Edges of Photos out of Focus

[snark]

I am using a Beseler 23C II enlarger with dichroic head and a Rodenstok 90mm lens to expose negatives of landscapes shot with an RB67. I most often print the entire negative, little cropping). The middle 2/3 of the negative is clear as a bell, the sides increasingly out of focus. I have examined the negatives under a magnifier and they are crystal clear, so the problem is with the enlarging and obviously I suspect the lens. Yes, in the field I tend to err on the side of overexposure, so often I have to open the enlarger lens all the way up. Comments, suggestions?

 

[Strodav]

It's been a while since I was in the darkroom, but three things crossed my mind after reading your post. 1) Double check to make sure the negative is being held flat and there isn't some mechanical malfunction in the holder. 2) Is the paper laying flat? 3) Try a smaller aperture and give it more time, A 90mm lens should would just fine for a medium format film.

 

[480sparky]

Can you refocus the lens and get the edges into focus (disregarding whether the center is or not)?

 

[Rickbb]

The enlarger lens has a DOF just like the camera. Opening the enlarger lens all the way is most likely your issue.

I always used to stop it down all the way for the exposure, wide open for focus. Yes, the exposure time will seem to take forever with a dark neg, but you will get edge to edge sharpness that way.

And as Strovdav said, make sure the neg and paper are both flat.

 

[webestang64]

I always used to stop it down all the way for the exposure, wide open for focus.

Agree.....Wide open for focus. You really should not print anything less then F8. A lot of the time I use F11 or F16 as I do a lot of dodge/burn.

 

[NS: Nikon Shooter]

The enlarger lens has a DOF just like the camera.

Indeed, ƒ stops works both ways when it come to DoF

 

[IanG]

What enlarger lens are you using, cheap ones are poor at wider apertures.

Ian

 

[webestang64]

What enlarger lens are you using, cheap ones are poor at wider apertures.

Ian

I am using a Beseler 23C II enlarger with dichroic head and a Rodenstok 90mm lens

I assume the OP forgot the "c", Rodenstock.
I use Rodenstock and they are the best in my mind.

 

[IanG]

The question should be which Rodenstock lens, they vary.

Ian

 

[webestang64]

Then I guess I have the best ones.

 

[Rickbb]

I have the same enlarger and the stock lenses that came with it have been excellent. I’ll have to check which they are but have done 20x24 prints from 2x3 3/4 B&W negs and 11x14 color from 35mm. I was quite pleased with the sharpness edge to edge.