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Guerilla darkroom 2020: hardware selection

Well, it’s been almost 20 years since I’ve did any updates on the original Guerilla Darkroom on the old site, so let’s bring things forward to this year. I’ll assume that the purpose of your darkroom work is getting to negatives for scanning, though almost all of this applies to regular printing.

Goal: get finished negatives. Do not scratch. Don’t go broke. Use what you have on hand. This part will deal with the equipment side. The next installment will cover chemicals and some finer points of (or really, cheats at, technique).

Special hardware

The three critical pieces of infrastructure that you do not have at home are (1) a developing tank and reels; (2) a changing bag; and (3) a thermometer. Let’s take these in turn.

First, get a Paterson Super System 4 tank. A new one (old ones tend to get chipped around the base, and their locking lugs may be loose). A Paterson Super System 4 developing set (tank, agitator, 2 reels) is $34 on Amazon. It’s hard to beat that. Consider that you may want to develop more than one roll of 120 at a time; realistically, this calls for a Multi-Reel 5 or larger.

Don’t screw around with Samigon/AP/Arista clones of older Paterson System 4 stuff.

  • Old-style tanks are not much cheaper.
  • Old-style tanks share the vice of older System 4 tanks: using a gasket to seal, being really easy to cross-thread, and therefore leaking all the time. Super System 4 uses a rubber cap over the whole top, and its funnel/light trap bayonets in.
  • Super System 4 can be agitated using a key that fits through the hole in the “funnel.” This is like having a vertical Jobo.

Do not complain about how much tanks cost. Film photography is expensive. It is a luxury good. You picked this path. Tanks are a critical piece of the developing puzzle.

Steel tanks are functional and use less liquid, but they require a lot more skill in loading film onto their reels. The big argument for steel has been that plastic reels degrade over time. That’s not borne out by my experience; I have some plastic reels that are 20 years old now – and still reliably load 120 film. It all boils down to keeping the ball-bearings clean and not warping the reels through hot water or abuse. Steel reels also are single-size: so you have reels for 35mm and reels for 120, and never do the twain meet.

As to reels, there is little to recommend actual Paterson-brand reels (except that they are basically free with the Paterson kit pictured above). Any compatible type will work, with Samigon/AP/Arista reels being slightly less nice but having a slight edge for newbies because they have loading ramps. Note that with these ramps, you will have to separate the two halves of the reel to safely remove the developed film. With no ramps, you can flex it out if careful.

Second, get a big changing bag. You will use this in lieu of a darkroom for film work. Some bags at Adorama, for example, can hold a Paterson 8-reel tank. To be frank, there is nothing to recommend finding an actual dark room. The inevitable result is that you notice little pinhole light leaks and freak out. Or you get disoriented and misplace things. With a changing bag, you are no worse off for not being able to see what you are doing, plus you can watch television while you load reels. Just don’t wear your Apple Watch or your tritium-lumed vintage watch. Actually, you shouldn’t do that in any circumstance where you are loading film into tanks.

Do not waste time trying to improvise a changing bag. Yes, there are Depression-era guides that tell you that they can be fashioned from sweatshirts, etc., but film had a much lower speed back then, and if you get light-struck film, you waste all of the efforts you made shooting pictures in the first place.

Finally, get a good glass thermometer that can go several degrees above or below 20C and has fractional gradations (recommended: Paterson PTP381, 15C to 65C). Metal thermometers are sometimes hard to read, can fog up, and never seem to be as accurate. You won’t break the glass thermo as long as you keep it in its square-profile tube. This is $25-30 well spent, since an accurate thermometer can mean the difference between usable and unusable negatives. Overly dense negatives are not fun for printing and really not fun for scanning.

Other hardware (not so specialized)

Timer. Could be anything that can be set for a time between 1 and 7 minutes. LCD kitchen timers are great. Anything that disappears when not stimulated (like the iPhone clock app) is not. Try getting that phone unlocked with wet hands. The Massive Dev Chart app has timers built in. And noises. And klaxons. We’re easily amused.

