A couple of C-41 questions

[robert_davis2]

C-41 is aimed at machine processing. I know the C-41 manual Z-131

mentions including the drain time into the 3:15 developer step. How

much will I notice if I just ignore the 10seconds or so it takes to

drain? In other words. I develop for 3:15 then drain then stop.

Basically I'll have a short push?

 

The other question. I guess it's impossible to make my own control strips?

[steve_levine]

I wouldnt run with too much of an "off timed developer bath".Once you adjust your meter to this,you will have trouble getting outside processing done.However,I dont think 10 secs is all that much difference?Control strips are exposed by very expensive sensitometer controlled machines.Using a camera or other imprecise method to expose these ,would be a waste of time.You can shoot a gray card at various exposures to check density(between batches),but shutter inconsistancies will destroy any ability to compare different densities to each other.(The latter being the method used to plot a curve).

[rowland_mowrey]

Yes, you will have a short push if you don't include drain time in the developer time. With my Jobo processor it takes me 8 seconds to drain the normal amount for 35 mm or 120. For large quantities of film with 1 liter or more of deveoper it takes me 15 seconds for the drain. That could equal a full push.

 

Making control strips is not very hard if you accept the fact that they are not 'real' control strips. The following will be useful though.

 

Take a picture of a MacBeth color checker or a similar color and neutral step scale at the head and tail of each roll of film with identical lighting.

 

When you process the film, you will have a sort of built in check for the film age, latent image, and process. This works out very well. Especially if you do it with fresh film, with fresh exposures, and process a roll like that every once in a while to keep track of the 'real' appearance of the chart without any keeping. Then any difference is due to the process.

 

I usually do this every time I change batches of developer, and sometimes in between batches. When I proof the roll, I can see the chart and netural giving me extra information on the process.

 

If I take one at the head and tail of a roll, it clues me in as to end-to-end uniformity of the processing of my film which comes in handy sometimes.

 

Hope that helps.

 

Ron Mowrey

[robert_davis2]

So basically just check if the colours are right on the frame with the colour chart? Would it make sense to shoot a grey card to and check the frame with the densiometer?

 

One more question-) Is it possible to over bleach/fix? The chemicals I picked up seem to be some rapid C-41. The instructions call for relatively short bleach/fix times. I'd feel better going with times more in line with normal C-41. From reading the little info I could find on rapid C-41 it requires more agitation for the bleach and fixer then normal C-41. Would just using the longer times make up for this?

[rowland_mowrey]

Robert;

 

A grey card gives you one point and no information about possible curve crossover caused by a bad film or process. A grey step scale gives you several points along the curve.

 

As one person here put it.. Some manufacturers processing kits are a 'bad hack' so depending on kit, you can over bleach or over bleach-fix and hurt the film or paper.

 

With Kodak bleach, it is very hard to overbleach.

 

Ron Mowrey

[robert_davis2]

What happened was a local lab upgraded thier equipment. The new setup doesn't take mixed chemicals. It's more like printer toner. He plugs in a bottle and that's it. Great in some ways but it left him with all this fuji-hunt stuff that wouldn't fit his machine. Well he offered. I helped him out by cleaning the back room out-)

 

Thanks for all the help.

[georg_kern]

You mentioned a "stop" after the developing. Be careful with this, because C41 developer seems to have high concentrations in carbonate (please correct me, Mr. Mowrey), which gasses out when brought into contact with an acidic stop bath and destroys the emulsion. Some films are more sensitive to this than others (gelatine hardened to a differnt degree); You can ruin your film by doing so (at least I did it). Another hint: it is difficult to 100% duplicate a machine process in hand-processing. So: start with the recommended times and temperatures, check your results (best done by visual examination of contrast of the prints, because contrast changes much quicker in C41 than density) and then adjust your process by changing the developing time in +/- 10 seconds or temperature by +/- 0,5 degrees. Once it works, keep your workflow as constant as possible.

 

Regards

 

Georg

[robert_davis2]

The developer I use is:

 

Water (Room Temp) 800.0ml

 

Potassium Carbonate 32.0g

 

Sodium Sulfite 3.5g

 

Potassium Bromide 1.5g

 

Hydroxylamine Sulfate 2.0g

 

CD-4 5.0g

 

Water to make 1.0L

 

Steps are

 

Developer

 

Stop

 

Wash

 

Bleach

 

Wash

 

Fix

 

Wash

 

Stablizer

 

I'm using a weak stop. About 1%. The negatives are very colourful. I just need to print them and see.

[rowland_mowrey]

Robert;

 

Please be careful using the stop after development. It can cause problems. C41 films are designed to go directly into the bleach and besides the production of carbon dioxide due to reaction of the acetic acid with sodium carbonate, the extra acid can degrade the dyes due to pH.

 

Also, the developer formula you have is just 'approximate' compared to C41. Several ingredients are either missing or at the wrong level so please don't be surprised if the results don't match up to your expectations or to commercially produced negatives.

