alter as well?

Aperture, definition - an opening, hole, or gap.

Related to, definition - being connected either logically or causally or by shared characteristics

There is a difference in meaning between the words related and what I suspect you are trying to raise, which is reason/cause.

Please don't start again. Look for the definitions of the Airy disk and diffraction on Wikipedia or in other books. It's dependent on the ratio aperture diameter and image distance. Read and try to understand. If you change focal length with a equal f-number, you're changing aperture diameter too. The only constant is the top angle of the light cone aperture diameter-image distance. See Angular aperture https://en.wikipedia.org/wiki/Angular_aperture

Light passing your door or window is diffracted too. It's only invisible. In a lens system the light is converged to a central point and that's where those light beams passing the material of the aperture directly influence each other. They come together in that point. See light as a beam with a width. The sharper that angle, the longer the road they can influence each other.

Diffraction in photography always exist. The question is only when it becomes visible. The answer is like sharpness: at a certain enlargement and viewing distance.

You might also search for diffraction and macro. There the f-number is replaced with the effective f-number. That's only a correction of the simplification using the f-number with diffraction. It should be image distance. The effective f-number is the ratio aperture diameter- image distance. With a magnification of 1 a difference of 100%.

As said before, just my thoughts.

George

[William W]

. . . There is a difference in meaning between the words related and what I suspect you are trying to raise, which is reason/cause.

Yep, nailed in one, I suspect.

WW

[Stagecoach]

Please don't start again. Look for the definitions of the Airy disk and diffraction on Wikipedia or in other books. It's dependent on the ratio aperture diameter and image distance. Read and try to understand. If you change focal length with a equal f-number, you're changing aperture diameter too. The only constant is the top angle of the light cone aperture diameter-image distance. See Angular aperture https://en.wikipedia.org/wiki/Angular_aperture

Light passing your door or window is diffracted too. It's only invisible. In a lens system the light is converged to a central point and that's where those light beams passing the material of the aperture directly influence each other. They come together in that point. See light as a beam with a width. The sharper that angle, the longer the road they can influence each other.

Diffraction in photography always exist. The question is only when it becomes visible. The answer is like sharpness: at a certain enlargement and viewing distance.

You might also search for diffraction and macro. There the f-number is replaced with the effective f-number. That's only a correction of the simplification using the f-number with diffraction. It should be image distance. The effective f-number is the ratio aperture diameter- image distance. With a magnification of 1 a difference of 100%.

As said before, just my thoughts.

George

George,

What is it that I am starting again? I have simply pointed out that your use of words is incorrect and misleading.

My post has absolutely nothing to do with the reason/cause of diffraction.

[george013]

George,

What is it that I am starting again? I have simply pointed out that your use of words is incorrect and misleading.

My post has absolutely nothing to do with the reason/cause of diffraction.

You continue on the person. Not on the subject.
Unless we continue with the subject I stop. I've said what I wanted to say.

George

[William W]

{ASIDE}

You continue on the person. Not on the subject.
Unless we continue with the subject I stop. I've said what I wanted to say.

Hi George,

Just something that you might PLEASE consider:

If someone draws attention to the incorrect use of a word or words, that is not necessarily attacking the person who used the incorrect word.

We need to identify the reason for a comment.

The REASON for Grahame's comment is to clearly to correct the misleading information contained in the words that you wrote.

Grahame's comment was clearly NOT a comment on you.

There were TWO reasons why Graham made his comment

- firstly it was to highlight to all readers that there is an error of fact the error in the sentence " Diffraction is not related to the aperture diameter."

- secondly Grahame alluded to his interpretation of what he thought that you meant: "There is a difference in meaning between the words related and what I suspect you are trying to raise, which is reason/cause."

Personally, I do read mostly all of your commentary and I do sincerely appreciate your passion for Photography and your detail and effort to ferreting out information and to acquire a deep technical understanding of Photography: so having stated that . . . please think about this below because it is written with sincerity and the sole purpose of assisting you:

My guess is that written English is not you first written language and sometimes you might not use the precise or the correct word.

That can become a problem when it leads to confusion, as it did above.

Mistakes like that happen to people who are highly educated and extremely skilled in writing - so you are not alone.

For example I proof read all my Wife's reports before they are sent. She has been in practice for over 25 years and I still pick up on grammatical and nuance of meaning errors and it is really important to have a proofreader (or two) when documents might be challenged legally.

My wife does not think that I am attacking her or her writing skill when I point out an error in her script, but she is appreciative that the error is found, so she can be assured that the meaning of what she wrote is both precise and also accurate in fact.

Grahame was simply pointing out to all the readers that George probably meant something different to what he wrote, simply because George used an imprecise word. Graham was not attacking George, simply correcting an error of fact.

I think that it would be more gracious and also more useful if George would be simply thankful that Grahame took the time to explain that error to him.

WW

[Tronhard]

One of the greatest reasons for misunderstanding, and even conflict when none is intended, is the nature of semantics: simply how we use or understand words in communication. In situations where one is getting into detailed debates, the PRECISE meaning of words becomes extremely significant to the conversation. To question the language used is not to attack the person per se, it is to try to clarify and remove any confusion.

If I may offer a light-hearted example (hopefully not to offend):

A man goes to his doctor and tells him he wants to be castrated. The shocked doctor tries to persuade him to the contrary, but he is adamant. Having signed all the forms he is operated on. In the recovery room he wakes to find another fellow beside him. He asks his companion what operation he had, and the chap responds that he had a vasectomy. At which point the old chap exclaimed "THAT's the word!"

To offer my two cents' worth on this original subject, or rather Prof Marc LeVoy from his series "Lectures on Digital Photography" I would think it is worth while reading his slides 36-40 from this lecture:
https://drive.google.com/file/d/0B6w...VpWThHM0U/view
or
Watch his lecture at this link:
https://sites.google.com/site/marcle...cture4-30mar16
Start at time 43m:38s for his explanation on diffraction and its implication with lens apertures.

[Tronhard]

{ASIDE}
For example I proof read all my Wife's reports before they are sent. She has been in practice for over 25 years and I still pick up on grammatical and nuance of meaning errors and it is really important to have a proofreader (or two) when documents might be challenged legally.

My wife does not think that I am attacking her or her writing skill when I point out an error in her script, but she is appreciative that the error is found, so she can be assured that the meaning of what she wrote is both precise and also accurate in fact.

WW

Bill I know what you mean. My other third (she's too short to be my other half! ) is an academic, and absolutely a killer editor. Prior to putting it out, I give her my own material to check through. She is absolutely anal in targeting and questioning any inconsistency in grammar, context or semantics. It is easy to become defensive about such things, especially we feel an emotional connection to our editor. That said, I know she is being a professional and making sure I do myself justice.