Shooting at an unmarked focal length

This is probably a stupid question and I've searched the forums for an answer, but nothing found. Perhaps I'm not using the correct terminology.

At the weekend I wanted to make some test shots between 2 lenses @ 75mm. On one lens there was a 75mm mark but on the other there was a 70mm and then 105mm. I had to make a guess as to where the 75mm mark was and the open the pic in Adobe Bridge to see the focal length I'd just shot.

Is there a feature on my 5D MkII to show what focal length the camera is sitting at? Even if I press the Info button for an image there is no mention of which focal length the image was shot at (or not that I could find).

Thanks for any help.

Not in the camera, but later in a computer you can see the full Exif. Most lenses report focal length, but not all of them. However, the reported number isn't always accurate - compare a Canon 50 mm. prime and a Sigma 50 mm. and there may be a slight difference in image size.

Pentax would allow you to see the focal length prior to taking a shot.

egordon99 wrote in post #10276744
Pentax would allow you to see the focal length prior to taking a shot.

But who would Admit to owning one

LONDON808 wrote in post #10278849
But who would Admit to owning one

I owned TWO Pentax DSLRs prior to joining the Canon clan. Pentax makes some nice lenses (especially primes) and their bodies are catching up with Canikon.

egordon99 wrote in post #10278906


I owned TWO Pentax DSLRs prior to joining the Canon clan. Pentax makes some nice lenses (especially primes) and their bodies are catching up with Canikon.

They make great glass but there bodies need a lot of work - they feel like toys IMO who knows in a few years with sone serious r and d they could be a lot better

Cornelius wrote in post #10275913
This is probably a stupid question and I've searched the forums for an answer, but nothing found. Perhaps I'm not using the correct terminology.

At the weekend I wanted to make some test shots between 2 lenses @ 75mm. On one lens there was a 75mm mark but on the other there was a 70mm and then 105mm. I had to make a guess as to where the 75mm mark was and the open the pic in Adobe Bridge to see the focal length I'd just shot.

Is there a feature on my 5D MkII to show what focal length the camera is sitting at? Even if I press the Info button for an image there is no mention of which focal length the image was shot at (or not that I could find).

Thanks for any help.

All lenses that will fit on a particular camera and that will allow you to frame the scene the same way will be set at precisely the same focal length when framing the scene the same way. The exact focal length used for such a test would be inconsequential as long as both were the same.

You could put two objects into the scene that would be at each end of the image with one lens and then adjust the other lens to have the objects at the same place in the viewfinder as the first.

The focal length markings - and even the reported focal lengths - of various lenses are only approximate. Manufacturers tend to round off the stated focal length (or focal length range in the case of zoom lenses) values.

In addition, focal lengths are measured only at infinity focus settings. Thus, if you are focused closer than infinity, two different design lenses that are supposed to be the same focal length could provide different fields of view when focused on a relatively close subject while providing much closer fields of view when focused on distant subjects.

SkipD wrote in post #10279920
All lenses that will fit on a particular camera and that will allow you to frame the scene the same way will be set at precisely the same focal length when framing the scene the same way. The exact focal length used for such a test would be inconsequential as long as both were the same.

You could put two objects into the scene that would be at each end of the image with one lens and then adjust the other lens to have the objects at the same place in the viewfinder as the first.

The focal length markings - and even the reported focal lengths - of various lenses are only approximate. Manufacturers tend to round off the stated focal length (or focal length range in the case of zoom lenses) values.

In addition, focal lengths are measured only at infinity focus settings. Thus, if you are focused closer than infinity, two different design lenses that are supposed to be the same focal length could provide different fields of view when focused on a relatively close subject while providing much closer fields of view when focused on distant subjects.

Thanks for that information!

OK, so let's take the "lens comparison" out of the discussion and let's just say I want to shoot at an unmarked focal length i.e. 75mm. As it's not marked on my 24-105mm lens, am I correct in saying that I have to guess what length I'm shooting at out in the field and the only way to know for sure is by downloading the images to my Mac and reading the EXIF data?

Well, one can use the Magic Lantern firmware to give you access to extra shooting information, like the exact FL, and even the near/far depth of field. It hasn't been updated yet, though.

Cornelius wrote in post #10280680
Thanks for that information!

OK, so let's take the "lens comparison" out of the discussion and let's just say I want to shoot at an unmarked focal length i.e. 75mm. As it's not marked on my 24-105mm lens, am I correct in saying that I have to guess what length I'm shooting at out in the field and the only way to know for sure is by downloading the images to my Mac and reading the EXIF data?

Yes, that's true. But most people are more concerned about getting the subject framed as they want it and don't really care what the exact FL is.

Cornelius wrote in post #10280680
Thanks for that information!

OK, so let's take the "lens comparison" out of the discussion and let's just say I want to shoot at an unmarked focal length i.e. 75mm. As it's not marked on my 24-105mm lens, am I correct in saying that I have to guess what length I'm shooting at out in the field and the only way to know for sure is by downloading the images to my Mac and reading the EXIF data?

tzalman wrote in post #10280843
Yes, that true. But most people are more concerned about getting the subject framed as they want it and don't really care what the exact FL is.

I agree 100% with Elie.

I think you may find some very interesting reading in a tutorial that I and others put together on the subject of controlling perspective. There are lots of photos illustrating the points we made. Please read our "sticky" (now found in the General Photography Talk forum) tutorial titled Perspective Control in Images - Focal Length or Distance?.

Thanks guys.
Don't get me wrong. I usually don't even check what focal length I'm at and try to concentrate on the composition. I don't wake up and think "OK. Today is 75mm day!" It was more out of curiosity more than anything else.

I was checking that post of yours yesterday, Skip. It's a really good read.

Cornelius wrote in post #10281009
I don't wake up and think "OK. Today is 75mm day!"

I actually do say "Today is 30mm and 85mm day!"

I've been taking my primes out a lot as the 24-70L is a big heavy beast and the primes have better IQ anyway (yep, even without the red ring )