EOS R5 & R6 How to Get Full Picture for Digiscoping

[calexander27]

I have an R5 & R6.  Are there certain settings that need to be changed to get a full picture?  When I use my 1DX, I see a full picture, unlike with the R5 & R6 which just shows you a  small round circle.  Any help would be appreciated.  I have the required equipment for digiscoping, so again any help would be appreciated.

[rs-eos]

What lens are you using? Sounds like an EF-S lens?

[calexander27]

I'm using Swarvoski TLS APO 43 mm (apochromat telephoto lens system) designed to fit on a Canon body. I have full a picture with the 1DX but not the R5 & R6.

[deebatman316]

Are you sure you get a full image in the viewfinder of the 1DX. This lens appears that it doesn't interface with the camera at all. All of the cameras mentioned are Full Frame.

[calexander27]

When I bumped up the ISO, it did.  When you lower the ISO it would go back to a circle, but much larger then the R5 & R6

[Waddizzle]

What type of mount adapter are you using?  The 1Dx and R5/R6 bodies would require different mount adapter configuations.

[calexander27]

For the R5 & R6 I have the RF/EF adaptor ring which the Swarovski T2 telescope adapter

[Waddizzle]

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@calexander27 wrote:

For the R5 & R6 I have the RF/EF adaptor ring which the Swarovski T2 telescope adapter

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I don’t know.  That really is peculiar.  I cannot think of a setting in the MILC bodies that would cause vignetting.  Cropping, yes,  Vignetting, no.

Just to confirm.  What you are saying is that if you setup the scope with the 1Dx, then you get a normal image.  If you swap the 1Dx for the R5/R6, then your image has a high degree of vignetting….in other words, a small image circle.

[EDIT] What is your shutter mode?  Have the enabled the setting that allows the camera to fire the shutter without a lens attached?