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!

[rs-eos]

This can indeed occur with zoom lenses and even primes I believe.  And it's driven by focus.  As you focus on nearer or further subjects, the focal length will change a bit.

On your lens, set the focal length to 300mm, then focus on something very distant.  Metadata for that image should be much closer, if not at, 300mm.  But then at that same focal length, focus to a closer subject.  You'll find the actual focal length will be shorter.

You can find further details by also looking into focus breathing.

[MickKazik]

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.

[ebiggs1]

As Ricky said.......

"You can find further details by also looking into focus breathing."

I still think you are a victim of focus breathing. What the lens indicates on its zoom rings and the true FL can be and is different a lot of the time.

Your screen shot looks like you are very close to the subject. The lens, not only bottom end lenses, yours, but some high end lenses, change their FL quite a bit to achieve focus. A notorious high end lens was the Nikkor 70-200mm which could only get around 125mm at close focus although the zoom ring indicated 200mm. And that was a two thousand dollar plus lens.

This effect is common to all zoom lenses, and is a necessary compromise in the design process. It just seems some do a better job than others.

It looks like you may be a candidate for a true macro lens. The 70-300mm really isn't at its forte doing that work.

If you shoot something at the infinity distance at 300mm what does LR report? Again it may not be exactly 300mm as the advertising department will sometimes be optimistic when naming and making claims about a product

[MickKazik]

Hey 'ebigs', thanks for your insight. It's certainly good to know that going forward, I wasn't even aware of it but unfortunatelly it doesn't seem this to be the case here.

The photos provided were only to indicate the issue - not my intended subject / purpose of photography. In fact I don't do any macro photography. 

As you can see from the photos, the markings are simply not aligned and no matter what you do (whether it's close ups, shooting subjects that are far or infinity), the max focal length doesn't go past 267mm. Ever. 

Originally I thought the fault may only be restricted to the built-in display (it's there for a reason) but metadata is in line with what the display indicates.

• I checked online and 480mm marking on the display (when on an APS-C camera) when at 300mm should be aligned.- it is not. 
• Same on APS-H camera - 390mm marking isn't aligned which then translates to 267mm in metadata, no matter where you focus. It just doesn't go past that.
• I also checked it on my Fuji XT3 with Fringer adapter and again, it isn't aligned and max focal length comes up as 256mm - no matter where you point it (photo attached).

The lens was bought on Amazon and in 'excellent condition'. I am suspecting it could've been a return due to the same issue that was never resolved.

Any other ideas taking into account all of the above would be much appreciated.

[MickKazik]

I must add that I read / watched tons of reviews of this lens with hundereds of photos imported to Lightroom indicating 300mm at it's longest end. This lens doesn't go past 267mm no matter what you do with it. 

I really hope I am not the only one with this issue and that somehow I can fix it / calibrate it without sending it back

Cheers everyone!

[rs-eos]

From your photos, it appears you're still focusing on near objects.

With the focal length set at 300mm, stand in one location (or use a tripod).  Focus on the closest possible object you can (right around the lenses' minimum focus distance).  Take a shot.  Then, focus on the most distant object you can (mountain in the background, daytime moon, etc.).  Take a second shot.  Compare the recorded focal lengths.

The first photo would most likely give you values closer to the 267 mm as you're finding.  But the second photo should give you values much closer to 300 mm.

Having said that, perhaps take a third photo of some object that is in between your close and furthest object and see what focal length you get.

[MikeSowsun]

Your lens clearly needs service. The digital focal length should match the physical markings and is not effected by focus breathing. This has been confirmed by various reviewers and review videos. 

[MickKazik]

Hello Mike, thank you for contributing!

I have something to report, I took few more test shots outside (as Ricky suggested) but it was more so we can move on from the focus breathing idea as I was confident this is not the problem in this case.

As predicted, the issue persists but there is something else to add. When fully extended to "300mm" (on the barell) it just doesn't focus at all. It doesn't even hunt for focus. In fact, I couldn't even take the shot with One Shot focus mode, only managed one (blurry) with Servo. 

Metadata shows 267mm at 300mm. Photos taken with Canon 200D (SL2).

Photos attached.

[jrhoffman75]

Since you say you just received it return to vendor and exchange for new item.