DIY 4x5: Uneven dev/agitation vs light leak in tube

[singerb]

Hi all,

I'm starting to do my own 4x5 development with a tube/valve system in 1.5" PVC pipe, and have a few questions.

1) My first attempt ended up with nice overlapping parabola shaped areas at one end of the film. My assumption was that this was due to uneven development, since I rested the tube at an angle in between agitations. Is that correct? That first attempt, I agitated like a I do for my smaller format daylight tanks; at the start of each minute.

2) Next try, I did constant slow twisting/tilting agitation, and had none of the parabolas. I did have what looked like a light leak, but since the camera is also homemade (pinhole) I couldn't be sure where it was coming from. However, it did look like the light leak I had on my first frame from that camera (lab developed), but just to make sure...

3) Finally, I did what I should have done first, and developed a blank sheet. Straight out of the box into the tube, and developed. Same agitation method as #2. It looks like a fairly even gray, except for one end. This has a nice gradient down to a darker gray fuzzy line (about 1/4") wide running somewhat diagonally across the top the of sheet. My assumption is that this is a light leak from the tube, since it looks nothing like #1 or #2. Is this correct? It would form a circle if I curled the film up as it is when it's in the tube. Hard to see what else it could be.

If all this is correct, it looks like #1 is solved with better agitation, #2 is an in-camera error, and for #3 I need to add more duct tape to improve the light-tightness of my tubes (I already knew the PVC wasn't light-tight, but I thought I had enough duct tape!). Sound right?

 

[grahamp]

White or grey PVC, or black? The black ABS type that is standard in California is light-tight indoors. I still use my tubes ( http://grahampatterson.home.comcast.net/~grahampatterson/grahamp/darkroom/lfdevelop.html ) from time to time, but I put in enough solution to cover the film, and stand the tube upright. If you need semi-permanent light-proofing, you can try aluminium foil. The chemistry drips will attack it eventually, but that will give you a way to test light-tightness.

 

[tim k]

Take your stuff in a dark room with a flashlight, and look for light leaks.

 

[ic-racer]

Your unexposed sheet was gray? If you are using outdated or second-hand film from an opened box, the film could also have been spoiled from light before you got it.

Also, my personal opinion is that people have been developing sheet film long before PVC tubing was available, I'd just go with the tried-and-true method of, black-out material and some trays

To me this sounds like trying to construct some type of hovercraft mechanism to support the front of a wheelbarrow, when all you need is a wheel

 

[singerb]

It was very light gray, except for the area that I believe to be a light leak. I have a flashlight that fits inside the tube, so I put it in and turned it on, and indeed, it wasn't quite sealed. I believe I have now done so, and will try again this afternoon.

I would love nothing more than tray development, but I simply don't have the facilities to do so in my apartment; it has to be a daylight method. Now that I believe I've solved the agitation issue, and hopefully the light leaks, there should be no more problems.

 

[Ronald Moravec]

Film done in tubes needs constant agitation so the film rolls thru the developer on a regular basis.

For single sheets, it is easier to do a single sheet in a tray, emulsion up, lift and drop two adjacent sides every minute. The next minute do the other two sides. Lift as far as you can without spilling and drop. You want this to be vigorous.

Slip the sheet in one edge first rapidly immersing the whole sheet.

This method will produce perfect negatives.

do not let the timer glow hit the film at all. Nothing. Nada.