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#1 tim orourke

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Posted 13 April 2008 - 07:27 PM

I have heard a lot about "measuring focus" but never really understood how to do it. I know to focus with a non reflex camera you need to use a tape measure to get the sharpest focus possible, what I'm confused with is at what part of the lens/camera do I start to measure from? (the back, middle or tip of the lens?) I was also wondering about focusing to infinity, I've read a little bit about it but i was wondering what would be the best situation to use infinity for. sorry if this might be a bit hard to understand, I'm a "noob" to this stuff but I would love to learn more. If anyone could break it down for me that would be greatly appreciated, and if this has already been asked many times then I apologize. Thanks again!
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#2 Tim Carroll

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Posted 13 April 2008 - 08:58 PM

I know to focus with a non reflex camera you need to use a tape measure to get the sharpest focus possible, what I'm confused with is at what part of the lens/camera do I start to measure from? (the back, middle or tip of the lens?)


Not sure what camera you are using, but most cameras have a "Film Plane" mark on them. It looks like a little "0" with a straight up and down line through it. It tells you (without having to open up the camera and expose/ruin the film) where exactly the plane of the film is as the film sits at the camera gate. That is where you measure to when you use a tape to measure focus, the distance from the subject to the film plane.

Best,
-Tim
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#3 tim orourke

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Posted 13 April 2008 - 10:20 PM

Thanks a lot Tim! As soon as I read your post I went to check my camera and found the Film Plane mark, this is great to know. I have a bolex h-16 I'm pretty sure it is from M series from 1958, and it has a pan cinor 17.5-75mm zoom lens which has a viewfinder but i've looked through it many times while playing with focus and it doesn't seem to change. It seems like the viewfinder is only meant for framing things up. Thanks again for the info.

I'm still a bit confused about the focusing to infinity thing though. The lens I have goes from 6ft to 100ft(I think) and then after the 100ft mark is the infinity symbol. My only guess is anything past 100 feet is in the infinity range, but I'm not sure. I'll be looking around a bit to find out, but if anyone can clear that last thing up for me that would be great. thanks.
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#4 Erik Vilhelm

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Posted 14 April 2008 - 04:56 AM

Thanks a lot Tim! As soon as I read your post I went to check my camera and found the Film Plane mark, this is great to know. I have a bolex h-16 I'm pretty sure it is from M series from 1958, and it has a pan cinor 17.5-75mm zoom lens which has a viewfinder but i've looked through it many times while playing with focus and it doesn't seem to change. It seems like the viewfinder is only meant for framing things up. Thanks again for the info.

I'm still a bit confused about the focusing to infinity thing though. The lens I have goes from 6ft to 100ft(I think) and then after the 100ft mark is the infinity symbol. My only guess is anything past 100 feet is in the infinity range, but I'm not sure. I'll be looking around a bit to find out, but if anyone can clear that last thing up for me that would be great. thanks.


I also have a Bolex H-16 M, and it has a viewer with parallax corrector on the side of the camera (not on the lens) for framing.
Try the viewfinder on the lens with full zoom on any close object, and play with the focus to see if it changes.
After 100 ft (say 110ft +) I would set it to infinity.
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#5 David Auner aac

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Posted 14 April 2008 - 10:03 AM

Thanks a lot Tim! As soon as I read your post I went to check my camera and found the Film Plane mark, this is great to know. I have a bolex h-16 I'm pretty sure it is from M series from 1958, and it has a pan cinor 17.5-75mm zoom lens which has a viewfinder but i've looked through it many times while playing with focus and it doesn't seem to change. It seems like the viewfinder is only meant for framing things up.


Hi Tim,

the finder on the Pan Cinor is a reflex finder AFAIK (usually called dog leg finder) and focus should definitely change when looking through the finder. Try zooming all the way and try to change the focus. When shooting wide focus isn't as critical and I assume the finder on the Cinor isn't all that great either and the magnification is rather low.

Regards, Dave
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#6 tim orourke

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Posted 14 April 2008 - 02:15 PM

They only time i have looked through it has been in my house which the lighting is rather dim, thats probably why i haven't been able to tell the difference, some time this week i'll take it out side with me. Thanks for all of the replies.
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#7 Leo Anthony Vale

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Posted 14 April 2008 - 02:42 PM

the finder on the Pan Cinor is a reflex finder AFAIK (usually called dog leg finder) and focus should definitely change when looking through the finder. Try zooming all the way and try to change the focus. When shooting wide focus isn't as critical and I assume the finder on the Cinor isn't all that great either and the magnification is rather low.


On those older Pan Cinors the the prism is located between the zoom section and the backing lens,
so you're not seeing the actual image that hits the film.
Some latter ones might have a "range finder" prism in the viewer, earlier ones have just an aerial image.

Whereas the Angies behind the last element of the lens and there's a ground glass spot to focus on.
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#8 David Auner aac

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Posted 14 April 2008 - 02:54 PM

On those older Pan Cinors the the prism is located between the zoom section and the backing lens, so you're not seeing the actual image that hits the film.


I stand corrected! Should have done my research more thoroughly! Thanks, Leo.

Cheers, Dave
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#9 Jim Carlile

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Posted 27 April 2008 - 02:32 AM

I'm still a bit confused about the focusing to infinity thing though. The lens I have goes from 6ft to 100ft(I think) and then after the 100ft mark is the infinity symbol. My only guess is anything past 100 feet is in the infinity range, but I'm not sure. I'll be looking around a bit to find out, but if anyone can clear that last thing up for me that would be great. thanks.


It means that anything after 100 feet all the way to infinity will be in focus at that setting.
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