DBI and Fogging

gbenaim · Aug 9, 2006

Hi All,

Just started doing DBI after reading Michael Smith's article, and have had some fogging. Most films turn out fine, but some do fog. I use FP-4 and HP-5 in 4x5, dev'd in Rodinal, and a 15w red light which I turn on 75% into full normal development. It's about 3 ft from the film, sometimes more. I sometimes have to look several times during the course of development, because I can't always see clearly the highlights. I read, however, in the AZO forum that it's hard to fog film even after several exposures to the light. Is this true only for pyro, or is it also true for other devs? Would the color of the light have anything to do w it, esp. w how easy it is to see the effects and therefore causing longer evaluation times? I usually look for 3-4 secs at a time. Would a green light make that much of a difference?
On another topic, emulsion up or down to prevent scratches? Thanks for the help,

GB

kwmullet · Aug 9, 2006

I'm far from an authority on DBI, but since no one's posted yet, I'll post soemthing to consider until a legitimate authority does.

Red v. Green has nothing to do with film sensitivity -- it's just that your eyes (well, most eyes) are more sensitive to green light, so given the same wattage and distance, you should be able to see more wth green than red.

3-4 secs seems a bit long. My understanding is that the tanning effect of Pyro desensitizes film the further into development you go, so there's less of a fogging danger with pyro than other developers.

The first several times I inspect, I only have the light on for about 1/3-1/2 a second. I just want to get an idea if the highlights have come in yet (looking at the base side). My last inspection or two as I'm about to make my decision to stop development probably runs a 1-2 seconds.

About the 15 watt red light. My guess is that that's probably way too bright. The Kodak dark green safelight filter is pretty darn dense. I've got a 15 watt bulb in mine and unless I look directly at the light, I wouldn't be able to tell it was on during the first minute or so I was dark. I'd say shoot for that level of dimness.

Also -- a fair amount of time can get lost juggling your film while reaching for a light switch. I suggest putting yours on a momentary foot switch.

I pull my film and put it in front of me where I'd want to inspect, then line the switch up under my foot, hit it for a half second or so, then release it.

good luck. DBI is very enjoyable and I find it much more reassuring than relying completely on time & temp.

-KwM-

gbenaim · Aug 9, 2006

Thanks, KwM

That's very helpful, actually, I didn't realize the green filter was that dim. Where can I buy one, and have it shipped overseas? Thanks.

kwmullet · Aug 9, 2006

I was very very lucky. I walked into the local brick and mortar camera store which greatly undervalues anything having to do with traditional film photography and got an old kodak green safelight (screw-in chassis with a bulb socket inside and a dark green glass filter) for about US$20-30, and a momentary footswitch off a gralab timer for US$1-2, if memory serves.

I believe this:
http://www.bhphotovideo.com/bnh/con...ls&Q=&sku=27655&is=REG&addedTroughType=search
is the filter I'm using. The safelight chassis would be separate.

Before you pop for one of those, though, check apug and michaelandpaula.com azo discussion board archives for threads about alternatives. I think some folks have been using green LEDs with some success.

-KwM-

gainer · Aug 10, 2006

Just to reiterate: panchromatic film has a much wider bandwidth than the eye. The yellow-green is the most sensitive part of the eye's spectrum. One will have to find the dimmest safelight you can find at the most sensitive part of the eye's vision because there no color at which you can see and the film cannot. Unless the film is orthochromatic.

Another ploy would be night-vision apparatus

jim appleyard · Aug 10, 2006

gainer said:
Another ploy would be night-vision apparatus

There was someone(s) here or at photo.net who did this and they thought it was great fun. A search for night vision goggles might turn up some info. IIRC, they are rather expensive and available thru hunting catalogs, military surplus, etc.

c6h6o3 · Aug 10, 2006

Use a green safelight with a 15 watt bulb. Keep the film a minimum of 3 ft. away from the safelight. Use a footswitch. Use pyro based developers, because the tanning action makes them inherently desensitizing. Look only at the base side.

Don't have the light on the film for any more than 5 seconds total no matter how many times you look at it. When the highlights begin to appear you will see them instantly. 1/2 to 1 second is all you should need for most glances.

Jim Noel · Aug 10, 2006

SInce you are having troubler seeing the image I suggest the fololowint.

Photograph a bright object large enough to fill about half of your image area. The reason for this is that it is easier to see a large highlight than a small one and when I learned DBA I had to get used to seeing the highlights.

