Originally Posted by dbla
The only question you've answered is "what developer."
The only question you've answered is "what developer."
That appears to be something developed by the Jobo USA folks in Michigan after doing their own testing. It probably incorporates some "crap shoot" factor based on what was assumed to be a "typical" scene. It doesn't seem to deviate much from the 250ml stock per 80 square inches of film that's required for D-76 and many other non-XTOL developers.
Definitely, especially if one must contend with high ambient temperatures. The ability of XTOL to get by with 100ml of stock per 80 square inches of film means it can be diluted more, extending times so they're still long enough even when processing at 81 degrees F, which I'm forced to do in the summer here.
You could have used 350-400 w/no issues.
For 10 sheets 500 will work but if dilution is a worry, add a little more. This won't strain the motor and you can always move the 'crow's foot' out of the way and do a mono directional agitation. The results are the same and I've tested it with the densitometer I sold here. I've just moved to Bangkok and don't know where all my tests are to supply a visual aid so take my word for it.
I've switched to using mono directional agitation for all my large format (3005/3010) to reduce motor strain.
I was thinking more in terms of the rotational aspect of the expert drums with the developer draining from the tubes as they move towards the top of the drum and then refilling on the way back round. I'm guessing that at the normal speed the developer doesn't have time to drain off completely so that there is always some developer around and behind each sheet. With more sheets of film you would need more developer to cover the amount still adhering to each sheet. What I don't understand is why the minimums are lower for E6 and C41 (330ml for 10 sheets in a 3010) than for B&W (500ml for 10 sheets in a 3010).
For a good look at the developer's behavior in an Expert drum, watch this:
At normal rotational speed, it doesn't seem like the amount of chemistry that drains from a chamber would be impacted by the presence or absence of film. By the way, thanks for that video, Greg!
I have virtually zero knowledge about color chemistry, but your puzzlement supports my conjecture that Jobo's recommended minimums for black and white were based on developer capacity and testing. Color chemistry probably contains much more active ingredient per ml of concentrate.
Great, great info guys, thanks!
It just so happens I used up my last 1L packet of D-76 and recently got in a shipment of 10 5L Xtol kits ( have about 20 1 gallon D-76 packets for other films ).
I am moving to Xtol for my TMX anyway so this will be perfect...
I have increased my amount of chemistry lately and getting better negatives. With Xtol I use 50ml stock pr 4x5 sheet, that is double the minimum than Kodak suggests. If you go for the the absolute minimum you are not getting the best out of your negatives.
Had another thought about the minimum volumes required being different for colour and B&W. The concentration for the E6 and C41 kits is fixed, so perhaps the volume of the drum was designed around that, i.e. 330ml for 10 sheets is close to the minimum amount of chemistry for satisfactory development. With ID11 (my usual developer) the amount of straight developer required for 10 sheets of 4x5 is 250ml, which might be less than the volume required to properly cover the sheets during development. To get to 330ml the options would be to use 33% more straight developer than required or to dilute it. The first dilution factor with published times is 1:1, giving 500ml of chemistry. It might just be that enough of the usual B&W developers were the same so that it was easier to call 500ml the B&W minimum so that people could just use published times and dilutions. I'm sure there would be plenty of less experienced people who if told that 330ml was the right amount of chemistry would then tie themselves in knots trying to work out how to achieve that figure.
Nothing has changed in the two years since I wrote that post #6. Except for two-part vs. single-packet packaging, ID-11 = D-76.
That is not correct. 10 sheets = 200 square inches. 200 divided by 80 = 2.5 250 ml X 2.5 = 625 ml. The required quantity of undiluted ID-11 for 10 sheets 0f 4x5 is 625 ml.
Aside from the fact that 625 ml and not 330 ml is the right amount, why is achieving any specific quantity difficult? Mix the stock solution and use what's necessary!
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