Calibrating lens to a Compur shutter

[ron_lawrence1]

I have 90 mm Super Angulon in a defective Compur shutter. I also have a spare Compur shutter in very nice condition with the same min/max aperture. If I were to exchange shutters, what kind of calibration is needed to match the lens to the new shutter? When I take the lens elements off the defective shutter, I see no shims. Thanks for your guidence!

[david_goldfarb]

If the thread matches and the lenses screw into the new shutter, you

could use a depth gauge to make sure the distance from the rear lens

of each cell to the aperture blades is the same for the new shutter.

If not, you could have the shutter modified and adapter rings made

(see www.skgrimes.com).

 

<p>

 

The aperture markings might not apply to the new lens if they were

originally for another lens. You could determine that either by

measuring the actual diameter of the apertures for each shutter at

each setting. If not, you could draw a new aperture scale and stick

it on the lens (either using the formula: f-stop=focal

length/diameter of the aperture, or using a light meter with a booster

capable of taking groundglass readings) or you could have a new scale

engraved.

[david_goldfarb]

For those disturbed by the unresolved "either," the second sentence of

second paragraph above should end: "or with a light meter."

[michael_briggs2]

Most likely, you can just switch the lens barrels to the spare Compur

shutter. As mass produced items, lenses and shutters are intended to

be made precisely enough that they are interchangable. One exception

is that the spacing of the lens elements of wide angle lenses is

critical and is sometimes fine tuned with thin washers. Your lens

lacks such shims, so you don't have to worry about it. Otherwise you

would transfer the shims too.

 

<p>

 

If you want to be really sure, measure the distance from the back of

the back cell to the front of the front cell using machinist's

calipers. This distance should be the same with the lens cells

mounted in either shutter.

 

<p>

 

If the aperture scales are the same, then you are also ok there.

[bob_salomon3]

It is critically impportant with wide angle lenses that they be

re-collimated when remounted in a new shutter. Normally this

should be done by a qualified repair shop with the proper

equipment.

 

<p>

 

Additionally the aperture scales need to be re calibrated