Put your green safelight at least 4 feet from your film.
Use a pyrocatechol or pyrocatechin based developer.
When 2/3 or more of tthe estimated development time has elapsed, turn on the light for 2-3 seconds and look at the reflection on the BASE SIDE of your film.
When the film has developed enough to see the highlights as dark areas, it is adequate for silver printing. Of course, most of the alt processes require more time and this can be judged with experience.

FWIW - I have heard that inspection with a red safelight can be done with panchromatic film, but I have never trusted it. I use a 7 1/2 watt green safelight 4 feet from the developing tray and have not had afogging problem with any film.

It will take some time to get used to this method, but it is worth it.

Jim

jim appleyard · Aug 10, 2006

More reading here:http://unblinkingeye.com/Articles/Inspection/inspection.html

Charles Webb · Aug 10, 2006

Red for Orthochromatic, Green for Panchromatic. Has worked with any developer for more than 50 years. My favorites are HC 110, D76, DK50.

Since I pay attention to my exposure of the film, I have no need of compensating developers.

Charlie........................

gainer · Aug 11, 2006

Charles Webb said:
Red for Orthochromatic, Green for Panchromatic. Has worked with any developer for more than 50 years. My favorites are HC 110, D76, DK50.

Since I pay attention to my exposure of the film, I have no need of compensating developers.

Charlie........................

Not to stir up a fuss, but you seem to know something about compensation by development that I do not. My only use for compensating development would be to reduce negative contrast without LOSING shadow speed. I'm pretty sure you cannot control contrast by exposure alone. It can often be done by a combination of dilution, development time and agitation schedule, and most developers can be made to do it.

I think compensating development is more through technique than composition. We like to say "XYZTOL is a compensating developer" or even more obfuscatoryilly (Hey, my Dad was an English Professor), "ZYXTOL is a semi-compensating developer." "compensating" among photographers is much like what we used to call at NACA-NASA a weasel word. You try to use it in a report when you don't want it to let it be known you don't know exactly what you're talking about, but your branch head won't let you, and if he would, your division chief won't, and if he would the editorial committee of your peers won't, and if they would, the Technical Editing section won't.

Sorry, I'v been ill lately.

jim appleyard · Aug 11, 2006

Pat, hope your're feeeling better!

jim appleyard · Aug 11, 2006

Pat, hope you're feeeling better!

Photo Engineer · Aug 11, 2006

Patrick, I hope you are feeling better.

Here is a historical and technical note that Patrick, I'm sure is well aware of.

DBI was first used with slow unsensitized and ortho films. The safelight was red. As film speed increased and pan films became popular, green safelights were used and they were very dim. The faster films had to be treated in desensitizing solutions which were made up from pynacryptols.

In any case, today's modern films are not designed for DBI and do not respond well to desensitzing solutions due to the more robust dyes used in most films. (ever hear anyone complain about colored negatives after processing - some of the sensitizing dye was probably retained in the coating)

Anyhow, I'm not against DBI, I'm just saying that it is far more difficult to do using modern products, and if they become speedier, you may have to do as we did at EK for some products. We worked under IR illumination. The non IR films are not sensitive and you can have rather bright lighting, by comparison to any visible safelight.

Articles about this latter method may be found here on APUG.

Another safelight you might consider is the WR13 with a 7.5 or 15 watt bulb, about 6 ft away for a few seconds (indirect illumination only). This works with color paper, which has an ISO of about 25 - 100 to that lighting condition if you want a rough comparison.

PE

gainer · Aug 12, 2006

Thanks to all for your concern. A friend once said that when your arm is broken, your arm hurts; when your leg is broken, your leg hurts, but when you have a tooth ache you hurt all over. It was the extraction of a wisdom tooth and the associated molar. I had something like a stroke, but I still have more tests to go. I had never heard of the term "migrainous stroke" before. All I knew was that I would plan a sentence and try to say it, but the planned words did not come out, and worse, I knew they were not coming out. Imagine that you are talking gibberish and you KNOW it!

Again, thanks.

Scott Peters · Aug 12, 2006

I have not had issues with a green light 15W and pyro. I also look at the base side, but in some instances actually look through the other side. No problems with fog. The light is on for 3-4 seconds - about 3-4 feet. That's all you need. Start looking at around 75% - 80% normal development time. After awhile you will get the hang of it.

DBI and Fogging

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