How to use Apo-Rodagon?

[naaldvoerder]

I use a Apo-Rodagon 50mm for enlarging. What would be the optimum aperture to use with this lens?

Jaap Jan

 

[craigclu]

If you are absolutely assured of all-plane alignments of your enlarger, I believe ƒ4 or ƒ5.6 are best with this lens. I use it and a Schneider 90 APO and with the combination of my materials and lighting source has me running long enough exposures 1½ to 2 stops open (15-20 seconds). They both seem to perform best at this point of aperture, even though they are very good throughout their range. A number of years back, I did a non-scientific quick test and at large magnifications, I could tell that both lenses seemed best in that range. It takes very little misalignment to negate this, though so that aspect will grow in its significance as ratios go up, too.

What enlarger/light source are you using? Do you have an alignment ritual and equipment to calibrate it? If you feel that you're relatively aligned by eyeball and general edge to edge sharpness is decent, you may be better off exposing at ƒ8+ and gaining some depth of field forgiveness.

 

[naaldvoerder]

My enlarger is a Dunco 6x7. I'm printing with the Apo at 5.6. I do have a homemade laserallignement tool, but still feel my prints are not sharp enough, compared to prints made with a Rodagon at f8. I checked every plane imaginable, head, newtonglas and lens itself, with enlargerhead at top of the collum. Now i feel the negative carrier might not close tightly enough....

 

[Early Riser]

My understanding is that the APO Rodagons are optimised for one stop down. However if you intend on printing so wide open use a glass carrier and make certain that your enlarger in properly aligned.