Film leader retriever. This can be used for two different operations. One, you can retrieve and trim the leader square at the end (if you bulk load film, and your camera has a rubberized takeup spool, you may have just left it square). Bonus points for rounding the corners to make the film load smoother into the reel. Two, you can pull all the film out of the cartridge, which obviates opening the cartridge (generally something you would do with a bottle opener – caps are crimped on really, really hard). Many people reload commercial cartridges by leaving a little film out and attaching the new film to that. Here is the Ars Imago (B&H house brand?) version ($10), which is the latest knockoff of the classic:

Scissors. You can use any household scissors. I would recommend something sharp that cuts straight. So not pinking shears.

Measuring vessel. A 1000ml graduated cylinder is customary. If you use HC-110, gradation in ounces may be more practical (since you mix 4 oz of developer to 124oz water to get 1+31, i.e., dilution B). If you want to see a real artifact of the past, some British grads have imperial ounces as well as US ounces and mL.

If you want to get really lazy, you can measure exactly 1 gallon of water into your storage bottle (or 4L, etc.) and mark with a line where the water level is. Dump out the water. From then on, you only measure the concentrated developer and simply fill with water to the line. Surprisingly, or maybe not, the width of a chisel-tip marker line is precise enough. Make sure you use this special bottle on a level surface.

Storage bottles. Bad news here: the thin 1-gallon bottles used for distilled water make really poor darkroom storage bottles. They do not seal well, and the thin plastic is permeable to oxygen. That said, if you are not storing chemicals for more than a month, no problem. Eventually, you will want to save any 1 gallon or 5 liter bottle from store-bought photo chemicals and repurpose it for storage of diluted chemicals. For example, I have an old Photographers Formulary TF-4 concentrate bottle that I user to store diluted Ilford fixer.

Dump bottles. Your life will be a lot more fun if you can quickly dump chemicals when you change stages of developing. The dollar store had some cylindrical 1-gallon cereal containers marked off in liters and fractions of a gallon. With a 20cm opening, these can catch your dumped chemicals. Key qualities of a dump bottle:

  • Has a wide mouth so that a tank inverted above it will dump straight down.
  • Holds at least 2.5L of liquid – the capacity of the biggest developing tank – and preferably a gallon – 3.8L – because you can also use it to mix chemicals. Try stirring chemicals through the opening on a milk jug.
  • Has straight sides.
  • Has something to hold onto (like indentations) and is not slippery. Developer is basic (not acidic), and you will find that like soap, it makes everything it touches slick.

These do not need elaborate seals or even really to be airtight because you are not using these to store chemicals. Having lids is preferable

Kitchen-type funnel. You already have this, though I don’t recommend using it for food or drink thereafter. If you have a spare Paterson “cone” for a developing tank, that also makes a good funnel.

Drying rack. For rolls of 24 frames or 120 film, you might find that a rolling laundry rack with a “grid” style top shelf is very practical (if you already have one). You can clothespin the film to the grid, and use more clothespins to weight the film ends. Film does not curl as aggressively as it used to, so you don’t need weights.

If you don’t have a rack like this, your “top” can be made from a two-clip trouser hanger that you already have in your closet – and hung off whatever is convenient (overhead pipes, usually).

36 frames of film require a lot of space and long arms. This requires being hung from the ceiling.

Not critical.

There are several things you can dispense with:

  1. Squeegees. These come packed with some older developing sets. They can be used to dry film faster. They are also good at scratching film if you don’t keep them clean. With the right wetting agent and a not-too-dry environment, film dries on its own in about an hour anyway.
  2. Weighted film clips. Not really needed.
  3. Hose-type rinsing attachments. If you use hypo-clear, the wash time for 35mm is not very long anyway. Plus these attachments tend not to fit any modern faucet. The longer you run water, the more likely you will have a temperature transient that can ruin your film.
  4. Forced-air dryers. If you are a photojournalist in 1965, and you have to rush out that print for the rotogravure section. yes. Otherwise, they are space- and energy-intensive. And are actually frustratingly slow.
  5. Sous vide heaters. Much the rage for color, if your bent is black-and-white, you don’t need any artificial temperature control. I’m as much a fan as anyone of using kitchen tools, but you can leave this one alone.

