180mm @ 4x5 is what @ 5x7?

[mowbray]

hi everybody,
i was wondering what a 180mm on a 4x5 format corresponds to on 5x7 format. what is the factor?

cheers,
m

[benrains]

Based on the ratio of the diagonals of the two formats, you'd need something around 1.34 times longer. That would be a 240mm lens.

[Jim Galli]

Probably 240 mm. 1.4 would be a good factor for you. 180 240 360 on 4X5 5X7 8X10 respectively would have very close aspect ratios.

[Andrew O'Neill]

Do you mean, what would be the equivalent lens on 5x7? If that is what you mean, then I believe it would be about 235mm.

[Andrew O'Neill]

Those guys said 240...not bad for a guess, eh?

[mowbray]

235mm-great, thanks guys. i'm looking for a viewfinder and might get a 5x7 even though i'm using a 4x5 camera...that's the background of my question,

cheers,
m

[Archphoto]

Hold it !Please

If you are using a 180 on 4x5 you will need a 240 for 5x7 for the same angle !
A 180 on 4x5 becomes a 128 on 5x7 compared to 4x5.
That is if the IC covers 5x7.

Peter

[mowbray]

erm,just to make sure:
looking through a 5x7 viewfinder @240mm will give me the same FRAMING like the 180mm on the 4x5 camera, right?

[Gem Singer]

Yes. Looking at the image from a 240 lens on the ground glass of a 5X7 camera will be the same perspective as looking at the image from a 180 lens on the ground glass of a 4X5 camera.

[Helcio J Tagliolatto]

250mm