Re: Sprocket Shadows

[mturner@xxxxxxxxxxxxxxx (Marc Turner)]

     >I have noticed rather pronounced light-dark patterns across the top 
     >of some of my images that match the sprocket holes in the HIE.  I 
     >don't believe I have seen this when I expose in my usual camera 
     >(Nikon 8008s).  It shows up in the panoramic format.  I use the 135 
     >panoramic adapter in a Mamiya 6MF range finder.  The pattern shows 
     >that the sprocket hole seem to cast a shadow into the image area .
     >(goes in about 10% of frame height or less). It's as though light is 
     >leaking in along the whole edge of the film, but is blocked by the 
     >holes before getting to the image area.  Strangely, I see no evidence 
     >of exposure beyond the image area.  Perhaps there is not enough light 
     >to overcome base plus fog in unexposed regions, but it's noticeable 
     >where exposure has already occurred (like pre-flashing).  Any ideas 
     >about what's causing this and how to stop it.  It is ruining those 
     >images that have the relatively clear zone III skies across the top.
     >Thanks,
     >EltonK
     
     
     
     Someone on another list, I believe it was PhotoForum or possibly on 
     the Jobo site, was having a similar problem with streaks around 
     sprocket holes.  I don't recall who provided the following response, 
     but I made a copy for my own possible future reference.  Here is what 
     they said:
     -- Marc
     
     "Most streaks I've seen result from agitation problems. Essentially 
     what happens is that active developer swirls through the 
     holes--sprocket holes in 35mm or the drain holes in large format film 
     hangers. The swirling developer agitates more than the relatively 
     still developer in other areas. The streaks are overdeveloped areas of 
     film. Eliminating the holes won't work. I want to keep using metal 
     hangers, and I can't think of a way to eliminate the sprocket holes 
     from 35 mm! Hmm.. An advantage of 120? 
     A Solution - The approach I've taken to eliminate streaks is based on 
     advice I got from Ilford's tech support department. They said that 
     most streaking was caused during early development (first couple of 
     minutes). So limiting agitation during the critical first minute 
     reduces streaks, and has little affect on total development or 
     contrast. Here's my current strategy: 
     Use developer/ dilution/ temperature combinations that keep 
     development times long. (8 minutes or longer is my rule.) 
     Pre-wet the film--even 35mm. 
     Be gentle getting the film into the developer. (Don't use a "slam 
     dunk" to get the film into the developer fast. No quick immersion of 
     the 35mm development reel--no dropping the film holders into the 
     tank.) 
     Agitate once right away (gently) to get any bubbles off the film (I 
     just bang the tank on the table to knock any bubbles loose). 
     Don't agitate at all during the first minute, and only lightly agitate 
     during the first two minutes. (This is the important part; one tank 
     inversion.) 
     Use normal agitation for the rest of the development so contrast is 
     consistent. For me normal agitation is 4 tank inversions. 
     With sheet film in holders, keep the film holders separated a little 
     so that developer won't be forced in and out through the bottom holes. 
     These changes to my development routine have largely eliminated 
     streaks."
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