Darlot projection lens questions
I recently discovered two Darlot projection lenses that go with my Magic Lantern projector. Here are my questions:
1. Is there anyway of using these on a 4x5?
2. If I wanted to have a flange made for a lens board, how do you measure the threads etc.? Or is there a place that might have them?
3. How do you know what the focal length and aperture are? (there is no aperture iris or waterhouse (?)
4. Is this lens anything like (results) of an antique portrait lens?
I'm just learning about these things. I love the look I'm seeing with the tintypes & wet plates, and am wondering if that can be achieved with normal negatives when using a lens like this.
Thanks in advance!
Jim Galli is proberly the one to ask (and he will proberly chime in soon).
take a look at his home page; there are a lot (or a dar Lot ) of images made with projektion lenses...)
Chances are the lantern lenses will work great on a 4x5 though they may be a little long to get the swirly bokeh. You need a short focal length lens to get that effect with a Petzval (which your Darlot lenses may be). The Petzval design has a cemented doublet lens in the front and a pair of air-spaced thinner lenses at the rear. Petzvals intended for a camera were cut for waterhouse stops, but to get the swirl, you want to use them wide open so no biggy.
To find the approximate focal length, hold the lens some distance away from a light wall (start with perhaps 4" and move out) with the front element pointing outdoors through a window. You will see the bright projected image of the outdoor scene on the wall. Move the lens back and forth until the objects at infinity are sharply focused. The distance from the wall to the rear element will then be the rear focus focal length which is how many of the early lenses were designated. You probably need a 4" to 5" focal length to have the swirl on a 4x5. A 6" lens might show the swirl on a 5x7 and probably just cover a 4x5 without showing that effect.
You need a slightly longer focal length to cover a standard plate or film size with the Petzval design. For example, a 13" Petzval lens would be used for 6.5"x8.5" plates while the normal focal length of a modern lens intended for 8x10 would only be 12".
Check out Dan's (luvcameras) webpage on Petzvals for more information.
Any good machinist should be able to measure the threads for you and many will cut a flange a lot more inexpensively than the photographic machinists who are usually recommended. There are several other ways to mount a lens as well ranging from iris lens clampps (also pricey but versatile since you only need one for a multitude of lenses) or using glazier points or washers to hold the lens in place on a board. I've even known people who used glue guns.
Hi Dorothy, besides the lenses, a big part of the "ethereal" look is the blue sensitivity of wet plate, so it's both the lenses, and the emulsions.
Originally Posted by djkloss
Sure, I'll chime in. Thanks Emil
They are petzval type lenses and will make superb portraits. Very sharp center and then lovely out of focus area surround. As to antique look, they are identical to 1860's era portrait lenses.
If your lens boards are large enough perhaps you can figure out a way to make a hole tight enough that the lens is a good press fit. With wood lens boards I've done this successfully. Making flanges is expensive.
Figuring the aperture is easier than you might think. Measure the glass area in MM. Focus on something at good portrait distance. Now measure from about the center of the lens to the ground glass in MM. Divide the width into the length and you have your effective aperture. IE. the glass is 60mm across. Focus you measure 360mm from GG to center of the lens. You are at f6. Your next challenge is how to control an exposure with no shutter at f6 or whatever it is. On my web pages there is a page about Packard shutters, these can be front mounted. In subdued light with slow film you might also try what we laughingly named the 'jim galli shutter' There's a page about that too.
Good luck. Film is cheap. Have some fun with these, you're lucky to have them.
Last edited by jimgalli; 09-29-2008 at 01:20 AM. Click to view previous post history.
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Here is a little vid I made about using Mr Galli's method (sans camera):
Thank you everyone for all your responses. The video was great! I can't wait to experiment! For years we all laughed at my dad for hanging on to all this stuff in the attic etc. Now I'm discovering just what all this stuff is, and it's like opening a big treasure box. (There's also an Aero-Ektar and a Cooke-Telar tele) Knowing that it's functional is even better. I just hope he never gets wind of my intentions and wants it back
so far so good. I got a sharp image at infinity on a white card (outdoors) to be at about 6". the diameter of the glass is 30mm. so I'm assuming an f/5 on a 6" lens?
I just looked at the link to the website. It says more like a 5 1/2" with a 1 7/8" = f/3. sounds reasonable to me.
now for the mounting part. I have a hole saw for my drill press & a spare lens board for my speed graphic.... let the fun begin!
Last edited by djkloss; 09-29-2008 at 03:42 PM. Click to view previous post history.
I tried out the lens, but when I cleaned it I may not have put it back together correctly. (Maybe that's why the depth of field is so shallow?) I'll have to check it against the other one. (There were two with the projector). I don't know what those triangles are, and the only thing in focus is the bottle in the center. This is a negative scan - if you lower the gamma, it looks better. You can actually see the house across the street in the top of the window.
Cool. That's the magic lantern projection lens look. I also have a Darlot magic lantern lens that gives pretty wild effects. Mine happens to be a triplet rather than a Petzval, but the effects are similar. You probably assembled it just fine, although you can always switch the elements around and see what you get.