Used Canon EF 200mm f/2.8l ii usm .. internal spots

[migEOSRP]

I bought a used Canon 200mm f/2.8l ii usm lens very recently for my EOS RP camera (already that the Canon adapter) from an online retailer with excellent return policy. My question is about internal spots visually evident by looking through the lens. There are no scratches or smudges on the outer exposed lens surfaces and the functionality tested so far seems fine. I'm testing this lens mainly for astrophotography (star field photos etc) and with prelim testing at wide open f/2.8 the stars are reasonably pin-sharp up to the edges. I'm thinking of returning the lens as I think there should be absolutely no internally visible spots of any sort. Any suggestions on helping my decision process?

Also, any suggestions on a Canon RF prime lens in the range 200 to 400mm (but not zoom)? 

[ebiggs1]

"... I need to see evidence that these are really exceptional lenses .. particularly at 200mm zoom..."

IMHO, that would not be a concern all the 70-200mm lense are all very good. I know astro photographer like primes as I used to be one myself. This is totally your call if the IQ is where you want or expect it to be. I would look to see if there is a way you could try one. An R series camera gets the best from RF lenses that are designed for that camera and not from older adapted EF lenses.

[normadel]

Sorry, ebiggs1. You are the one who is wrong. The OP is showing us clear distinct spots, not any of the optical defects you mention. YES, fungus, mold, dust, dirt, coating defects can manifest themselves as what you mention. But NOT clear distinct specks and spots.

[migEOSRP]

Thanks for all the insightful comments by everyone. I'll respond to this after I make a decision based on more testing and/or if I decide to buy a new RP 70-200mm f2.8L or the RP 100-400 f4.5-5.6L

[ebiggs1]

Sorry, norman but that is not what you said let me quote you.

"Dust, dirt, fungus, other particles INSIDE of a lens, or on the SURFACE of a lens, do not show up distinctly in images, if they can be discerned at all."

All I said was, "Fungus and/or mold inside a lens can affect image quality of a lens."

[ebiggs1]

"...if I decide to buy a new RP 70-200mm f2.8L or the RP 100-400 f4.5-5.6L"

Just what is it you are targeting in the night sky? I would certainly not think the 100-4000mm to be a good astro lens for much work.

[migEOSRP]

mid size deep sky objects .. similar to say SVBONY SV555 AstroCamera (f 250mm) but with a bit more zoom in capability.. hence 100 to 400mm.

My astro interests started recently really starting with using a Samsung S23 Ultra phone which gives pleasing (imo) astro shots. Then migrated to better quality spotting scopes .. then added simple tracking. My web articles on this page describes my ongoing journey.

https://www.jensign.com/Astronomy/S23Ultra/indexStars.html

I realize that camera lenses aren't designed for astro shots (I already have the Rokinon 135mm f2 ) but I want a good camera lens that does a good job for double duty .. regular photos/landscape etc and low level astro. And since I really only want to use a small light-weight payload with my AZ-GTi tracker .. and I don't intend to gather a lot of gear .. I have a reasonably clear idea of my wants. 

[migEOSRP]

I have decided to return this refurbished Canon lens based on my visual inspection and an inadequate response from the distributor.

How good is the seal (from dust and moisture/cold condensation internally ) for the L level Canon lenses?  and more specifically for zoom lenses where zoom is external vs totally internal (like the RP 70-200mm f2.8L vs Z model)

[ebiggs1]

"How good is the seal (from dust and moisture/cold condensation internally ) for the L level Canon lenses?"

The back side, the camera side, is always open. There is no dust sealing on any lens. WHen mounted on the camera "L" series is as good as it gets.

[ebiggs1 · Accepted solution]

"I realize that camera lenses aren't designed for astro shots (I already have the Rokinon 135mm f2 ) but I want a good camera lens that does a good job for double duty .. regular photos/landscape etc and low level astro."

Well you see your requirements are almost 180 degrees opposed to what true astrophotographers want and require. They want the best astro capable lens possible hang what else it can do. You want a GP (general purpose) lens and any of the lenses you mentioned will fill the bill. The choice is yours.  You can point any lens towards the sky.

[normadel]

Odd statement. Do you have an L lens?  I have two, 17-40 and 70-300.  They have rubber dust/moisture seals around the mount.