Printable View
Howdy,
I take it that size matters :>). From what I dug up 135mm is good to print 4x5, does that mean that I should be looking for
XXXmm to do 5x7 ? I'm coming up with 150/180/210 and not sure which one to choose ? Also, what are the characteristics of Companon-S, vs
Nikkor EL, Rodenstock ? I'm presuming that all of these are good.
Anyhoo, any helpful hints would be appreciated.
Les
In order, MM.
Good. Better. Best.
ymmv
Why couldn't one use a 135mm for 5x7 enlarging?
It won't cover the image area adequately. Vignetting will show up in the prints.I use a 180 mm.Quote:
Originally Posted by Pawlowski6132
I use a Componon S 180mm. Works fine.
Which magnification ratio? Image circle gets bigger as magnification gets smaller. The equivalent of taking lens "infinity coverage" is enlarging lens "wall projection coverage." A grain focuser that can image the corners of your projection can answer your question better than a fortune teller, palm reader, or someone that does not have your exact equipment.
For prints 4x or smaller, a good 180mm should do fine. For prints between 4x and 8x, a 210mm is a better choice. For prints greater than 8x, you might want to go slightly longer than normal (maybe a 240mm) though a 210 should do fine even for mural-size prints. BTW, a 210 or 240 will make printing small easier than with a 180. And of course, there are the specialty lenses.
The starting point is the hypotenuse of the film -- for 5x7, that is 210mm. But this varies based on the lens design and the size of the prints you want to make. As the print size increases, the lens moves closer to the film and more coverage is needed. The smaller the largest print size you intend to make, the shorter the focal length you need can be. The best place to start is the specs from the manufacturer -- plus, the longer the focal length, the larger the proportion of the image that is projected by the center of the lens -- the sharpest part!
Simplifying things a little, enlarging lenses are made up from multiple glass lenses stacked together called lens elements. It takes 3 or 4 lens elements to make a half decent enlarging lens, but the corners will be dark and blurred and it will have be used closed down three or four stops to be acceptably sharp. A lens with six elements is usually far superior, only slight corner darkening when wide open, sharp all over, better contrast, best quality is closed down two stops. The category of more than six elements usually brings the word "apo chromatic" into use, which means the chromatic aberration is corrected at three wavelengths rather than the two wavelengths of a regular achromatic lens. These sometimes give best quality closed down only one stop. These are often (much) more expensive and for much work unnecessary.
When shopping for lenses look for six element if you can, these are high quality workhorses of many darkrooms amateur and professional.