Help! Film base colour and density isn't like the labs.

[jojo90]

Hi,

I've started developing C41 at home, mostly Portra and some Agfa Vista. I have issues with the resulting colour base of the film, and (I'm new to this) but what I would term 'density' which I take to mean that the film, when held up to a light, looking nice and contrasty.

My control is Agfa Vista 200/400. Essentially I've had this developed by two different labs and the base colour is a nice 'thick' orange colour (with a very very slight purple tint) and is the same from both labs. When I've been developing the same film stock at home (I bought in bulk, they all have the same expiry) my film looks like a very thin shade of orange, almost with a slightly brown tint. The negatives don't look very contrasty either (low density?).

My setup is as follows:

Rollei Digibase C41 with Jobo CPE2. I start my timers about 1-2 seconds after I start pouring in the chemicals, and start to pour out 10-15 seconds (depending on volume) before the timeframe end. All chemicals and washes are at 37.8 +/- 0.2 deg (dev is always going in at 37.8). This is measured using a digital medical thermometer. After adding the chemicals I 'rotate-invert' twice by hand, give the tank a firm tap on the worktop, then let pop it on the Jobo at speed setting 2 :

1) Pre-warm drum and film for 4-5 minutes.
2) Pre-wash for 3 mins.
3) Dev for 3:15 (I know to extend to 3:30 after x films)
4) Rinse 1 min
5) Bleach 4 minutes
6) Rinse 2 minutes
7) Fix 6:30
8) Rinse 4 min
9) Rinse 1 min
10 ) Stab 1 min

I'm a bit stumped really as to why the negatives are coming out differently to the labs. It's quite difficult to correct the colours when I scan them in (and it's never quite right, they have a very odd brown/orange tint). By comparison the lab developed film is really easy to colour correct.

When I developed my first film with this chemical mix the Digibase C41 instructions didn't mention a rinse between chemicals, so I didn't do it. The top of my tank blew off in the jobo after adding the bleach (I'm assuming it was reacting with the small amount of developer left in there, I had burped it and depressed the lid) so I googled and found most people were recommending a rinse between steps. I suppose there is a slight chance some developer has mixed into the bleach from that first run (or bleach into fix, etc) however it would only be a few ml. I tried to be accurate when mixing the chemicals as well, almost obsessively so!

I don't want to throw away all my chemicals just yet and make a new batch as the Digibase kit doesn't make the same amount of each chemical (as an imprecise example I can make say 5l of dev but only 1l of fix so if I throw away 500ml of fix I've cut the kit capacity in half!). I will however do this if people think I need to .

If it helps the colour base from my first 'explosion' run is the same as my most recent run, I'm still using the same chemicals as only 5 films into a 500ml batch.

Any ideas as to what usually causes a difference in the colour base of the negative? Does anyone know which step actually gives it the base colour and what variables influence it? Dev? Bleach? Maybe that would help...

Hopefully I've managed to upload an attachment to this post, this is a quick and dirty scan, film on the left is my effort, film on the right is the lab (scanned as RAW then converted without correction to JPEG). Both are Vista 200 from the same stock. All my home dev efforts have the same base colour. The difference looks much worse in real life however hopefully gives an example of what I'm referring to. I've only developed Portra at home however the film base colour is looking similar to the Vista, and scans don't look Portra like to me!

 

[Sirius Glass]

Wecome to APUG.

PE, Photo Engineer is the best one to answer your question.

 

[jojo90]

Thanks Sirius, I've reading posts on here started me off . I've added a scan to my 1st post!

 

[Sirius Glass]

That will help.

 

[bvy]

I wouldn't try too hard matching your film to something lab-developed -- unless you're using the same chemicals and machinery. It could be a futile exercise. As long as the color balance is something you can work with without having to dial in crazy filtrations (assuming you're printing), then that's really all that matter.

But if you're density isn't where you think it should be (all other things the same) then that's a problem. I use C-41 developer one-shot to get good, repeatable results. Trying to fix a problem -- especially a density problem -- by putting film after film through the same working developer also sounds kind of futile. Extending the time will help, but there's nothing like freshly mixed developer.

I would add an acid stop bath after your developer and before your first rinse. It won't improve your density, but it will put the brakes on development and extend the life of your bleach.