Punching your way into film identification

So the usual has happened. You have a pile of undeveloped film. Maybe you didn’t note the processing (N, N+1, N+2) or maybe it’s bulk loaded film that has no label on the cassette (for example, you might find it very easy to confuse Ilford Pan F Plus 50 with Ultrafine Xtreme 400). Or you can’t remember what order you shot film. Of course, the difficulty is that unless you somehow identify the film canisters, you’ll mix things up. And even then, once film is out of the canister and developed, there is rarely a persistent indicator of what happened. Data backs for 35mm cameras are something of a pain, they don’t record everything, and almost all of them are going extinct in 2018. Buy a Nikon F6 that records exif data? It’s a little late in the game for that.

The solution: the $5 arts & crafts hole punch and a $5 film-leader puller

One perhaps non-obvious solution is to permanently mark the film leader. You obviously can’t do this with a pen because the writeable part of the film will get washed off in processing.

The most effective way I have found to achieve this is with craft hole punches, which come in various hole sizes (1/16, 1/8, and 1/4″ – 1.5mm, 3mm, or 6mm), as well as a variety of shapes (round, hearts, stars, diamonds). As long as you make the marks on a part of the leader that will not be discarded (so not the long thin tongue part on commercially loaded film), these will survive the development process and won’t go anywhere until you snip them off. The uses are numerous:

— Bulk-loaded film: If you punch the leaders with a distinctive mark, you can avoid mistaking one type of film for another. For example, where it is very easy to confuse bulk-loaded Ultrafine Xtreme 400 and Ilford Pan F Plus, punching the Ultrafine with a heart will help you avoid mixing things up when loading your camera.

— Processing regime: If you are going to push-process film, punching the leader with a mark (such as a star) either before or after exposure will help prevent you from mixing up your N, N+1, and N+2 films. If you need to, you can use a leader-retriever to pull the leader out and mark it after fully rewinding.

— Order the film is shot: If you can’t imprint the first frame of a roll with a data back, you can use a number of punches to signify the order in which the roll is shot. You can even do this before you shoot the film.

— Camera or lens used: no data back records focal length, and camera bodies of the same make – assuming they even have a film-gate cutout for identification – use the same cutout (for example, Konica bodies usually have a triangle notched into the edge of each frame).

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Taming the Durst AC800

Ok, you bought a Durst AC800 or AC800 Elite for black and white work – so now what?  The good news is that your unit’s memory is probably blank.  The AC800 series used a soldered-in Nicad to hold its memory settings.  More than 20 years after production, it’s unlikely that your unit will hold its settings unplugged for more than a day or two. But since it’s probably unlikely that you (or the previous owner) ever correctly understood the Allemainglish directions, you’re not losing much.

This is best I could come up with via trial and error.  Use calibration data at your own risk.

What the hell is an AC800?

An AC800 was pretty much the last thing before minilabs.  It is a 6x9cm enlarger with two color densitometers (one reading negatives and one positives) that was capable of self-calibrating and auto-correcting color prints from negatives and slides.  It cost about $15,000 new.  It was usually paired with an auto-advance roll-paper easel so you could really crank out the prints.  The AC800 Elite was the same thing, with autofocus.

Most AC800s that did not hit the scrap heap are being pressed into service printing black and white photos.  For this purpose they are overkill – but it is far easier to get an AC800 than an M805 or any other quality 6×9 enlarger.  Dursts have solid metal chasses and are pretty much immune to misalignment.  They make everything else look like a cheap, crudely-engineered toy.

