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Valued Contributor
Posts: 370
Registered: ‎12-24-2013

Mysterious index mark on focal length zoom ring?

[ Edited ]

I own 12 different EF and EF-S Zoom lenses. 5 of them have a mysterious index mark on focal length zoom ring as shown in the photos below.  The 24-105mm USM also has a little white dot. I circled the markings in Red.

 

My 7 other Zoom lenses have no markings at all other than the focal lengths. 

 

 Clipboard01.jpg

 

  

Mike Sowsun
S110, SL1, 5D Mk III
Valued Contributor
Posts: 370
Registered: ‎12-24-2013

Re: Mysterious index mark on focal length zoom ring?

[ Edited ]

I think I figured it out.... Looking at the photos all together it sudden occurred to me that the little white index is at the end of the focal length travel and it is there just because the numbers at the end of the travel don't line up with the focal length index. I'm guessing it's just the way Canon wanted to space out the numbers on the zoom ring.

 

BUT.... It still doesn't explain the little white dot beside 35mm on the 24-105 USM.

Mike Sowsun
S110, SL1, 5D Mk III
Valued Contributor
Posts: 370
Registered: ‎12-24-2013

Re: Mysterious index mark on focal length zoom ring?

[ Edited ]

After some Google research I found out that the white dot indicates the 28mm focal length and that there just wasn't enough room for "28" on the lens barrel.

Mystery solved!

 

The Ken Rockwell review spelled it out quite clearly:

 

 "The range from 24 - 50mm is squeezed into half the space, and the range from 24 - 35mm is only about 1mm along the zoom ring: the distance between the bar to the right of 24mm to the dot to the left of 35mm! These focal lengths are so close that Canon couldn't fit the numbers on the ring so they had to put those little marks there instead! This makes it very difficult to select exact settings at the wide end".

Mike Sowsun
S110, SL1, 5D Mk III
Esteemed Contributor
Posts: 3,936
Registered: ‎06-25-2014

Re: Mysterious index mark on focal length zoom ring?


MikeSowsun wrote:

I think I figured it out.... Looking at the photos all together it sudden occurred to me that the little white index is at the end of the focal length travel and it is there just because the numbers at the end of the travel don't line up with the focal length index. I'm guessing it's just the way Canon wanted to space out the numbers on the zoom ring.

 

BUT.... It still doesn't explain the little white dot beside 35mm on the 24-105 USM.


I was going to answer along those lines, but you beat me to it. The extra mark is undoubtedly a pointer to the number that would have been above the line if they could have fit it in.

 

So instead I'll venture a wild stab at an answer to your question about the dot on the 24-105. Given the placement of the dot, and given the fact that it's not uncommon to use the 24-105 on an APS-C camera, I suggest that it indicates the point (approx. 32mm) at which the lens subtends the angle of view of the human eye when used on an APS-C camera (i.e., the focal length whose "full-frame equivalent" is 50 mm). I told you it was a wild guess; but it's my guess, and I'm sticking with it!

 

Actually, I suspect that the question is answered in the lens's user manual, but I'm too lazy to look it up.

Bob
Boston, Massachusetts USA
Reputable Contributor
Posts: 914
Registered: ‎02-06-2013

Re: Mysterious index mark on focal length zoom ring?

The flag is easy, it marks the actual location of the number representing the FL versus where the number is printed.

 

The dot, while debatable, is where 28 should be.

================================================
Diverhank's photos on Flickr
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Posts: 8,476
Registered: ‎12-07-2012

Re: Mysterious index mark on focal length zoom ring?

"The flag is easy, it marks the actual location of the number representing the FL versus where the number is printed."

 

This is correct as you notice you can not move past the 'flag' mark.

A lot less stuff for 2018 but still a lot of Canon stuff. Along with, a lot of other stuff.
Valued Contributor
Posts: 370
Registered: ‎12-24-2013

Re: Mysterious index mark on focal length zoom ring?


RobertTheFat wrote:

 

Actually, I suspect that the question is answered in the lens's user manual, but I'm too lazy to look it up.


I looked in a couple of different lens manuals and I could not find any info on the marks. 

Mike Sowsun
S110, SL1, 5D Mk III
Esteemed Contributor
Posts: 2,114
Registered: ‎02-17-2016

Re: Mysterious index mark on focal length zoom ring?

If it is like my 15-85, the dot is where the lens is at its minimum length, and where it should be "parked".

Esteemed Contributor
Posts: 3,936
Registered: ‎06-25-2014

Re: Mysterious index mark on focal length zoom ring?


kvbarkley wrote:

If it is like my 15-85, the dot is where the lens is at its minimum length, and where it should be "parked".


The 24-105 is at its minimum length at 24 mm and is normally parked there (at least by me). So far, I still prefer my original guess.

 

Out of curiosity, where is the dot on the 15-85? If it's at around 32, it doesn't contradict my explanation.

Bob
Boston, Massachusetts USA
Esteemed Contributor
Posts: 3,936
Registered: ‎06-25-2014

Re: Mysterious index mark on focal length zoom ring?


diverhank wrote:

The flag is easy, it marks the actual location of the number representing the FL versus where the number is printed.

 

The dot, while debatable, is where 28 should be.


How did you determine that? By taking a picture with the lens set on the dot and having the Exif tell you it was at 28? It you're right, maybe the dot is aimed at users who upgraded from the earlier EF 28-105mm f/4.5-5.6. But that's at least as far-fetched as my other guess.

Bob
Boston, Massachusetts USA
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