EOS Ra: A great Full Frame Astrophotography mirrorless camera...

quiquae wrote:

Very interesting review and breathtaking nightscapes, thank you.

I probably should have held off on posting the review until I'd spent more time investigating that vignette.  (See below)...  But I really do like the camera.  It meets expectations and some of the other members here certainly seem to know what to do with it.

Interesting that the vignetting doesn't appear to be symmetrical--a bigger region is blacked out in lower left than top right. This suggests that the cause isn't anything in the mirrorless mirror box (because that should cause a symmetrical vignette), but something in the front of the lens.

On my EOS 6D, this lens produced a very subtle lopsided soft-vignette.  It was subtle but one corner was just a little darker than the light-falloff in the other corners when shooting with the aperture wide open.

So...I hate to bring up such a silly amateurish point to an expert like you, Marco...but are you sure the lens hood was screwed all the way in?

I think there's a few astro-shooters in here with a lot more experience than me.  The lens hood was indeed in place securely!  But I think you're right... One of the reasons I kept the hood on is because this is a wide lens and I once did a long exposure of the night sky about 6 years ago and ended up with a weird orange illumination from a distant sodium-type street light in my shots when I reviewed them.  I immediately applied the hood and that solved the issue... I am now thinking that I'll need to investigate this vignetting further because it's just this one lens producing the opaque black corner vignettes.  Another reason I left the hood on was to allow the use of a USB powered lens warmer and I didn't want to bake the bare lens.  It's easier to replace the lens hood than this expensive piece of glass.
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I just got home from a second test with the same 24mm lens (and the EF 50mmL) in the mountains tonight and noticed the following:  When my flashlight illuminated some foreground elements on the ground during a long exposure, the green light (reflected off the grass) cast a green hue on the top-right corner vignette in two different shots.  I also forgot to lock down my tripod head after shifting the camera and as the exposure took place, the camera rotated, creating light trails... and some of those stars producing light trails were ghosting into the vignette... which implies that the view of the sensor is being occluded by something physical.  I suspect it's the lens hood.  I never shoot without it so perhaps I've introduced a wild element here by leaving it on for my Ra shots.  I'm thinking that the EOS Ra offers a wider FOV for this adapted lens than the same wide EF lens would normally offer a DSLR with an EF mount.  I've only just noticed this in some of the shots so I'll need to (sigh) take more shots to determine if I need to shoot without the Canon lens hood in place on this lens.  Canon didn't seem concerned at all.  I'm surprised they didn't suggest the lens hood to be the problem.  I'll find out tomorrow night.
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I just tested the EF 50mm f/1.2L USM lens on the Ra and there was only the usual light-falloff in the corners that was of no consequence - considering the properties of this lens.  There was no hard vignetting like I'm getting from the 24mmL lens.  I'm definitely getting more color and detail from this camera than the non-modded DSLRs.  I'm just about to go to bed but will post some samples when I get up again and download the images.
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White Balance
I set my White Balance correctly for this Modified model camera today using the midday sun and a white-card.  I stored it in the Ra camera as the Custom WB setting to be used for Astro... But when I went out to the mountains a few hours ago, I literally forgot to apply the Custom White Balance and left the camera on Auto WB by mistake.  The shots were fine.  Better than the first night.  But I need to use the Custom WB to see what the camera can do.  I now need to do this AGAIN with the Custom WB applied.  It's almost 6am here... I have to get some sleep. Back later...