DIY soft focus

[mdarnton]

Even at the back of the tunnel I have it mounted in, it does seem to cover. Looking through the corners of my GG I see a lozenge of clear lens of about 1/3 of the full glass, so illumination will be there but less. Performance goes down as you get larger than 5x7, but not as quickly as a simple close-up lens does, and there's an amount of distortion that gets worse, the larger the film size but isn't noticible on 4x5.

I would call it "coverage" but I wouldn't call it "good". :-)

Here's a quick view through my 8x10 camera. Don't take the sharpness as shown here seriously--just the coverage and distortion:


achromat-on-8x10
by Michael Darnton, on Flickr

[Mark Sawyer]

Does the 58mm cover more than 4x5? I'm wondering if I can get one to cover 8x10 which is my primary format.

58mm is the mounting thread size, and you can get a variety of focal lengths in that size. Get a focal length of around 333mm (+3 diopter) and you're set. The single menisci illuminate a very large circle, but if you go with a 250mm (+4) or shorter, your corners will get very crappy very fast, which may or may not be an effect you like.

[mdarnton]

I picked 58mm because it's the size of the shutter I had to put it on. I have checked the Ilex #4 and though the threads are larger diameter, the diaphragm is smaller than the Copal 3, around 40m, so it probably wouldn't be as good of a combination. I just bought a cheap #4 to mess with, but it turns out that the lens in it was in MUCH better condition than the seller described, so it's staying in place. The Ilex #5 diaphragm is 62mm, maximum, but that shutter is a lot rarer. I like Ilex shutters, but I never realized before this how small the hole is for such a large shutter!

The achromatic close-up lenses are available in all the lengths and diameters of regular closeup lenses, but they can be hard to find and expensive. They definitely have a flatter field and more consistent sharpness across the field than a closeup lens. Someone earlier posted a link to a list of many of the available ones, though there are more now, with Ebay available.