 

Ron Mowrey

[robert_davis2]

The stop and wash was suggested to deal with reels instead of the a commerical machine with squeeges. It'll cut down on the developer carry over. It keeps the bleach from going bad too quickly.

 

The formula supposedly started out in Zone V.

 

I'm actually kind of suprised how good everything came out. I had a test roll processed by a local lab and I think mine look better. OTOH the proof is in the printing. Hopefully this weekend I'll have a chance.

[Bill C]

Robert, if you really want to match a commercial process, you might just ask your mini-lab guy if you could have (or buy) a couple of his control strips. Then, process one along with your normal run.

 

In case you don't know how the control strips work, these are typically available from people like Kodak, Fuji, Konica, etc. What they do is expose the control strips under tightly controlled situations. Then, from a batch of strips, they process one in their own tightly controlled process. This processed strip is a reference for the user; it reflects an aim point. Note: in reality, these are never perfect, so a set of density correction values are also included. So basically, you would process one control strip, then take it back to the minilab and read certain densities with their densitometer. Then, you read their reference strip and apply correction values. Finally, compare your results with the corrected reference strip.

 

So basically, if you had one test patch that read, say 0.65 red filter density, and the reference strip read, say 0.75 with a -0.03 correction, you would be 0.07 below the 0.72 aim point. If you're on good terms with the lab, they'll show you what to read (insist on reading the reference yourself; that way you don't need to confirm densitometer calibration).

 

As a rule of thumb, if most "plotted" points are within 0.05, you are pretty close to aims. If you exceed about 0.10 away from aims, these are probably outside of spec limits.

 

Personally, I think it's very unlikely you'll be that close; however, you can probably tweak your developing time to get close. Assuming, that is, that you even want to match the commercial process. If you're getting along fine as is, that's probably good enough; I would just say don't do commercial work if you're not sure you're meeting the specs.

 

Since you don't have a calcium sequestering agent (anti-cal, etc), you should probably make sure your mix water is really clean (like D-I or distilled).

 

PS; for homemade control strips, I would suggest this: shoot an entire roll or two of a test target, like Macbeth card. Let these sit for a couple of days to let latent image shift settle down. On a processing run, use one commercial control strip plus several randomly selected samples of your test shot (several of yours to check that your exposures are consistent). If the commercial one is close to spec, yours can become your new standard. Throw the rest of yours into the freezer; when you want to check your process, pull one out and process with your regular work. In the freezer, they're good for a long period of time; probably 6 months or more.

[robert_davis2]

I'm using distilled water to mix all the C-41 chemicals. Our tap water is almost pure calcium carbonate-). I'm just doing it for myself. If I can print the stuff easily then I'll be happy. It took less time to process a tank of film then it would have for me to drive into the city and drop off the film. 35mm is easy enough to get done nearby but it gets harder for the other formats.

 

I've got a colour densiometer [it's ancient but working] problem is last time I looked control strips only came in fairly large batches. That wouldn't be too bad but my understanding is they don't keep very well.

[Bill C]

>> ...but my understanding is they don't keep very well. <<

 

No, they should keep pretty well in a cold freezer.

 

 

>> ...last time I looked control strips only came in fairly large batches. <<

 

Actually, that's why I suggested beg or buy a couple from your 1-hour lab guy.

 

Here's another suggestion: as Rowland suggested, shoot a couple Macbeth targets on a roll of film. Then, have this commercially processed. If, before the commercial processing, you were to clip off a foot or two of the leading edge, you can process bits of this in your own process as a reference. Again, freezing the strip is the standard method of minimizing latent image changes.

 

Like you said, if you can print the stuff easily, you'll be happy. However, it's possible that your process is significantly off; in this case, a significant improvement might be possible. So some kind of verification of this is probably a good thing.

[robert_davis2]

I checked the B&H website and a package of 50 strips isn't too expensive. Assuming the local lab supply place is in line I think I'll order a box. How long will they keep in the freezer? Kodak talks about 0F. My freezer isn't quite that low.

[rowland_mowrey]

The 0 deg F freezer is recommended for storing film test strips. I use it for all of my film. Film stored that way will just about double or triple lifetime.

 

You have to be careful of moisture condensing out on the film if you open the package too soon after removing them from the freezer.

 

I find that my process, using commercial chemicals, is within 0.1 log e or better in color balance and speed. The point here is that control strips are intended for tracking seasoned processes. If you use throw away developer, then there is no seasoning problem or error accumulation due to replenishment, therefore control strips merely test your temperature control and agitaion, as well as timing. Seasoning factors are by far the biggest thing to deal with in any photographic process. You can usually do a very good job with temp, agitation, and timing.

 

Of course, mixing it yourself throws in an entirely new factor.

 

Good luck.

 

Ron Mowrey

[robert_davis2]

My timing,agitation and temp control are all handled by a machine of one sort or other. So I'd gain nothing from the control strips? Or would it let me judge if I need shorter/longer times?

 

I'm reading the Z-131 document on control strips and it seems like it might be useful. But then what do I know-) I'm just hoping I find the time to make a print this week.

