Diffusion vs. Condenser vs. Format vs. Paper

[Doremus Scudder]

... I just put my condenser comparison prints into the fix. Looking at them and the ones I made with my diffusion enlarger I am certainly not struck with any difference in sharpness/grain either, but do notice the slight bump in contrast...

Ding, ding, ding! We have an answer!!! Congratulations Corran for nailing down the difference between condenser and diffuser.

Seriously, a contrast change along with a bit more trouble with defects (e.g., scratches on the base side) are the only differences between collimated and diffuse light sources. Any increase in "sharpness" is an illusion caused by a contrast increase. The same goes for increased graininess; it's a function of local contrast. The idea that diffuse light somehow affects how the enlarger lens focuses is nonsense (real-world subjects in diffuse light that we photograph aren't inherently less sharp, are they?).

And, although a print made with a diffuse source may be "closer to a contact print," there is a marked difference here too. My enlarged prints made with diffuse sources (color heads) are a bit less contrasty than my contact prints.

So, if you run out of contrast with your diffusion head and need a bit more, you know how to get it.

Best,

Doremus

[Pere Casals]

I also fully agree with the Vestal pointed test. But IMHO the thing still has fine details to review.

Post exposure has an interesting section about that http://ctein.com/PostExposure2ndIllustrated.pdf

See graph 6-16 in page 69, after adjusting contrast etc we see an slightly different character.

Anyway bad difussion designs perhaps are more prone to deliver stray light, that has to be compensated, as kodak technical datasheets state.

Then we have the Durst view on the matter, saying that condenser is fairly superior, that's also a very interesting point of view !!!!

http://www.durst-pro-usa.com/world_images/expro.htm

http://www.durst-pro-usa.com/world_images/theofcon.htm

The Durst notice agressively promotes condensers, while AA liked diffusers... well, it's an interesting debate.

That graph 6-16 in page 69 of Postexposure points to a different shoulder that works on film toe (print shadows are in the paper shoulder...)

IHMO the diffusion enlarger ends in some tonal compression in the scene shadows.

At the end we may need a compression in the shadows (and highligts) because a paper only delivers some 2.0D range and we need a lot of mids, so we can compress shadows more or less in the film toe, in the print shoulder, in the film/paper selection/grade/processing ...or in the enlarger head type.

...so my personal view is that the condenser has a certain footprint in the shadows, but while we have other control variables in that anyway a codenser can help to get an slight SCIM look, IMHO.

In my case I can only compare with my MF enlargers, a condenser Kaiser vs an LPL VC, and I made informal tests. But what I concluded is that I still I have a lot to learn as a printer before exloiting that difference...

[John Layton]

I think you can also achieve very fine adjustments of contrast with a diffuser head on a Beseler 45 enlarger...by using the accessory bellows (above the negative stage) to vary the distance of the diffuser surface to the negative plane. The greater this distance...the (very slightly) greater the contrast. Full disclosure...I have not actually tried this...but a student of mine did years ago - and showed me some results which indicated that it worked! In principle it should - as any light source gets closer to a point with an increase in distance.

[Pere Casals]

I think it makes sense because if diffuser is far then there is way less light bouncing in the bellows, so less stray light because less oblique rays to the bellows... perhaps this may explain it

[neil poulsen]

I first experimented with diffusion enlarging using an Aristo HI intensity head on an Omega D2. Nice head, but inconsistent. I tried using methods suggested by Ansel Adams to obtain consistent results, but to no avail.

This encouraged me to purchase a Zone VI Type I enlarger. To my great frustration, this enlarger was inconsistent in a different way. The overall intensity was consistent, but due to its design, the contrast could significantly vary. Sheesh!

I use a 45s Beseler color head on my current enlarger. It works great, and to my eye, has the same effect as diffusion enlarging. Incandescent bulbs are much more consistent than cold light tubes. In addition, I (easily) integrated a Zone VI sensor and use this head with a Zone VI compensating timer. (Nice, but probably not necessary.) For "neutral" contrast, use no color. For higher contrast, one can use varying degrees of magenta. For lower contrast, use varying degrees of yellow. I rarely need lower contrast. The highest contrast I've used is with a magenta setting of about 35.

As a caution, be careful purchasing a Beseler color head. Their electronic circuitry can go "stale," with the effect that the time it takes for the light bulb to light after the timer turns on can vary by as much as several seconds. (Strange, but true.) Even if this occurs, like it did with mine, there's a fix that involves connecting the light bulb's AC source directly to AC wall current that includes a correctly placed and sized rectifier. It's important that the unit's fan can still operate.

I originally used a condenser head on both 4x5 and smaller formats and, as suggested by Ctein, I saw a subtle aesthetic difference between that and diffusion enlarging that I don't care for. (Vestal, et. al. not withstanding.) I still have that D2 condenser head and can use it with my current enlarger. But, I've never felt the need.

[Oren Grad]

Just wanted to add that I went back and read the section of Ctein's Post Exposure that describes his investigation of this topic. I'd strongly recommend it to anyone seriously interested in this - his discussion of the scientific and methodologic issues raised is as enlightening as his results. Just follow Pere's link above - Ctein has generously continued to make the full text of the book freely available from his website.

[Corran]

This has all been very interesting - specifically, I really didn't know that the condenser would actually increase the contrast on graded papers. This is a great bit of information! Perhaps someone mentioned it to me before on my last thread re: printing, but anyway I have some graded paper here that really needs a bit more contrast for most of my negs so this is super helpful. I was just given 500 sheets of very old Kodabromide G2 paper that still looks great but seems to be printing closer to G0/1 so this is just what it needs.

Here's a quick cell phone snap of the prints I was working on last night. Top is condenser, bottom is diffusion. Doesn't really show things well but the condenser has a nicer contrast. Maybe I'll scan the prints when I have time. These were actually made on some Portriga I was given. Just testing papers this week.



Most importantly it's good to know that sharpness/grain is not affected (any perceived difference being the bump in contrast). The condenser certainly didn't make my 35mm negative suddenly pop with enhanced sharpness/grittier grain.

[Drew Wiley]

You can also pique micro-contrast by using high quality Apo enlarging lenses, versus conventional ones.

[Bernard_L]

A good thread. For once, debunking a myth, instead of contributing to a myth.

[Corran]

Drew, maybe you can send me an APO-Whatzit to try out sometime .

The only lenses I use are EL-Nikkors, 50mm-150mm. I question whether my darkroom technique is good enough to get good value out of anything better.