I see a number of independent threads debating agitation schemes, duration, and the merits - or lack thereof - of long, standing development.
I have a few observations that may- or may not be of use. These are based on many years of "normal" agitation and the past 3-4 years of fiddling with long, standing, dilute agitation. I still use both, but it was that latter "fiddling" that helped me understand film behavior a lot better. I hasten to add that these are my observations, not some inarguable font of truth and they are presented here in spirit of discussion, not theological debate ...
How Film Develops
What This Means
All things being equal this means that:
The shadows will continue to develop until you remove the film from development, or they have been in long enough to have developed to completion. More agitation does increase the effective EI somewhat (thereby giving you better shadow development), but mostly, increasing agitation will not speed up shadow development.
In summary:
What About Film Speed?
All things being equal, effective film speed (EI) :
All things being equal:
Strictly speaking, there isn't really such a thing as "pushing" film (mostly). What people call "pushing film speed" is really a combination of underexposing the shadows and overdeveloping the highlights to a much higher CI. You're really not increasing the actual effective EI all that much (though there are some developers that do this better than others).
So What?
Any time we talk about varying dilution, agitation, or time in developer, we're trading off between keeping the highlights in bounds, holding shadow detail, establishing and effective EI to make exposure calculations, setting our desired overall contrast and adjusting our mid-tone local contrast.
Manufacturer time/temp tables for agitation and try to split the difference between these: Leave the film in solution long enough to get "acceptable" shadow detail, but not so long that the regular agitation causes the highlight to overdevelop and blow out.
But you run into problems when you have a long Subject Brightness Range (SBR) - that is, a very big dynamic range of light, OR a very short SBR - that is, a very small dynamic range of light. The ordinary time/temp/agitation recommendations don't serve either case all that well. So going back over a century, monochrome photographers have been fiddling with time, developer formulae, dilution, and agitation to try to make negatives work well in SBRs outside "normal".
What About Zone System?
Zone System is one way to maniplate these variables:
So What's The Deal With Low Agitation?
Low agitation development schemes (semistand and EMA) are another way to optimize each of these independently. They work because by diluting the developer much more than usual, you can leave the film sitting there a lot longer. This has several consequences:
But There Are Issues
Low agitation is great when it works. But there are lots of ways for it to fail - LOTS of ways. When you do not agitate often, development byproducts don't get washed away and you can get really nasty streaks on your negatives (bromide drag). The "lots of ways" has to do with the many ways you can induce this - and believe me, I think I've found them all.
My observation - after a lot of experimentation - is that you have take care with two critical things when doing intermittent/low agitation:
Low agitation has some other gremlins. It's easy to overdo the increase in local contrast of the midtones and resulting image can have a harsh look to it. This has to be controlled with how long and how dilute you develop.
Also, since low agitation gives you sharp edges with Mackie Lines, it can be way too much of a good thing when you're shooting highligh textured surfaces. You can get a kind of graphic arts comic book look to things if you overdo it.
Finally, if you are using super dilute developers, everything gets sharpened including grain. So for smaller formats, like 35mm you have to find a dilution that supports long development but doesn't make the grain pop objectionably.
More Info
I keep ongoing notes of my work here:
gitbucket.tundraware.com
I have a few observations that may- or may not be of use. These are based on many years of "normal" agitation and the past 3-4 years of fiddling with long, standing, dilute agitation. I still use both, but it was that latter "fiddling" that helped me understand film behavior a lot better. I hasten to add that these are my observations, not some inarguable font of truth and they are presented here in spirit of discussion, not theological debate ...
How Film Develops
- Highlights develop to exhaustion very quickly
- Shadows develop very slowly
What This Means
All things being equal this means that:
- Highlight development is controlled by agitation
- Shadow development is (mostly) controlled by time
The shadows will continue to develop until you remove the film from development, or they have been in long enough to have developed to completion. More agitation does increase the effective EI somewhat (thereby giving you better shadow development), but mostly, increasing agitation will not speed up shadow development.