The AC800 uses a different theory of metering, namely offsets in terms of density units (30 units = 1 stop).  In essence, you can translate real-world density adjustments directly from an external densitometer or step wedge directly into the machine.  Although this may seem strange at first to people used to using conventional timers with conventional enlargers, it is actually a lot more intuitive.  The AC800 is designed to get you a proof-quality print on the first try, no test strips.  From there, you fine-adjust the filtration or change the contrast to suit.  The AC800 needs to know what aperture it was calibrated at; from then on, if you tell it the aperture you are using, it will auto-compensate the exposure for that aperture.

Behind the scenes, the AC800 uses additive filters (R,G,B) to approximate subtractive (C,Y,M,K) filtration.  It uses its dichro filters both for color and neutral-density purposes.  For this reason, it is important to foget about the use of these filters to approximate multigrade filters.  In color mode, the machine will expose different colors for different times – something that just doesn’t work for multigrade paper.


Don’t worry about expensive Durst COLAMP bulbs.  Get the cheap GE 24V/250W equivalents.  For b/w work, you don’t need color-calibrated bulbs.

The original carrier for this enlarger is COBINEG with a glassless BIMANEG carrier top and bottom (top has square sides, bottom has beveled, though you can use either in either position).  You can also use a BIMAGLA-AN on the top and/or a BIMAGLA on the bottom.  The AN glass of the BIMAGLA-AN will eliminate the need for most dust-spotting.

Since COBINEG is just a BIMANEG (M805 carrier) minus the masking blades, you can use a BIMANEG.  Just make sure that the masking blades are retracted when doing any type of calibration.  They can also skew the exposure if they impede too much into the frame.

The 6×9 mixing box is all you need.  You can get the 35mm or 6×6, and pay a lot for either, but your exposures will become painfully short. When used with 35mm film, the 6×9 box also helps diffuse things a little more, overcoming the inherent 35mm dust problem.

For lenses, you should use a 50, 80 and 100 with the AF version.  For the plain AC800, you can use 40s instead of 50s and 90s instead of 80s or 100s. I would recommend getting some hot glass, since this is a diffusion enlarger.  Lenses go on flat flanges for 100mm, semi-recessed for 80mm, and recessed for 50mm.  You can use the circular disk boards common to most Durst enlargers.

Understanding the memory of a machine

You must remember that this enlarger has four memories (well, you wouldn’t remmeber this because the instructions are terrible at explaining this).

CALIBRATION – this is long-term.  This is the baseline for each channel, and it stays in place until changed by the user or until the power is cut and the battery backup dies.

PRODUCTION – this is short term.  This treats the calibration value as the “zero” point and adds on.  This will re-zero between prints unless [HOLD] is lit.  This is the value that is shown on the 3-digit display when you are making prints.

BASE – this is medium term. If you hit [ENTER] + [SETUP] in production mode, the Production correction (on the numeric display) will be added to the calibration (temporarily), a dot will appear on the numeric display, and the numeric display will go to zero.  This is useful for changing to a paper that is, say, a stop slower.  Base memory gets erased if you change channels or turn off the enlarger.  This is useful if, say, your total density correction exceeds 99 units.  You could put up to 99 on the production, move that into base, and add another 99 to production.

HEAD – under the little sliding cover on the side is a fourth, hardware memory – this is the basic calibration to cancel the orange film base with color film.  Do not mess with this, ever.  Not only is it pointless to do so with b/w printing; you could also break the filter mechanism.  This is adjusted with the strange little ferrule tool that sits in a hole in the enlarger base.

Basic b/w calibration for multicontrast paper

First, get it out of your head that you are going to use the built-in dichro filters for multicontrast b/w work.  It just won’t work.  Those filters are designed to automatically deploy for color film, and the filtration values will not hold constant to recreate your favorite polycontrast settings.

Turn on the unit with a carrier in but no negative inserted.  You will see an R-G-B test sequence.  This allows the transmission densitometer to take a baseline reading.  At the same time, the reflection densitometer (on the side of the head) takes a baseline reading of an 18% grey reference (make sure you have a piece of grey card under there).

Switch the unit into b/w by pressing [ENTER]+[CHANNEL].  In this mode, the enlarger will use only yellow light to expose paper.

