Kodak Supermatic aperture scale question.

[Robbie Bedell]

OK. I have a nice Kodak 105mm 3.7 Ektar. I use this on my 2x3 Century Graphic. For reasons I won't bore you with, the Supermatic shutter the lens is in now is from a Kodak 127mm 4.7 Ektar. I no longer have the old shutter. (If I did I would just swap out the face plates) SO...how can I come up with the correct aperture scale for the 105 in it's present shutter? Is there a calculated way to do this or should I just shoot some film and by trial and error learn the settings? It seems the f/8 on the present scale is about a half stop or more underexposed when comparing developed film to a similar lens I have. Thank you! Robbie

www.robbiebedell.photoshelter.com

[LabRat]

You can send the lens to SK Grimes for a new scale for surprisingly little $$$ to do it right, but there is a quick/cheerful way to do it at home...

So you know the lens is f3.7 so that's a start... If you set up camera on tripod outside on bright day, aim it at something evenly lit like a white garage door and have a dark cloth and spotmeter handy... Put a paper tape label over area where aperture plate would reside, then open wide and gradually stop down until iris is beginning to be visible at the edges inside lens... Take sharpie and make dot at that point where the pointer is at... That is f 3.7... Then take spotmeter under dark cloth and place front against GG and place spot right next to center GG marking and remember the meter will always be placed in that exact spot for entire test... Note reading you get... Continue looking at meter reading as you nudge down aperture lever until the reading is (about)about half stop under the first reading, then put another dot on the blank scale... That's f4... Continue stopping down until meter reading drops another stop (that's f5.6) dot and continue slowly stopping down until you find the next stop lower, dot, and so on through the entire scale... Then remove lens, and carefully write in the # for each of those dots, then put a piece of Scotch tape over the #'s so they don't smear...

If you are careful, those #'s will be very close to proper settings... You can also do it by measuring opening with calipers and a little math, but this can also be approximate reading due to visual errors while taking measurment readings, so either way...

I have done this with old unmarked lenses, and it exposed chromes just right...

Good luck!!!

Steve K

[Robbie Bedell]

Steve, You are a genius. I was hoping I would receive an answer that did not require a lot of math. You have come to the rescue. If this has worked well for you with chromes I will be on easy street since I will only be shooting B&W with this camera. Thank you very much Steve! I now know what I will be doing tomorrow!

Robbie

www.robbiebedell.photoshelter.com

[Bob Salomon]

You can send the lens to SK Grimes for a new scale for surprisingly little $$$ to do it right, but there is a quick/cheerful way to do it at home...

So you know the lens is f3.7 so that's a start... If you set up camera on tripod outside on bright day, aim it at something evenly lit like a white garage door and have a dark cloth and spotmeter handy... Put a paper tape label over area where aperture plate would reside, then open wide and gradually stop down until iris is beginning to be visible at the edges inside lens... Take sharpie and make dot at that point where the pointer is at... That is f 3.7... Then take spotmeter under dark cloth and place front against GG and place spot right next to center GG marking and remember the meter will always be placed in that exact spot for entire test... Note reading you get... Continue looking at meter reading as you nudge down aperture lever until the reading is (about)about half stop under the first reading, then put another dot on the blank scale... That's f4... Continue stopping down until meter reading drops another stop (that's f5.6) dot and continue slowly stopping down until you find the next stop lower, dot, and so on through the entire scale... Then remove lens, and carefully write in the # for each of those dots, then put a piece of Scotch tape over the #'s so they don't smear...

If you are careful, those #'s will be very close to proper settings... You can also do it by measuring opening with calipers and a little math, but this can also be approximate reading due to visual errors while taking measurment readings, so either way...

I have done this with old unmarked lenses, and it exposed chromes just right...

Good luck!!!

Steve K

But since this doesn’t take into the absorption loss of the gg and, if used, the fresnel the scale would be off if the gg or the fresnel are ever changed.
The proper way to do this is to use a reading of the evenly illuminated area, preferably an 18% gray card, then a reading through the camera. Note the difference and use that as an exposure factor. Then proceed as you indicated. Then your exposures won’t be effected by that loss from absorption.

[Robbie Bedell]

But since this doesn’t take into the absorption loss of the gg and, if used, the fresnel the scale would be off if the gg or the fresnel are ever changed.
The proper way to do this is to use a reading of the evenly illuminated area, preferably an 18% gray card, then a reading through the camera. Note the difference and use that as an exposure factor. Then proceed as you indicated. Then your exposures won’t be effected by that loss from absorption.

Very in interesting. Thank you Bob. That would make perfect sense, especially with the Century back which is a ground glass and a Fresnel in it's assembly. The combination would make a considerable exposure factor.

[Dan Fromm]

Hmm. I have a 105/3.7 Ektar in Flash Supermatic in front of me. I have a dial caliper in my right hand. The diaphragm is wide open and the pointer is at the 3.7 tick mark. The diaphragm lever is pushed as far towards wide open as it will go. The diaphragm's leaves can't be seen.

The tip of the 4 mark is 4.75 mm from the tip of the 3.7 mark. The tip of the 5.6 mark is 11.8 mm from the tip of the 4 mark. 8, 8.85. 11, 5.75. 16, 3.30. 22, 2.075. 32, 1.65. All measurements taken from center of tick mark to center of tick mark.

[Robbie Bedell]

Hmm. I have a 105/3.7 Ektar in Flash Supermatic in front of me. I have a dial caliper in my right hand. The diaphragm is wide open and the pointer is at the 3.7 tick mark. The diaphragm lever is pushed as far towards wide open as it will go. The diaphragm's leaves can't be seen.

The tip of the 4 mark is 4.75 mm from the tip of the 3.7 mark. The tip of the 5.6 mark is 11.8 mm from the tip of the 4 mark. 8, 8.85. 11, 5.75. 16, 3.30. 22, 2.075. 32, 1.65. All measurements taken from center of tick mark to center of tick mark.

Mr. Fromm, You have just saved me a tremendous amount of time. Thank you very much! I have been looking at photos of 105 mm face plates wondering how to measure. You saved the day. Thank you!!

[Havoc]

But since this doesn’t take into the absorption loss of the gg and, if used, the fresnel the scale would be off if the gg or the fresnel are ever changed.
The proper way to do this is to use a reading of the evenly illuminated area, preferably an 18% gray card, then a reading through the camera. Note the difference and use that as an exposure factor. Then proceed as you indicated. Then your exposures won’t be effected by that loss from absorption.

I don't think that this matters in this case. You set the start of f/3.7 "mechanically". The rest you do by halving light measured at the same spot. You're measuring ratio's, not absolutes.