Now it's hot here, my darkroom has 28 degree celcius. Just realized one weak point of motorized orbital: No way to use waterbath, so I cannot control developing temperature.
Perhaps I should develop with keeping tray in the waterbath and by rocking it... The motor is just - so ease.
A bit more about Orbital.
I got some time ago first negative that was developed unevenly. The edges of 4x5 negative had notably more density than other areas.
As this was real world photograph, I didn't measure it more, but I took some test negatives. Target was evenly illuminated wall from very close distance, camera focused on infinity.
What I found was significantly more density around the edges of the negatives. This was same with my both orbital tanks - one that has "dremel worked" and one that has silicon droplets.
Now, after I have looked issue more, I suspect that the cause could be change in the movement pattern.
My orbital used to rotate and tilt the tank. The tank rotated slowly on each turn of the motor base and got tilted on each turn (here's a youtube video).
Now it only does tilting movement, rotation is gone.
I haven't yet figured out what caused that and why my tanks have lost that rotation movement. Is there too much or too less friction?
How do your Orbital move with motor? Is the pattern similar like in the youtube video? If it is, then that is really the reason for my problems and I have to fix either motor base or go to the manual agitation.
This looks like too much agitation for me, and potential developer spill, although I know others use this method with no problems.
I used to fill with alot more solution so that the film is practically covered then agitate very gently by hand - similar to as you would with paper.
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The motorized agitation works at least up to 350ml when the lid is closed.
My guess is that rotation movement broke the developer flowing pattern and prevented uneven development.
Now when my motor base does not do rotation pattern any more, only tilts tank in (one direction) about 3 seconds intervals, it is just too much and flowing pattern istoo simple and predicable.
So it is like tilting towards every corner so that one full 'circle' takes circa 3 seconds.
Manual rocking surely works, but then my biggest fear is possible too strong development near the edges of the tank where moving developer bounces back.
Haven't done much testing with manual rocking though. However when doing traditional tray developing by rocking the tray, too strong edge density is often problem - like i have now with 'tilting only' motor base.
Last edited by Usagi; 08-13-2009 at 03:59 PM. Click to view previous post history.
Reason: typing errors...
Originally Posted by Usagi
Actually, I think you can. I have read reports of people dispensing with the motor or static base and floating the tray in a bath of water to maintain temperature.
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Here's video example how my orbital does agitation now. In the end of the video I use hand for doing rotating movement like my orbital used to do.
Which way is the proper for orbital with motorized base?
I also did some tests with much less developer and found out that uneven developing was not any more a problem. It seems that as I have slowly begun to use more and more developer (up to 300-350ml), it ruins the whole idea behind the orbital, which is to use only small amount of developer but move it fast over the surface.
Seems like 150ml is okay, perhaps 200ml also which I have used for a long time.
Still not sure about the proper agitation with motorized base...
For the last few weeks, I've taken to processing single sheets of 5x4 in the centre of the Paterson tray. I'm kinda hooked on the results of semistand development in 200ml of Perceptol at 1:4. Also getting good results on the motorised base, again with a single sheet & 160ml of dev.