What's the ratio of enlarging 4x5 to 8x10?

[bobwysiwyg]

Just curious about this one. If you take a 4x5 neg. and enlarge it to an 8x10 print, are you enlarging it 4X based on an area ratio or are you enlarging 2X based on linear measurements?

 

[David A. Goldfarb]

Generally in photography linear ratios are used for magnification and enlargement, so 4x5" to 8x10" is usually called a 2x enlargement. It might not always make sense to do it that way, and sometimes it's important to understand that the enlargement by area is different from the linear measurement, but that's how it's done.

 

[Mick Fagan]

The general consensus is a 4x5 neg enlarged to 8x10 is a two times enlargement factor.

In a darkroom, that is the way it is understood.

Mick.

 

[bobwysiwyg]

Thanks, actually, the linear approach always made more sense and is the way I have always thought about it. I recalled once seeing something to the contrary, i.e., referring to the area and it has bugged me since.

 

[MattKing]

Referring to the area does make sense if you are considering the issue of how the exposure needs to change (2 stops), but otherwise, the linear approach is better.

Matt

 

[AgX]

If one speaks of a 2x linear enlargement, how would you designate the respective area-ratio enlargement? Is there any adjective corresponding to `area-ratio´? Would you speak of a 4x `area-related´ enlargement?

 

[Jeremy]

I recalled once seeing something to the contrary, i.e., referring to the area and it has bugged me since.

I find alt process printers refer to the increase in area much more often than linear enlargement scale as you have to measure your coating solutions by area covered, i.e. an 8" x 10" print takes 4x the solution a 4" x 5" print takes. Maybe the person who referred to area also does alt printing.

 

[Mike Crawford]

And what about the inverse square law? First thing we learnt at college!

 

[jgjbowen]

Maybe I can convince Kodak that my 8x10 film should only be twice the price of my 4x5 film :rolleyes: