Grain Focusing - any advice?

[jeroldharter]

I normally print 11x14 or 16x20 and have no problems focusing.

I use a Beseler 45VXL enlarger with the Dichro 45S light source and a Peak grain focuser.

Lately, I have been printing 8x10's from 4x5 TMAX 100 negatives. If I open the lens up to focus, I sear a hole from my retina to the back of my skull. The grain is so fine and the light is so bright that I rarely feel like I nailed the focus. If I stop the lens down a bit to see more comfortably, then the grain seems layered or imprecise and that does not work very well.

What do others do when trying to focus with a bright light source? Just occurred to me that I have an ND filter that will fit over my enlarging lens. does anyone do that?

[Claire Senft]

You could dial in a large amount of all three colors for focussing. This will cause neutral density.

[bdial]

Stop down for using the focuser. The range of "close to sharp" increases, because you get more depth of field, but "sharp" is still sharp.

[David A. Goldfarb]

I stop down a bit for small prints from big negs. If your lens has any focus shift it may be more accurate in any case to focus near the aperture you're using for the exposure.

[Doremus Scudder]

Jerold,

Stopping down will increase the depth of focus and make it harder to focus. Yes, sharp is sharp, but it is easier to find "sharp" with a very shallow depth of focus. I would use the ND filter and/or dial in neutral density with your dichro head.

If you are really a "sharpness freak," you might try printing with the ND, or reduced light intensity in order to keep your lens aperture close to optimum (usually 2-3 stops down from wide open). Stopping down a lot for small prints because of the brightness of the light source can introduce diffraction degradation.

Good luck.

Doremus Scudder

[ic-racer]

I have experienced this when the focuser lands on a light area of the negative. When I move to a dense portion of the negative then I can focus. My negatives tend to be denser, because I put the image on the straight portion of the cuve, so there is usually a reasonable place to focus. If your negatives are 'thin' with fine grain I can see how it can be challenging. Putting the blue filter on might dim it down and might help.

[Nick Zentena]

Don't focus on the grain. With 4x5 I look for lines etc. It's more like focusing a camera then getting the grain right.

[Jon Shiu]

Would it work to wear sunglasses?

Jon

[Mick Fagan]

I too use TMax 100 in 4x5" and enlarge onto 8x10" paper, I also enlarge onto Ilford Postcard stock, which is a metric sized stock of 150mm wide by 100mm deep or close to 6x4".

I also use a Peak focuser and had exactly the same problem, my course of action was to use the blue filter which came with the Peak focusing unit. Not only does it reduce light by about 2 stops, maybe a bit more, it aids focusing somewhat for me with my enlarger, which is a DeVere 504 with a dichroic head and single 250W globe.

So I think your idea of the ND filter would be quite good. For what it is worth, I also focus on lines or contrast separations between dark and light areas on the negative. At that magnification the grain is just barely focusable, so to speak, with this film.

I had the same problem when enlarging Ektar 25 professional colour negative material a couple of decades ago, unbelievably fine grained film.

Mick.

[Claire Senft]

When using a strongly colored filter for aerial image focus, one must be very careful. The properties of human sight are such that the strong blue color is likely to cause other than the best possible focus. I realize that this filters were sold with high quality magnifiers. I also believe that they were included as standard equipment with the sale of Apo El Nikkor enlarging lenses which I believe most people would consider to be a very high quality optic.

APUG member Mr. Patrick Gainer has done research and been published on this matter.