 

[Photo Engineer]

Try this: Just bleach a tiny piece of raw film for about 5' then wash 5' then fix 5' and then wash 5'. This can be done at room temp. Then after drying compare the color to the films in your post above. This should tell you something about the chemistry. The small clip test should be close to one or the other. If it is close to the factory processed example, then you have a process problem. If it is close to your example, then you have a different type of process problem. In the first case, it is likely in the prewet, dev, rinse portion and in the latter case it is with the bleach onward.

Now, here are some thoughts:

1. The prewet is WAY to long. Don't use more than 1' at 100F.
2. Never use a rinse after the developer. Either go into the bleach directly or use a 2% Acetic Acid stop.

PE

 

[jojo90]

Try this: Just bleach a tiny piece of raw film for about 5' then wash 5' then fix 5' and then wash 5'. This can be done at room temp. Then after drying compare the color to the films in your post above. This should tell you something about the chemistry. The small clip test should be close to one or the other. If it is close to the factory processed example, then you have a process problem. If it is close to your example, then you have a different type of process problem. In the first case, it is likely in the prewet, dev, rinse portion and in the latter case it is with the bleach onward.

Now, here are some thoughts:

1. The prewet is WAY to long. Don't use more than 1' at 100F.
2. Never use a rinse after the developer. Either go into the bleach directly or use a 2% Acetic Acid stop.

PE

Thank you for the advice, it's in the early hours here in the UK so I'll give it a go in the morning and post back the results. What I may also do is mix up a small amount of fresh bleach/fix and run the test to see if that tells me anything. I've updated my notebook on the prewet & to remove the rinse after dev, I should have a film finished in the next couple of days so hopefully I can nail that one based on locating the issue(s).

 

[Sirius Glass]

Keep good detailed notes.

 

[mts]

I always follow the developer with a sulfite-containing stop, then rinse before bleach. The proper pH of the developer, bleach, and fix are important as well. As noted above, if the films you process print or scan with reasonable corrections, then the mask is doing its job no matter how it might differ from what you got from a commercial lab. There is considerable variation in density and tone of the orange mask between different film manufacturers. Kodak Portra differs considerably from Fuji Pro 160S for example but colors are rendered rather well by both films. Should you have any further doubt concerning your or the lab's processing, shooting a few frames of the MacBeth color chart will assist. There is a difference in saturation resulting from exposure and you should bracket your exposures to evaluate this effect.

An afterthought, if you are seeing some difficulty in color correction you might be have a problem with retained silver, perhaps from weak fixer. Similar troubles are caused by formation of leuco-cyan dye which is a symptom of failing developer; check its pH.

 

[Rudeofus]

C-41 color developer is carefully balanced to gain optimal emulsion speed while keeping fog low. As soon as it is just a tiny bit off, you get either speed loss or fog. In my experience it takes just a tiny bit of pH increase to create foggy color negatives, and C-41 color developer (also the concentrate) will rise in pH as it ages. As you thoroughly prewash your strips, you also wash out certain compounds from the emulsion (stabilizers, oxidized developer scavengers), and this may well lead to increased fogging.

In my year long experimental phase with home brews, I never had underbleached negatives, but very frequently they were slightly (or not so slightly) fogged by color developer. It is good that you do that rebleach test PE suggested, just to be sure, but I would not put too much hope into it. Chances are they will both scan and print well, a bit of fog doesn't hurt that much.

If the fog doesn't go away with rebleach&refix, and if this fog really bothers you, you can try lowering color developer pH with Acetic Acid. You can test with a batch of C-41 process chems, a small bottle of Acetic Acid 10% and some small unexposed film strips:

1. Put a short test strip into a film tank
2. Process with prewash, color developer, stop bath, rinse, bleach, rinse, fix, rinse (don't bother with stabilizer)
3. Take out the test clip and compare it to lab processed strips.
4. If the test clip comes out foggy, add 2ml of Acetic Acid 10% per liter to your color developer (i.e. 0.5ml if you have 250ml process chems, 1.0 ml for 500ml, ...), proceed with step 1.
5. If the test clip comes out fog free, record the total amount of Acetic Acid you had to add.

PS: If you don't trust your bleach, you can try bleaching a fogged test clip in a strong Ferricyanide/Bromide bleach. This may do all kinds of stuff to your dyes (so don't do this to regular negs where you care about the image), but it will reliably bleach all silver.

 

[fotch]

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