quick printing questionsi

[coops]

I have several packs of Ilford paper, all the same, in sizes 5x7, 8x10 and 16x20 I think. If I do test strips on say the 8x10 and make prints I like, can the time, exposure etc be applied to the other size papers, or does each size need to be tested?
Thanks

[Mick Fagan]

My experience is that you will, or should be, within about 1/8 of a stop, for speed.

For contrast control, my experience is that you should be within 1/4 of a grade.

Basically if I have a good print on either 5x7, 8x10 or 12x16 Ilford MGIV RC paper that I use, these parameters hold true.

Mick.

[jeroldharter]

I think you might be asking two different questions.

If the different sized papers come from the same batch or emulsion number, they should be very similar. So if you printed a 5x7 inch image on any of the 3 sizes of paper, the base expsoure, dodges/burns, etc should be the same.

If the emulsion numbers are different, you might see subtle changes that require re-testing for tight control.

In the other hand, if you make an 8x10 and then try to print the same image 11x14, then of course you will need to do test strips because of the increase in magnification. Apart from the attenuation of light from the enlargement of the image above the original 8x10, the larger prints will result in somewhat more flare which can reduce contrast. So you might need to punch up contrast slightly (1/12 - 1/6 stop more magenta for example when split printing).

[Brian Ellis]

I have several packs of Ilford paper, all the same, in sizes 5x7, 8x10 and 16x20 I think. If I do test strips on say the 8x10 and make prints I like, can the time, exposure etc be applied to the other size papers, or does each size need to be tested?
Thanks

When you switch from one paper size to another you'll have to change the height of the enlarger head (unless, of course, the image size stays the same which seldom would be the case). Changing the height of the head will change your exposure times. In the old days there used to be various methods of calculating the new times without running new tests. I used to use the wheelie system that was contained in the old Kodak B&W Darkrrom Guide. But unless you have something like that you'll need to retest at the new paper size.