Simple modern B&W 8x10 enlarger head

[Tin Can]

Yes it works, or I could be lying... Not!

The 4 images below show my first 3 prints. The 4th print was underexposed from erratic timer.

#1 is an overview of the three 16x20 Ilford MGIV RC prints done on this setup.

#2 Is a 15 second enlargement at f8 from a very dense 8x10 Ilford Delta 100 neg. No filter, straight print.

#3 Is a 4 second exposure also at F8, I estimate 90% black.

#4 Has a layer of 3mm Makrolon LD diffusion added between light source and negative also F8, 4 seconds and is light grey.

I see some corner falloff in both empty prints, I didn't notice it in the RL print.

I used a old Kodak 250 mm Ektanon enlarging lens which most likely caused the slight falloff. I will retest with a 300 mm Rodagon with the same settings and try F16 as well.

[ic-racer]

Looks pretty good so far, but what is the reason for testing wide open? I'd stop down and minimize the lens hotspot and then see what it looks like.

[John Kasaian]

Thanks! This is intriguing.

[Tin Can]

I'm testing 2 stops from wide open at F8 as I believe that is the optimal sharpness of enlarging lenses.

I am going to try F16 shortly with a Rodagon 300mm.

stay tuned.

Looks pretty good so far, but what is the reason for testing wide open? I'd stop down and minimize the lens hotspot and then see what it looks like.

[ic-racer]

I'm testing 2 stops from wide open at F8 as I believe that is the optimal sharpness of enlarging lenses.

I am going to try F16 shortly with a Rodagon 300mm.

stay tuned.

Of course you can monitor your corner sharpness so you know how much to stop that lens down (without relying on any 'believe' ), but un-even illumination is harder to detect when you don't know about the light source. I'd not go more open than f22 or f32 when testing a light source, or when printing for that matter.

[Tin Can]

Yes, I read on your Durst thread you use f22 or f32 with Rodagon 300mm.

How come many sources, such as Darkroom Cookbook advise 2 stops from wide open? Way Beyond Monochrome also says on page 441 optimal is between f5.6 and f11, that's f8!

I am no genius and try to follow good advice to save time.

I also want to start from worst case to better. I used to stop down my 4x5 to f22, but I have been studying more....

Of course you can monitor your corner sharpness so you know how much to stop that lens down (without relying on any 'believe' ), but un-even illumination is harder to detect when you don't know about the light source. I'd not go more open than f22 or f32 when testing a light source, or when printing for that matter.

[analoguey]

This is a very useful thread, Randy. Thanks for starting it.

[ic-racer]

Yes, I read on your Durst thread you use f22 or f32 with Rodagon 300mm.

How come many sources, such as Darkroom Cookbook advise 2 stops from wide open? Way Beyond Monochrome also says on page 441 optimal is between f5.6 and f11, that's f8!

I am no genius and try to follow good advice to save time.

I also want to start from worst case to better. I used to stop down my 4x5 to f22, but I have been studying more....

We don't know the light falloff or MTF curve of your lens to know optimum aperture.
Extrapolating from known curves of other big enlarger lenses we can guess that light falloff gets better right up to minimum aperture.
We can also guess (based on known Componon-S 240mm findings) corner sharpness is poor under the grain magnifier wide open but gets tolerable around f22 to 32 with a 16x20 print. But we don't need to guess, you can check this yourself (you do have a Peak 1 grain magnifier, yes?)

Noting wrong with testing the lens at wider aperture but my hunch is your light source performs better than you show because the light falloff from the lens is hampering the results. If you are only interested in combined light source and lens performance that is fine too. In that case you can either make a center filter or just realize all prints will need a little edge burn (which is frequently the case anyway).

The Durst CLS 2000/1840 8x10 light boxes were perhaps the most well designed 8x10 diffusion sources ever made. Even with that in place, the physics of the lens produces a light falloff requiring an edge burn on most all prints.

I don't have the 240mm or 300mm light falloff curves (anyone??) but the 150 and smaller lenses all follow a similar pattern as shown:

[Tin Can]

No filters were used on any lens or print. all lenses are excellent, clean, scratch free, no fungus, little dust.

Here are the Rodagon 300 mm results. Enlarged about the same on 16x20 Ilford MGIV RC. The 8x10 negative was shot with Rodenstock Sironar-N MC 360 mm f6.8 at f22 in perfect condition on heavy Linhof tripod, no vibration, Linhof Color Kardan 8X10.

#1 Overall shot, the 2 prints of my tools are flat, the grey print I dried face up and it is warped in the middle and reflecting light differently than the dried face down prints. Mistake.

#2 Middle grey exposed for 10 seconds f16 300 mm Rodagon. Falloff compared to the 250 mm Kodak lens is far less. Rodagon wins.

#3 Same old neg as yesterday, exposed for 60 seconds f16 Rodagon 300 mm. Definitely sharper off center than 250 mm Kodak Ektanon and less fall off. Rodagon wins.

#4 Same print from yesterday, exposed for 15 seconds f8 Ektanon. Same sharpness in center shown by reading the center book titles as Rodagon 300 mm, but obviously less sharp at edges reading text in the image extremes. Ektanon will be used for 5X7 negatives.

I realize all enlargements will have falloff from any lens, light source combination. It is the nature of the beast, the edges of a print are lit with 'rays' traveling farther. Basic.

I think the head has proved to me it will be useful for me. ymmv

I am happy and not chasing a magic bullet 8x10 head anymore. I can afford this.

Again a caveat, I only used the the Artogragh 930 light panel, I am no longer experimenting with any other panel. Do your own testing and please post results.

[ic-racer]

Thanks for posting your results.