Focal Length problem with EF 70-300mm f/4-5.6 IS II USM - shows up as 267mm

[MickKazik]

Hi everyone, I just received my new EF 70-300mm f/4-5.6 IS II USM and I'm battling a big issue.

On its long end (supposedly 300mm), the zoom ring rotates all the way but lens indicate 267mm in the photo data (Canon 200D). Since it has got an APS-C sensor, the display on the lens should indicate 480mm. In reality the marker on the lens is lined up at 300mm but on the built in lens display if falls a quarter of an inch short.

On my ancient 1D mk II n the indicator on the display should point to 390mm but falls short again. 

In both cases only the shorter focal length of 70mm is lined up properly and also shows as 70mm in photo info.

Both in-camera info and Lightroom EXIF data indicate incorrect values. Basicaly, the longer you extend, the bigger the discrepancy. Example:

70mm = 70mm

100mm = 94mm

135mm = 126mm

200mm = 176mm

300mm = 267mm

Do you think I can do anything with it or did I get a faulty piece?

Thanks in advance!

[wq9nsc]

Mick,

Glad to hear that you are returning it.  It does sound like it was probably a defective return and sometimes retail distributors just put a returned item back into distribution even though they shouldn't.  I buy a fair amount through Amazon and twice I have received "new" items that clearly weren't but at least the return process was very easy.

I haven't done extensive testing but in a quick test with my Canon EF 70-200 f2.8 and EF 24-70 f2.8 lenses, both indicate the correct focal length at both zoom extremes regardless of focus distance from minimum focus distance to infinity.  I suspect that the zoom mechanism feeds the commanded focal length data which may not be exact for the actual focus length but the numbers will be invariant with respect to focus distance. 

In reality, the true focal length (you could measure in terms of what is actually in frame at a specified focal length) will vary somewhat due to tolerances and "focus breathing" but the data reported should be the same as it is with these two lenses I tested.  I use mostly prime glass and these are the only two zoom lenses I own but I suspect that other Canon zooms (including non L types) will report data the same way based upon a mechanical control rather than an optical result.

Rodger

[ebiggs1]

"... a quick test with my Canon EF 70-200 f2.8 and EF 24-70 f2.8 lenses, both indicate the correct focal length at both zoom extremes regardless of focus distance from minimum focus distance to infinity."

And how are you determining that they are reporting true?  My very loved Sigma 150-600mm f/5-6.3 DG OS HSM Sports Lens reports to LR that it is at 600mm. Yet DXO measured the actual FL of that lens to be 577mm. 600mm isn't possible. My, no longer with me, expensive, Nikkor 300mm f4 reported to LR it was 300mm. But again DXO measured the actual FL of the lens to be 303mm. So, it is not just a zoom lens phenomenon.

LR simply reads the EXIF data supplied by the lens to the camera. All I am trying to say here is LR or any EXIF reader is not an accurate way to now the true FL. It can be and it might not be.

[wq9nsc]

Ernie,

I think you missed part of my response.  I was stating what the lens REPORTS in terms of EXIF data for the two lenses I checked and noted later that the true focal length is likely slightly different.  The OP started this thread based upon the EXIF data not matching where the lens control ring was set.

I suspect very few lenses, including L series primes, would consistently measure within 1mm of stated focal length because even a very slight difference in mount or sensor placement will impact TRUE focal length.  But the electronics should report the stated focal length even though that isn't the perfectly accurate focal length.

A lens that doesn't report the stated focal length range to the camera has an issue.

Rodger

[ebiggs1]

I understand but at the very first of this issue, if you, the OP, anybody, is using LR or EXIF to verify your lens is actually what it claims, you can't do that with any expectation of accuracy. And that is exactly what he noticed and asked. Correct?

Also I have no way of knowing any new posters level of photographic knowledge. Most of the regulars here are advanced but lots of new posters are not. That is where you begin. The first screen shot was apparently a macro shot so focus breathing had to be examined.  He also was using EXIF data to confirm the FL. That was the start but now we all know differently and believe the lens is truly faulty and needs to be returned.

Perhaps sloppily but everyone is trying to help. Even me! 

[MickKazik]

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@wq9nsc wrote:

Mick,

Glad to hear that you are returning it.  It does sound like it was probably a defective return and sometimes retail distributors just put a returned item back into distribution even though they shouldn't.  I buy a fair amount through Amazon and twice I have received "new" items that clearly weren't but at least the return process was very easy.

I haven't done extensive testing but in a quick test with my Canon EF 70-200 f2.8 and EF 24-70 f2.8 lenses, both indicate the correct focal length at both zoom extremes regardless of focus distance from minimum focus distance to infinity.  I suspect that the zoom mechanism feeds the commanded focal length data which may not be exact for the actual focus length but the numbers will be invariant with respect to focus distance. 

Rodger

Hi Rodger! Thanks a lot for your response and testing done. You understood the problem prefectly, I wish there was some easy solution to it, re-calibrating of some sorts. There is no problem with returning it though, it will go back tomorrow. 

Nevertheless, I was astounded by the lack of of info online about the exact issue with this lens. Surely I'm not the only one with this kind of defect (statement in advance: no it is not focus breathing). Thanks again.

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[Waddizzle]

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@MickKazik wrote:

Hello Ricky, thank you for your reply. 

I was really hoping this was the case but unfortunately it's not. Took multiple shots at various focus ranges and it's still the same. It seems like the actual physical zoom isn't calibrated with the digital read outs. I am attaching photographs for reference.

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I would ignore this "equivalent view" display.  It really serves no purpose, and it only confuses people.  The EXIF data is correct because it is reporting the physical characteristics of the lens.  

This display is compensating for crop factor in the sensor, and should never be reported in the EXIF data.  If you crop an image in post, should that also be reported in the EXIF data?  I would hope not.

[jrhoffman75]

Does anyone here, besides Mick and myself, actually own the lens?

The lens reports 70-300 on my 1D X and 112 to 480 (stating 35mm equivalent) on my wife’s Rebel T6s crop sensor.

Lens appears to be defective.

[ebiggs1]

"Lens appears to be defective."

Agree, it needs to go back, today!

[Waddizzle]

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@jrhoffman75 wrote:
Does anyone here, besides Mick and myself, actually own the lens?

The lens reports 70-300 on my 1D X and 112 to 480 (stating 35mm equivalent) on my wife’s Rebel T6s crop sensor.

Lens appears to be defective.

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I agree.  I think the lens is defective, too.  The very first thing I advised was to return it for a full refund.  I learned that it is a used lens, and added the caveat to find a new vendor, no exchanges.

[kvbarkley]

I do, it reports 112-480 on its LCD on my Rebel T6S. And the EXIF shows 300 mm