Studio NSFW wrote:
Three or 4 stops down from wide open is your sharpest aperture.

Beyond that, there are sooo many variables to your question, I’m not sure what you are asking. Do you mean “Taking pictures of the Sun”? Or Taking outdoor pictures illuminated by the Sun”? Or some combination of the two- like a recent set I did in the sunset in Sedona.

If the former, you might try an astrophotography forum rather than one centered around people photography. 

If the latter, well, I was around f16, and popped a strobe to keep the subject from being a silhouette, iso 100, a single  500 w/s strobe at full power with a small scoop reflector, and shutter speed was whatever it was to balance the sky with the subject…I think around 1/15….the sun itself was either behind the subject (makes a great hair light) or below the horizon.

I would but I don't photograph astro stuff too often. So f8 is sharper than f10? I thought less light getting in gives better field of focus? Or is that different than sharpness if the field of focus is plenty deep at a great distance?

Keith R Smith wrote:
I'll try to help as I have done astrophotography. I presume you're using some sort of  powerful neutral density filter so that you're photographing the surface of the sun in order to get sunspots - or you want to photograph the shape of the sun pre and post eclipse..  Focus would be set to basically infinity and depth of field should not matter too much as your subject is so far away.

I'd recommend experimenting - and being very careful. The sun is not to be trifled with. personally I'd start with something about mid range such as f8 or f12 - somewhere around there, but you don't want your shutter speed to go slower than a thirtieth of a second. Also - unless you're tracking, remember that the sun is moving (ok - the earth is rotating but it's all relative), and you want you images as sharp as possible, so you're wanting a fast shutter speed, but not too fast as to flatten the depth of field. So - yeah - experiment - and oh yes, the higher the ISO, the faster speeds you can use but the more 'noisy' the image can get. That's why night sky astro photographers take lots of images of the same target, then 'stack' those images to try and eliminate that noise as well as other aberrations

I hope that helps.
.

I actually got solar filters from thousand oak. I do see sun spots normally, but wasn't sure I could see them better or if I already reached the limit of my telephoto lens.