Enlargement sizes and aspect ratios for the numerically impaired

Ira Rush · Oct 12, 2009

Enlargement sizes and aspect ratios for the numerically impaired

OK, so Im not a math Geek!

I understand aspect ratios, and how to calculate them.

I understand that for instance 35mm film would have an aspect ratio of 1:1.5 (35mm frame is 24mm in height x 36mm in width, which then equates to a ratio of 36/24 = 1.5).

I understand that an 8x10 sheet of paper would have a aspect ratio of 1.25, (obviously 1.5 is larger than 1.25), and if you wanted to fill the entire 8" x 10" paper with an image, some cropping will necessarily occur at one end or the other, or both.

Taking that same 35mm negative and this time using a 16x20 sheet of paper (aspect ratio of again 1.25) cropping would occur here too.

Now, what I dont understand is how the following is calculated.

35mm film has a format ratio of 1:1.5, so a full-frame print on 16"x20" paper can measure no more than 13.33"x20", otherwise the image would be significantly cropped.

And this

If we take a full frame 35mm negative and enlarge it to make an 8x10" print, we enlarge the long dimension of the negative to match the long dimension of the paper and it results in a print measuring 6.6" wide

How are those precise sizes calculated (13.33 and 6.6)?

Is there some formula to calculate these sizes and to know what the actual width and height of the enlarged print would be?

Thanks in advance

Mike1234 · Oct 12, 2009

It's easier to think of 135 size film as 2:3 ratio (whole numbers)... or the short side is .6667x (or 2/3 times) that of the long side... or the long side is 1.5x (or 1 1/2 times) the short side. So... 6.6667x1.5=10... or 10x.6667=6.6667... or 13.3333x1.5= 20... or 20x.6667=13.3333.

MattKing · Oct 12, 2009

It also helps if you convert both measurements into the same units. Either think of 35mm film as being 1" x 1.5" (it's close enough for most purposes) or think of the paper as being:

8x10 = 20cm x 25cm (200mm x 250mm), and
16x20 = 40cm x 50cm (400mm x 500mm).

You calculate the magnification by dividing the length of long edge of the paper by the length of the long edge of the negative. You then determine how long the short dimension of the printed image is by multiplying the length of the short dimension of the negative by the magnification.

Using the "inches" version:

magnification = 10.0" /1.5" = 6.6666

length of short dimension of printed image = 1.0" x 6.6666= 6.666"

Hope this helps.

Matt

stwb · Oct 12, 2009

Algebra is your friend.

Basic formula in this case would be:
x=long side length of print/aspect ratio of negative.
So in the 8x10 example x=10/1.5 or 6.66666. In the other example x=20/1.5 or 13.333333.

David Brown · Oct 12, 2009

Get you one of these:

http://www.amazon.com/Staedtler-Mar...1?ie=UTF8&s=home-garden&qid=1255401457&sr=8-1

Ira Rush · Oct 13, 2009

stwb said:
Algebra is your friend.....

You know my math professors told me the same thing way back in college but... instead of attending class I cut, and hung out at the track

So where does that leave me now well Im still tearing up losing tickets, Im still wasting valuable paper due to poor cropping/composing and I still suck at math!

Anyway, really, thanks one and all for all the information, it was much appreciated!

(Now, anyone got a tip for the 3rd at Belmont? )

tim k · Oct 13, 2009

Or, you could just crank on your enlarger till it looks "about right". Crop a little, so what? No calculator required.

Ektagraphic · Oct 13, 2009

I do it the same as tim k. Whatever looks right for that particular neg and that paper size I go with.

Mike1234 · Oct 13, 2009

What Tim said!!

phenix · Oct 13, 2009

Ira, Im not sure I really understood your question. However, if your problem is the difference in proportion between the 35mm frame and the standard paper sizes, than here are my comments:

This difference, indeed turns out in either wasting paper (if you keep the proportion of the 35mm frame when enlarging), or in cropping (if you fill all the paper with image). Usually the cropping alternative is choused, because it also helps in correcting the composition.

But, if you require a paper that matches (or gets closer) to the proportions of the 35mm frame, than cut the standard paper formats in two. The 8x10 becomes 2x(8x5), the 11x14 becomes 2x(11x7), the 12x16 becomes 2x(12x8), and so one. Now, check the proportions: 8/5=1.6; 11/7=1.57; 12/8=1.5; etc. Almost no paper waste.

I hope I answered your question,
phenix

tim k · Oct 13, 2009

phenix, Good idea. I am going to write that down somewhere.

Ira Rush · Oct 14, 2009

tim k said:
Or, you could just crank on your enlarger till it looks "about right". Crop a little, so what? No calculator required.

............ and

Ektagraphic said:
I do it the same as tim k. Whatever looks right for that particular neg and that paper size I go with.

Exactly, I agree, that's what I've been doing for years.

But somewhere I came across those statements which I included in my original post and was going nuts trying to figure out how those precise numbers were calculated. I figured (no pun intended) that if I actually knew in advance,what the actual dimensions would be, I could save time (and paper) by more careful composition and time and paper in the darkroom.

Once again, thanks to all!

Mike1234 · Oct 14, 2009

Here's what I think about "standard print sizes". They SUCK!! Print what feels right and don't worry about it!!

Ira Rush · Oct 14, 2009

Mike1234 said:
Here's what I think about "standard print sizes". They SUCK!! Print what feels right and don't worry about it!!

Yes, I agree

And now I see that it gets worse with other formats.

Now that I have had a Math Enlightenment, I figure that I am wasting about 20% of negative image area due to cropping when I am working with 6x6 and 8x10 and a little less than 10% when I shoot 645 and enlarge on 8x10.

Yup paper sizes suck!

(Wow... now that I no longer feel numerically impaired, maybe I can attempt to fix the economy... maybe I can screw around with those numbers... yeah right )

tim k · Oct 14, 2009

In the interest of saving the planet, going green and all, you just don't want to be going around wasting your negatives.
You need a 4x5. The math is so simple even I can do it. 4x5=8x10=no waste.

eddym · Oct 14, 2009

Ira Rush said:
Yes, I agree

And now I see that it gets worse with other formats.

Now that I have had a Math Enlightenment, I figure that I am wasting about 20% of negative image area due to cropping when I am working with 6x6 and 8x10 and a little less than 10% when I shoot 645 and enlarge on 8x10.

Yup paper sizes suck!

(Wow... now that I no longer feel numerically impaired, maybe I can attempt to fix the economy... maybe I can screw around with those numbers... yeah right )

Why don't you just print the negative full frame? Then you don't "waste" any negative space.

Sirius Glass · Oct 14, 2009

eddym said:
Why don't you just print the negative full frame? Then you don't "waste" any negative space.

Ektagraphic · Oct 14, 2009

I like to print full frame too. I love my ganz speed ez-el for this!

clayne · Oct 15, 2009

Plenty of people do NOT crop and just don't fill the entire paper. Nothing wrong with that at all and a healthy amount of print border almost always looks good.

Rick A · Oct 15, 2009

I stopped fretting over cropping issues years ago. I print what pleases me, I crop in my viewfinder. BTW- I get plenty of test strips from printing full frame 6x6 by trimming my paper before printing.

Rick

Enlargement sizes and aspect ratios for the numerically impaired

Moderator

Privacy & Transparency

Privacy & Transparency