Different lens delivers different contrast??

I've made a comparison between two print, one from 50mm and one from 80mm. That's the only different, all other factors are the same: Same lens Componon S, same aperture (f8), same negative (135), same enlargement ratio (8x10 print), paper from same box, same chemicals, same filter (grade 1.5), same enlarger (condenser head). Print from the 50mm is quite more contrast than from the 80mm. Anyone please explain me???

Closer look by nake eyes, I also notice that the 50mm print seems to be a little sharper than from the 80mm. Not sure if it's just result of the higher contrast. Both are currently hanging on to dry. I will check the sharpness again with a 4x lupe when they are dry.

Different lenses on cameras give different results, why not on the enlarger? I think every single lens has it's own signature.

Check (with a flashlight) for fog. I've had a Nikkor enlarging lens with internal droplets, probably from the diaphragm lubricant.

would you believe ,this even happens with two lenses of the same type and brand?it's all part of the mystery of photography so nobody will ever know it all.

If you compare the projections of two lenses of different FL but same design and make, at same aperture and magnification, then the lens with longer FL will yield lesser image quality.

AgX said:

If you compare the projections of two lenses of different FL but same design and make, at same aperture and magnification, then the lens with longer FL will yield lesser image quality.

Click to expand...

How do you define lesser image quality?

AgX said:

If you compare the projections of two lenses of different FL but same design and make, at same aperture and magnification, then the lens with longer FL will yield lesser image quality.

Click to expand...

That seems odd to me. AA always seemed to recommend an enlarging lens slightly longer than what would normally be called for. Example, 60-65mm in place of a 50mm and so on. I've used 80mm for 35mm negs with very good results and 105mm for 6X6 equally as good. I guess that goofy guy didn't know beans about enlarging or projection. JW

If that is true, I wouldn't call it "own signature" or "mystery", I'd call it QC issue.
I thought the longer lens just need longer exposure. How can it degrade the image quality?
Just check two lenses. The 80mm has a lot of cleaning marks on the front element, while the 50mm is almost clear. Is this the main reason? I didn't think cleaning marks can decrease contrast that much.

Just change the filter to grade 3.5. It couldn't help...

A number of possibilities.

Two images from lenses of different focal length enlarged to the same magnification will require the same exposure, so that's not the issue.

Haze in the lens or scratches like you describe, if they're significant, can make a difference.

To make the same print with an 80mm and 50mm lens, the head has to be higher with the 80mm, so if there is any vibration in your darkroom, it will show up more with the head higher on the column.

I'd also think that you could be getting more contrast-reducing flare from adjacent walls or other objects (including your shirt) with more space between the lens and the paper. Though it's not necessary to paint the walls of a darkroom black, it's a good idea to black out the areas around the enlarger, just like the inside of a camera is painted black to reduce internal reflections.

AgX said:

If you compare the projections of two lenses of different FL but same design and make, at same aperture and magnification, then the lens with longer FL will yield lesser image quality.

Click to expand...

That is the typical result of MTF tests. However the lens-affected quality falls much less then the film-dependent resolution rises with bigger formats. That is why larger formats are "better".

The same time DOF rises, thus reducing some focal misalignment during enlarging.
And further the question remains what effect will be actually visible in practice. Basically though the MTF's get worse with larger FL-versions of the same lens-design.