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View Full Version : WTD tips on using a Protar front or rear lens cells alone



Greg
19-Jun-2018, 16:52
Have and use a 12 3/4" f/7.7 BL Protar V11 lens on my 11x14 (front and rear cells being 18 7/8 and 27). Have only once used the 27" cell alone... unfortunately was on a very windy day and the bellows acted like a sail and the exposure had just too much movement to even be contact printed. Have read that when using the front or rear cells alone, using a yellow filter is recommenced. Also there is some focus-shift? Looking for hands on experience with using the front or rear cells of a Protar alone.
thanks...

karl french
19-Jun-2018, 17:03
Place them behind the shutter and stop way down. Some people report focus shift. It's never really been a problem for me. The negatives contact print well, but don't hold up to scanning very well.

EdWorkman
20-Jun-2018, 11:16
I have the 11+24 combo
Putting a single element out front protects the shutter blades. I did check focus shift, probly with the 24" element, and found it to be 3/8 inch
regards

EdWorkman
20-Jun-2018, 11:17
OOPS I mis typed The combo is just shy of 12"", using the 24 and the 18+ as is yours

Keith Fleming
20-Jun-2018, 19:48
Ed Workman raises an important point about danger to the shutter blades if there is no Protar lens cell on the front of the shutter. Since conventional wisdom is that the single Protar cell should be in the rear of the shutter, I had S. K. Grimes make me a filter adapter that allowed me to use a 52 mm filter on the front of the shutter to protect the shutter blades.

Ultimately I had Grimes make a second filter adapter to that I could experiment with a protective filter on the front of the shutter and a 52 mm Nikon close-up lens on the rear as a meniscus lens. Also, I can put Nikon close-up filters on both sides of the shutter and have a variant of a Periskop lens. Different combinations of close-up lenses give different focal lengths too. My summer project is to experiment with different combinations.

Keith

karl french
20-Jun-2018, 20:27
How often do you stick your thumb into the shutter blades? Just be careful.

Vaughn
20-Jun-2018, 22:55
How often do you stick your thumb into the shutter blades? Just be careful.

I was taking multiple exposures of the moon in eclispe...an exposure every 10 minutes. The blades exposed to the cool night air eventually stuck open after about the 6th exposure. (TR lens, 27" element behind).

j.e.simmons
21-Jun-2018, 03:54
Put the filter inside the bellows. Focus with the filter in place.

EdWorkman
21-Jun-2018, 16:01
If one peruses literature from the lens makers [when convertibles were the rage] one finds both views
In front to protect the blades
In back for ? I forget
But in front the blows length may become 'adequate' rather than 'strained'

I made a 4x5 neg with the Protar, can't recall if it was combined or just the 24" but I was trying to get max distance.
In any case , I did capture a background mountain far far away, delicate separated tones in the no-filter haze