f-Stops for Ilex 7.5" Paragon

I have an Ilex Paragon Anastigmat 7.5" f4.5 in a No. 3 X Universal shutter. The lens came with a Meridian 4x5B that I purchased. The f-stops have been marked over (ugh). I'm not sure if this is the original shutter. Is there a way for me to calculate the f-stops?

Bob K.

Divide the f/number you want to mark on the shutter into the 7.5" focal length of your lens. This will give the apparent diameter of the aperture as seen through the front of the lens. Adjust the diaphragm until it appears to be that figure. For example, to mark f/4.5 on the shutter, the apparent diameter of the diaphragm should be 7.5/4.5 or 1 2/3 inches. For maximum accuracy, move your eye by that 1 2/3 inches as you move from checking one edge of the diaphragm to the other, so you are always looking directly into the front of the lens instead of looking at a slight angle.

It does sound like the shutter aperture scale was originally calibrated for a different FL. An easier option would be to photograph the scale of a similar 7½" Paragon, I think I have one somewhere in a cabinet here. I'll see what I can do later today or tomorrow.

Ian

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Originally Posted by IanG

It does sound like the shutter aperture scale was originally calibrated for a different FL. An easier option would be to photograph the scale of a similar 7½" Paragon, I think I have one somewhere in a cabinet here. I'll see what I can do later today or tomorrow.

Ian

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Well, you know that the lens wide open is f4.5, So you can aim the camera at an evenly lit wall (but camera is focused for infinity), and if you have a decent digital spotmeter, you can read exactly the same spot on the GG (under dark cloth) as you stop down, and if there is a tape label where the scale should be, every time you read an f stop lower, dab a mark with a pen... Then mark the f stop # next to that mark...

This works quite well if you do it right to get a close (ballpark) f # yourself for the lens testing... (This is not for shooting, as different GG's have different brightness densities, but good enough to make a scale...

If you love the lens, send it to SK Grimes for a new scale (not too much $$$)...

Good luck!!!

Steve K

Steve, that's just what I did. SK Grimes has a very reasonable price.

Thanks.

Quote:

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Originally Posted by LabRat

Well, you know that the lens wide open is f4.5, So you can aim the camera at an evenly lit wall (but camera is focused for infinity), and if you have a decent digital spotmeter, you can read exactly the same spot on the GG (under dark cloth) as you stop down, and if there is a tape label where the scale should be, every time you read an f stop lower, dab a mark with a pen... Then mark the f stop # next to that mark...

This works quite well if you do it right to get a close (ballpark) f # yourself for the lens testing... (This is not for shooting, as different GG's have different brightness densities, but good enough to make a scale...

If you love the lens, send it to SK Grimes for a new scale (not too much $$$)...

Good luck!!!

Steve K

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Reviewing lesson from the past. Great forum, great way to learn.