EOS R5 Eclipse photography - Questions on lens care and viewfinder usage

[cambridgevet]

Planned on shooting 8 April eclipse with two R5's...one with the RF15 - 35  at 20mm, the other with the RF100 - 500 at 400mm, at 5 minute intervals. Should the lenses be covered or capped between shots with ND 16.5 filters in place until near totality. Also, is it safe to use the viewfinder during partial stages? An EVF means you are not looking at the sun itself but a digital image, right? I am assuming this protects you completely from UV an IR. The LCD, even with a shade, is pretty hard to use even with the brightness cranked all the way up so using the viewfinder for checking focus and reentering the sun much easier. Thanks for any input here.

[kvbarkley]

Only open the lens at totality or just before. Do so "just before" at your own risk.

I am not sure why you want the 20mm or even the 400 mm.

From here:

https://community.usa.canon.com/t5/EOS-DSLR-Mirrorless-Cameras/Getting-prepared-for-the-eclipse/td-p...

At 20mm the sun will be only 49 pixels wide on your frame.

At 400 mm you will get 795 pixels and at 500 you will get 993 pixels. I suggest going with 500 mm.

[cambridgevet]

20 mm multiple exposures over the ~4hrs...combine all phases in one image with landscape. 400mm so as not to overfill the screen to allow for the full corona at totality. 500 may be too large an image, end up with cropped corona...just being cautious. Any idea on my viewfinder question?

[kvbarkley]

As long as you have a filter, it is safe to use the viewfinder. It is *probably* safe at at some %  without a filter, but I am not going to tell you it is absolutely OK. Note that those bits where that % is in focus get the full blast of the sun.

[cambridgevet]

Thanks for that. Way too much thought going into planning for this event...chances of clear skies in northern VT are about 30% so all may be for naught. But also being forced to learn a lot about my camera so even if the day is a bust it will (almost) be worth it. 

[kvbarkley]

I only get 45%.

I have never had a clear shot of a total eclipse,  it has either been cloudy, annular or partial.