Depth of Field for Enlarging Lens

[John Layton]

Keep in mind that yes...while there is indeed an amount of focus "slop" at the paper (easel) plane, there is practically none at the negative plane - and this is where the DOF in minuscule and yet if some inaccuracy does exist within this upper plane, stopping down can help a bit, sometimes well enough that doing this is well worth the risk of diffraction, although the other expense of possibly very long exposure times (and a bit of attendant reciprocity failure).

My remedy? Use a really clean glass-plate carrier and spend a bit of time carefully aligning the enlarger. Well worth the effort!

[Tin Can]

I use the Laser check on all my enlargers

stop down 3

and use 3 different focusers

and matte paper

as I have very poor eyesight

still a good hobby

[xkaes]

Now you can laugh at the people that put a piece of paper under the focus loupe. I do, however, so I don't scratch the easel

Since all of my easels are black (to avoid reflective light), I have to have a scrap piece of photo paper in the easel to compose on anyway -- so putting the grain focuser on paper is no problem at all.

[John Layton]

...interesting about that black easel surface. I did this years ago - and utilized a full sheet of fixed/washed out photo paper on which to focus...then removed to do testing and full-sized prints (a bit difficult to see test areas!). Now I've "moved on" to Saunders easels in "focal yellow," which, by virtue of this color, I assume helps to minimize any possible issues due to reflectance.

But truth be told...most of the easels in any number of my student's darkrooms over the years have been white - and I really could not see a difference in those prints vs. prints created on the yellow or black surfaced ones.

A bit counter-intuitive perhaps...but then again, think about all of that white paper (base) which exists underneath the actual emulsion layer(s) of a given paper. One might think that were there to be any "reflectance" issues (perhaps resulting in some ghosting/diffusion), then this might be associated with the paper itself. But does this (ghosting/diffusion) happen? Nooooo.

[Drew Wiley]

I'd be more worried about any baseboard or easel whiteness reflecting back up toward the enlarger, and then back off anything shiny up there, or a bright wall background. I've re-laminated most of my baseboards with black Formica; and easels I have made myself are black. But I have some yellow Saunders easels too; and my Durst L138 enlarger still has a white laminate baseboard. I simply cut off any stray light beyond the image area using the built-in adjustable masking blades right below the negative stage. For really fussy applications, I wrap the stainless enlarger column with a nearby roll of non-reflective black rubber. But that's necessary only when doing copystand work using the enlarger, or perhaps when enlarging onto film, not for general printing.

[ic-racer]

Comparing a step wedge contact printed with the same step wedge projection printed will show the combined effects of lens flare, bellows flare, stray light on the baseboard, etc, etc,. It can be a humbling test.

[Drew Wiley]

Flare is easy to control in an enlarger if one takes the effort. So is stray light bouncing off a baseboard or whatever.

[Tin Can]

I have used a large Dark Cloth to wrap my big enlargers, that spill light

Most do leak light

[Drew Wiley]

The whole underlying question is why someone needs a lot of depth of field in an enlarging lens to begin with. I strive for as shallow a possible depth of field, critically focused on the emulsion grain or dye cloud structure itself, but ideally with any registered sheet of masking film, or the outer surfaces of the carrier glass, somewhat out of focus.

[Andrew O'Neill]

I always made sure the three stages were aligned with this zig-align gizmo I have. I did a f/stop test with my Nikkor 150, and 2 stops down was ideal. Honestly though, I never really gave DOF a thought when printing...