[rowland_mowrey]

Yes. Control strips would let you know if your process was 'hot' or 'cold' so to speak.

 

It wouldn't tell you what specifically was wrong though. It could be time, temperature, agitation, or chemistry.

 

Although the first 3 tend to influence contrast and density and the last tends to influence crossover and color balance, that is such a generalization it is almost meaningless.

 

Sorry I can't be more helpful.

 

Ron Mowrey

[Bill C]

>> So I'd gain nothing from the control strips? Or would it let me judge if I need shorter/longer times? <<

 

Robert, without some sort of reference point, I don't believe you can have much idea where your process stands.

 

Basically, for your purposes the control strip will tell if your process is "hot" or "cold", as Ron said. Since you've been looking at Z-131, notice what happens in the sample plots. Start by looking only at the LD (low density) patch plot as this is the most straightforward.

 

For the most part, you should see that things which affect the "activity", so to speak, of the development process will act similarly: as the activity increases, the blue plot (amount of yellow dye formed) goes up the fastest, followed by the green and lastly the red. And when activity is going down, the LD blue drops fastest, then green, then red.

 

So if, for example, you found that your LD blue was -20, green -15 and red -5, I would suggest you increase either your time or your temperature a bit. Not because you KNOW these are wrong, but because this is the easiest thing for you to adjust. Here's an example: maybe your developer pH is too low; a control strip plot would look similar to a short time or low temperature. And you could largely correct it by increasing time or temperature.

 

Robert, I've tried to gently steer you away from buying $50 (or so) + shipping (they'll probably come packed in dry ice) of control strips. You may not be happy with how the plots look. So again, I'd suggest just get a couple from the local lab and see what you think

[Bill C]

>> The point here is that control strips are intended for tracking seasoned processes. <<

 

Ron, definitely I agree this is a major use of control strips using a statistical method. However, in another sense, control strips are probably a manufacturer's best method of communicating the desired level of activity of a process to the users. They can change this over time, if desired, by biasing the control strips. So even if a processor uses another brand of chemicals, that processor will make adjustments to put the control strip plots within aim.

 

Basically, Robert IS that processor.

 

Alternatively, Robert may not care if he matches the manufacturer's aims as long as he gets nice looking prints. But if I were in his place, I'd just like to know how close I was to spec.

 

Regarding the exact chemical formulas, I'm not sure how crucial that is to a person like Robert. I can appreciate that careful testing and evaluation has been done on specific films and the chemical processes for them. However, in a replenished system in the real world, the films being put through a process all contribute to the makeup of the developer (various DIRs and what not). So various byproducts from one make of film can affect the processed result of another type film. For example, a replenished Kodak C-41 system running only Portra film would produce a certain response in the film; however, if 2/3 of the customers switched to a Fuji pro film, I'm pretty confident that the remaining 1/3 Portra customers would have measureable changes in the film results (the photographer might not see changes; however I'm pretty sure sensitometric testing would show such). Obviously, these would not be too drastic as trade trials would have revealed such during product development.

 

So with this in mind, I think slight formula errors in Robert's mix may not be any worse. I don't know for sure, though. At any rate, I'm not sure what he could do better (except buy the real McCoy); he doesn't have any way of knowing what the real C-41 formulas are, and those who might know are not at liberty to reveal it.

[robert_davis2]

"Robert, I've tried to gently steer you away from buying $50 (or so) + shipping (they'll probably come packed in dry ice) of control strips. You may not be happy with how the plots look. So again, I'd suggest just get a couple from the local lab and see what you think"

 

No I understood. It's just easier to order a box from the local distributor. B&H shows the small 25 strip Kodak ones for only $20. The local high priced retailer is only marginally higher for the Fuji 30 strip box so I'm hoping the distributor is cheaper. I assume they both work the same. The other thing is I need to order some film from the distributor. The bigger my total order the better deal they offer.

[Bill C]

>> I assume they both [Kodak vs Fuji control strips] work the same. <<

 

Actually they'll probably differ more than you would expect. I've known of cases where someone couldn't get everything into the spec limits, but on switching brands of control strip, found everything came together ok.

 

I guess the ideal situation is that you'd use control strips from the manufacturer of your workhorse film. If you get roughly within the spec limits, trying to look too much closer might drive you crazy.

 

Hope you have fun with the testing. I'd be interested in hearing, just for kicks, how close your process was running.

[robert_davis2]

Well I use mostly Kodak Portra but just picked up almost 40 rolls of Fuji Superia on sale. Then I've got Optima II in the fridge. Not to mention the cheap Konica I picked up to learn processing on. At least I'm only using two kinds of paper-)

 

I need to print these negatives before I process any more film but then I'll try and get some control strips. I'll try and remember to report back.

[robert_davis2]

I'm just back from printing the first few prints. I set the enlarger at the exact same colour filtration. Intially I did a test strip to get the times but that showed the same 9 seconds I've always needed with good negatives. All I can say is wow-) At least so far. No changes in the filters needed. The prints look wow-)

 

Thanks everybody.