topic Re: Mysterious index mark on focal length zoom ring? in EF & RF Lenses

Mysterious index mark on focal length zoom ring?

MikeSowsun — Wed, 27 Dec 2017 18:45:34 GMT

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.

Re: Mysterious index mark on focal length zoom ring?

MikeSowsun — Wed, 27 Dec 2017 18:25:06 GMT

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.

Re: Mysterious index mark on focal length zoom ring?

MikeSowsun — Wed, 27 Dec 2017 18:50:34 GMT

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".

Re: Mysterious index mark on focal length zoom ring?

RobertTheFat — Wed, 27 Dec 2017 19:19:54 GMT

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.

Re: Mysterious index mark on focal length zoom ring?

diverhank — Wed, 27 Dec 2017 19:55:53 GMT

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.

Re: Mysterious index mark on focal length zoom ring?

ebiggs1 — Wed, 27 Dec 2017 21:33:37 GMT

"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.

Re: Mysterious index mark on focal length zoom ring?

MikeSowsun — Wed, 27 Dec 2017 23:19:27 GMT

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.

Re: Mysterious index mark on focal length zoom ring?

kvbarkley — Sat, 30 Dec 2017 00:24:05 GMT

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

Re: Mysterious index mark on focal length zoom ring?

RobertTheFat — Sat, 30 Dec 2017 06:24:18 GMT

@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.

Re: Mysterious index mark on focal length zoom ring?

RobertTheFat — Sat, 30 Dec 2017 06:37:54 GMT

@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.

Re: Mysterious index mark on focal length zoom ring?

MikeSowsun — Sat, 30 Dec 2017 14:50:34 GMT

Yes, on the EF 24-105mm USM, the EXIF data does confirm that the dot corresponds to 28mm .

Re: Mysterious index mark on focal length zoom ring?

RobertTheFat — Sat, 30 Dec 2017 15:42:08 GMT

@MikeSowsun wrote:
Yes, on the EF 24-105mm USM, the EXIF data does confirm that the dot corresponds to 28mm .

Back in the film days, 28mm was a common focal length for a wide-angle prime. (I still have one for my Nikon F-2.) Conceivably that's why Canon thinks it's worth pointing out where that is on the 24-105.

I see that on my 16-35 f/4, the indicated "in between" values are 20, 24, and 28. Maybe Canon uses the dot whenever they want to mark the position of a popular focal length but don't have room for the number.

Re: Mysterious index mark on focal length zoom ring?

diverhank — Sun, 31 Dec 2017 01:16:41 GMT

@RobertTheFat wrote:
@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.

That was my guess :). I have no proof but if you take a look at other pictures the OP posted, 28mm is everywhere...Canon deemed it important to mark it. On my 24-70mm f/2.8L II, it was marked 24 (flag), 28, 35, 50, 70.