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# Thread: 12x20 Viewing Card

1. ## 12x20 Viewing Card

I was thinking about a viewing card, much like the ones for 4x5, to use with my 12x20 camera. Holding a large card with a 12x20 cutout is a bit too much so I decided to scale it down. I divided each dimension by 4 and came up with an 8x10 card, easy to carry, with a 3x5 cutout. Now my problem is how close or far away do I need to hold it from my eye to approximate the correct composition. I have a 610mm lens and a 450 lens.

Any suggestions?

Thanks

Gary

2. gary, the gut reaction answer would be:
4.5" away from your face for the 450mm lens
6" away from your face for the 600

basically thats going with the focal length being the distance from film plane to the lens center... 450mm/4 = 112.5mm = 4" 600mm/4=150mm = 6"
likely not EXACT but close enough I would think.

3. Originally Posted by Gary892
I was thinking about a viewing card, much like the ones for 4x5, to use with my 12x20 camera. Holding a large card with a 12x20 cutout is a bit too much so I decided to scale it down. I divided each dimension by 4 and came up with an 8x10 card, easy to carry, with a 3x5 cutout. Now my problem is how close or far away do I need to hold it from my eye to approximate the correct composition. I have a 610mm lens and a 450 lens.

Any suggestions?

Thanks

Gary

My viewing card for 12X20 is 6X10 inches, or 1/2 the dimension of the format. Proper viewing distance for this card is 1/2 the focal length of the taking lenses. For example, if you are using a 600mm lens place the card 300mm from your eyes.

One trick you might want to consider is to attach a nylon cord to the viewing card, with a knot in the cord at the proper distance for every focal length you own. To view, place the knot between your teeth and hold the card centered away from your face, and level on both axis.

Sandy King

4. Originally Posted by sanking
One trick you might want to consider is to attach a nylon cord to the viewing card, with a knot in the cord at the proper distance for every focal length you own. To view, place the knot between your teeth and hold the card centered away from your face, and level on both axis.

Sandy King
In which case, you are bound to be asked the question .....

"Is that a Hasselblad?"

(Sorry, I couldn't resist)

Matt

P.S. The cord and card sound like a great idea for other formats too.

5. Make sure you dip the cord in something that tastes good.

6. Originally Posted by Robert Hall
Make sure you dip the cord in something that tastes good.
Or use dental floss!

Steve.

7. Set the camera up and focus look at the ground glass for referenece points. Then look through the viewing card when you find the correct distance from your eye to match what you see on the ground glass. Take a string and attach it to the card and then tie a knot in it at the correct distance.

8. Thanks Richard, very easy way to work. One for the notebook.

9. Lots of great suggestions.

I made a card using Sandy's suggestion about the dimensions.

I am going to make two pieces of cord, one following what Sandy said and one following what Richard said. I'll then decide which method works best for me.

Thanks to everyone for replying.

Gary

10. Gary, use 1/4 the FL and you will be fine.

I made a similar viewing device for 4x5. Basically, it uses the same "window" size in the 4x5 format, but is a simple brass rod bent into a rectangle. There is a length of brass strap (hobby shop stuff, somewhat soft, but it works), a wood block with a brass tube epoxied in place and scored marks on the brass strap. A friction fit is all that is needed. Since the 4x5 aspect ratio is 1:1 in this case, I have marks at 65mm, 90mm, 125mm, 180mm, 240mm and 300mm is full extension.

To use this device for 8x10, I use 1/2 the focal length or just under 125mm for the 240mm G-Claron from "the little green men" lens (thanks Jim), 150mm for the 300mm and 240mm for the 480mm lens. tim

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