Here is the calibration method.  This will illustrate grade 0 paper assigned to channel 0.

1.  Make a 0,7 density negative (base plus exposure).  If you have the color calibration negs for this enlarger, they are not useful for this purpose.  Bracket a roll of film of a blank white wall, -2 to +2 exposure, in as small steps as you can.  Zero a densitometer (like a Getrag) on the film base, and then pick the negative that reads 0,7.  Note which negative it is.  The negative should be no smaller than 6×4.5.  The enlarger only reads the center 24x24mm, but you should have some margin.  Put this negative in the carrier.  You only need to make one negative for all channels.  You could conceivably also use a representative negative.

2. Cut a piece of the #0 filter to fit on top of the negative carrier.  Insert the negative carrier.  Set the lens to f/8 (“working aperture”)

3.  Press the [HOLD] button on the head.  This will assure that any corrections you will make will not disappear after your exposure.

4.  Expose a piece of paper.  Develop it.  Compare it to a grey card.

5.  If it is lighter than a grey card, press [DISP] until you see the D value and increase it.  30 units is one stop.  Likewise, if it is too dark, decrease the d value.

The unit actually has a closed-loop self-calibration (expose, show the print to the reflection densitometer, repeat until the D number is stable), but you will drive yourself up the wall trying to get it to work.  This method is simpler, is a one-time operation, and gets you results just as close.

6.  When you have the D number that gets you the right print density, record that number on a piece of paper.  Then press [+] and [-] simultaneously to zero the D setting.  This last part is important.

7.  Press setup. Using [+] and [-], input the lens value.  Then press [ENTER].  Then input your working aperture (see #2) and press [ENTER].  Then input the D value you recorded in #6.  Then press [ENTER] + [SETUP].  The enlarger will read the negative and lock that D value into the memory for that channel.  Press [SETUP] until the setup light goes off.  You don’t need to set XCP, LN and DN because b/w negatives and paper don’t have the same reciprocity issues that color does.

8.  For subsequent channels and grades (1-3), you want to achieve exposure times roughly equal to the exposure time for grade zero.  So on Channel 0 with the 0 filter in, press the [LIGHT] button on the enlarger.  Press [DISPLAY] until you see the Ey value.  This is the exposure time in seconds.  Mark this down.  Press [LIGHT] to turn off the lamp.

[Light] turns on the head with filtration activated.  [W. Light] provides no filtration, just what is set in the HEAD adjustment.  There is no practical difference.

9.  Next, put the #1 filter in.  Hit [LIGHT] and take a look at the Ey value.  Press display and move the D value up or down until Ey for #1 is the same as Ey for #0.  Mark this down.

10.  Next, do  the same for #2.

11.  Next, do the same for #3.

12.  For #4 and #5, try to get to values that is about double the Ey of grades 0-3.  This gets you into the right ballpark for the speed loss associated with grades 4-5 (usually half the paper speed).  Multicontrast filters affect film speed – it is not like using the 2-filter method with a dichro head.

Why are we trying to get to even exposure times?  Because you are using a color lightmeter to measure a monochrome negative plus a colored filter. The procedure above helps filter out the metering errors caused by using pink and yellow filters when you are using only the yellow channel to meter.

13.  Plug these values into the setup sequence for each filter (#7).  Make sure that the right filter for the channel is above the negative when you program these in.  And make sure the production D is 0 before initiating the setup sequence.  Otherwise, that value can screw up the calibration.

At this point, you should be able to run a series of test prints across grades that will be a consistent grey to within about 10 density units (1/3 stop).  You can agonize further and fine-tune the calibration numbers until they are all perfectly visually identical, but the reality is that changing paper grades will almost always necessitate changing the production D setting by about that much.  And the two emulsions of Ilford MGIV appear to be very slightly different colors, so there is a point of diminishing marginal return. 

14.  Once you get this whole process under control, go through each channel in [SETUP], hitting enter through the values until you can write down the D value for each channel.  If you do that and experience memory loss, all you need to do is repeat step 13.