180mm @ 4x5 is what @ 5x7?

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

cheers,
m

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.

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.

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.

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

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

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

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?

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.

250mm