Eberhard effect - reference paper by nasa.

[el wacho]

hi everyone,


found this cool paper on the Eberhard effect. it has a great list of esoteric developers used in the tests and their formulae. the conclusion is interesting as it confirms alot of the anecdotal evidence regarding edge effects - high dilution, low or no pot. bromide and minimum/no agitation. enjoy!

 

[ath]

Thanks. Downloaded it for later reading.

 

[Alan Johnson]

A good explanation of the Eberhard effect in the blog Nov 22 2009 here:
www.photo-utopia.blogspot.com
It seems from the paper that in 1952 it was wanted to minimise it in astrophotography.

 

[el wacho]

thanks Alan,

from your experience Alan, would you say is it easier to generate edge effects from sod. hydroxide based developers as opposed to sod. carbonate based developers? i read somewhere that at high dilutions sod. hydroxide lacks the buffering power to replenish itself at the highlight/shadow border therefore more conducive to developer being leeched from the shadow side to the highlight side. if this is so, then a developer like fx-1 with the appropriate amount of sod. hydroxide would produce slightly more edge effects. what's your take on this?

 

[Alan Johnson]

My take is that the amount of edge effect varies with the film. Old emulsions like Adox/Efke 25, 50, 100, Plus-X, HP5+, Old Tri-X my tests showed to give the most effect.The least effect is with T-Max 100.
I found half-strength FX-1 produces the most edge effect, followed by dilute FX-2 then dilute Pyrocat-HD and Rodinal.
To produce the maximum edge effect with minimal streaking intermittent agitation can be used.I have found 10s every 5min to be satisfactory,IIRC this was suggested by D.F.Cardwell.
If carbonate in FX-1 is replaced by hydroxide,as you imply in theory the bromide produced by development should be more acidic.This should increase the fringe effect .However I believe the edge effect seen is not the fringe effect but the border effect due to diffusion of unused developer in the opposite direction.See "Controls in Black and White Photography" by R Henry p214.So using sodium hydroxide may not give any more visible edge effect.
But that is just theory,I have never made any measurements.

 

[el wacho]

thanks Alan,

when you refer to diluted pyrocat hd, what dilutions would you suggest? and i assume when you say half strength fx-1, you mean something like 1:1:20?

 

[df cardwell]

the maximum edge effect with minimal streaking intermittent agitation can be use....

I stole that from Crawley.

Adjust the rest times to your tank, film, and psychic condition of the moment. I think Sandy King goes 3 minutes with 120 in PyroCat. You can get freakishly shocking FX with TX in Rodinal 1+100, agitating only at the start and letting it sit for an hour, but you also get uneven development.

With FX-1, agitation can be reduced to fit the highlights to your paper, so you can precisely tune the density of your negs, AND the the FX at the same time.

BTW, can we take an oath to never repeat that confusing 'soot and chalk' mantra about FX1 that has followed it around for 50 years ? It makes a perfectly lovely, full scaled neg.

d

 

[Alan Johnson]

To produce the maximum edge effect I used FX-1 & FX-2 1:1:20 and Pyrocat HD 1:1:200..
Howevever this is tiresome as the development times are very long.
For practical use I found it more convenient to use FX-1 and FX-2 1:1:10
which gives times about 25min 70F agitating every 5 min for Adox 50 with negligible streaking.
I am sure others know much more about the use of Pyrocat than me so I will not give any data for that, I think it's here somewhere.

 

[ic-racer]

I stopped investigating these effects because I don't have a densitometer that will measure 0.6 mm from the edge of the image. I'm curious how others are testing for this.

 

[Alan Johnson]

My method was to photograph a light gray card on top of a black card using an old emulsion as in post 5 (I used Plus-X) ,stand develop without agitation 90min in FX-1or FX-2 1:1:20 or Pyrocat HD 1:1:200 or Rodinal 1:200.Then a 10x enlargement was made of the edge between the dark and light cards.The edge effect (border effect) showed up as a lighter line on the print about 1mm wide on the light gray card side.FX-1 always gave the greatest effect in my tests. I tested a lot of films as well,mainly in dilute Rodinal.There were a lot of streaks.
Scanning the edge also works after a fashion,I never pursued it.
www.apug.org/forums/forum37/51037-rodinal-minimal-agitation-stand-development.html

 

[Mike1234]

I stopped investigating these effects because I don't have a densitometer that will measure 0.6 mm from the edge of the image. I'm curious how others are testing for this.

With a good loupe.

 

[CBG]

Evidently you need a microdensitometer to measure density in very small areas. A little googling found this: www.astro.virginia.edu/~rjp0i/museum/PDSMicro.html . Don't think I'll be buying one for myself.