EOS Rebel T3i When I look through the view finder I noticed dark blue coloring in the corners

[lcparker]

When I look through the view finder I noticed dark blue coloring in the corners.  Do you know the cause and fix?  The camera is a EOS Rebel 3ti.

 

[lcparker]

Canon zoom lens ef 100-400mm 1:4.5-5.6 L IS

[Tronhard]

OK, so if there is no mention of a MkII in the text your referred to, this looks like the MkI version in which case the correct hood is the Canon ET-83C Lens Hood.

[deebatman316]

The OP said that they were NOT using a lens hood. There are other issues going on then.

-Demetrius

EF 16-35mm F/2.8L III USM, EF 24-70mm F/2.8L II USM, EF 28-135mm F/3.5-5.6 IS USM, EF 50 F/1.8 STM

EOS 40D & 5D Mark IV

430EX III-RT & 600EX II-RT

[Tronhard]

Oops, I can't see that post about no lens hood (frustrating, as we have discussed before!).   

That IS puzzling, given that an APS-C sensor camera is not using the whole of the projected image to begin with.  I found this check of vignetting when using such a sensor and it shows no issues:
Canon EF 100-400 mm f/4.5-5.6 L IS USM review - Vignetting - LensTip.com

I cannot find any references to this occurring after doing a web search.  I think it might be prudent to see if the vignetting occurs with a different body - just to rule that out, even if it's not likely.

@LCPARKER:  Can you advise what focal lengths this occurs in, and also what apertures you are using at the time please?

[deebatman316]

Could misaligned lens elements cause a problem with vignetting. For instance if the lens were dropped or something traumatic to the lens happened. But it also sounds strange how a FF lens would cause vignetting like. That shouldn't happen at all.

-Demetrius

EF 16-35mm F/2.8L III USM, EF 24-70mm F/2.8L II USM, EF 28-135mm F/3.5-5.6 IS USM, EF 50 F/1.8 STM

EOS 40D & 5D Mark IV

430EX III-RT & 600EX II-RT

[Tronhard]

Hi Demetrius:
I absolutely concur.  I have owned both versions of the 100-400 and still have the MkII version, with no vignetting happening.  It does seem like an optical issue.   I would recommend referring to Canon Tech support 1-800-OK-CANON and have a chat to them.  I am not sure if the MkI is still supported at this stage, it's an old lens, but it's worth a try.

[deebatman316]

Does this lens say USM on it. I cannot find a non-USM model for that lens in Canon's lens library/ catalog.

-Demetrius

EF 16-35mm F/2.8L III USM, EF 24-70mm F/2.8L II USM, EF 28-135mm F/3.5-5.6 IS USM, EF 50 F/1.8 STM

EOS 40D & 5D Mark IV

430EX III-RT & 600EX II-RT

[Tronhard]

They are both USM lenses Demetrius. 

The MkI version: https://www.dpreview.com/products/canon/lenses/canon_100-400_4p5-5p6_is 
The MkII version: https://www.dpreview.com/products/canon/lenses/canon_100-400_4p5-5p6_ii 

[deebatman316]

I got it now. Some MK I versions of lenses have both a USM and a non-USM variant. I'll look into dpreview for lenses in addition to Canon.

-Demetrius

EF 16-35mm F/2.8L III USM, EF 24-70mm F/2.8L II USM, EF 28-135mm F/3.5-5.6 IS USM, EF 50 F/1.8 STM

EOS 40D & 5D Mark IV

430EX III-RT & 600EX II-RT

[Tronhard]

As Demetrius said, there are two versions of the EF 100-400 L lens.  The MkI is easily recognized because it has a push-pull mechanism to focus, while the MkII requires one to rotate it.  So which one are you using and if you look at the Lens hood, what does it say on the hood - there should be a model number printed on the outside of it.