In summary:
- The more you agitate, the more the highlights develop (and you get a slight increase in film speed)
- The longer the film is left in the developer, the more completely the shadows will develop
What About Film Speed?
All things being equal, effective film speed (EI) :
- Increases if you leave the film in developer longer or use less dilute developer
- Decreases if you leave the film in developer for less time or use more dilute developer
All things being equal:
- Longer development increases contrast (CI)
- Shorter development decreases contrast (CI)
- Longer development times increase the local- or "micro" contrast of the mid-tones
- Shorter development times decrease the local- or "micro" contrast of the mid-tones
Strictly speaking, there isn't really such a thing as "pushing" film (mostly). What people call "pushing film speed" is really a combination of underexposing the shadows and overdeveloping the highlights to a much higher CI. You're really not increasing the actual effective EI all that much (though there are some developers that do this better than others).
So What?
Any time we talk about varying dilution, agitation, or time in developer, we're trading off between keeping the highlights in bounds, holding shadow detail, establishing and effective EI to make exposure calculations, setting our desired overall contrast and adjusting our mid-tone local contrast.
Manufacturer time/temp tables for agitation and try to split the difference between these: Leave the film in solution long enough to get "acceptable" shadow detail, but not so long that the regular agitation causes the highlight to overdevelop and blow out.
But you run into problems when you have a long Subject Brightness Range (SBR) - that is, a very big dynamic range of light, OR a very short SBR - that is, a very small dynamic range of light. The ordinary time/temp/agitation recommendations don't serve either case all that well. So going back over a century, monochrome photographers have been fiddling with time, developer formulae, dilution, and agitation to try to make negatives work well in SBRs outside "normal".
What About Zone System?
Zone System is one way to maniplate these variables:
- For very high contrast (long SBRs), we can reduce development time, but at a cost of reducing effective EI
- For low contrast (short SBRs), we can increase development time, also getting a somewhat higher effective EI.
So What's The Deal With Low Agitation?
Low agitation development schemes (semistand and EMA) are another way to optimize each of these independently. They work because by diluting the developer much more than usual, you can leave the film sitting there a lot longer. This has several consequences:
- Leaving the film in highly dilute developer for a long lets the shadows fully develop - effectively giving you box EI speed
- Leaving the film in highly dilute developer for a long time expands the local or microcontrast of the middle tones
- Agitating a lot at the beginning and then very littler thereafter keeps the highlights from overdeveloping or "blowing out"
- For some schemes and developers you get "Mackie Lines" along the light and dark boundaries which the eye perceives as improved sharpness
- Many developers produce noticeably sharper negatives when the developer is highly diluted
But There Are Issues
Low agitation is great when it works. But there are lots of ways for it to fail - LOTS of ways. When you do not agitate often, development byproducts don't get washed away and you can get really nasty streaks on your negatives (bromide drag). The "lots of ways" has to do with the many ways you can induce this - and believe me, I think I've found them all.
My observation - after a lot of experimentation - is that you have take care with two critical things when doing intermittent/low agitation:
- Get the film off the bottom of the tank. It seems that doing this allows gravity to pull away the development byproducts from the film to settle at the bottom. For this reason, I suspend sheet film horizontally in a large tank, and I place reels on an inverted funnel in a double height daylight tank.
- Use minimal contact support systems for the film. The more stuff that holds the film, the more opportunities there are for developer to get trapped and slowly bleed development byproducts onto the film surface. For sheet film, I use a Kodak #6 hanger which has tiny clips on it. Every other scheme I have tried including the usual sheet film frame holders, sooner or later shows bromide drag. The Yankee sheet film tank is equally awful in this regard. For rollfilm, I only use Nikor style stainless reels and tanks. Reel systems with high walls along the wind surfaces of the reels (like most plastic reels) will trap developer and inflict bromide drag sooner or later.
Low agitation has some other gremlins. It's easy to overdo the increase in local contrast of the midtones and resulting image can have a harsh look to it. This has to be controlled with how long and how dilute you develop.
Also, since low agitation gives you sharp edges with Mackie Lines, it can be way too much of a good thing when you're shooting highligh textured surfaces. You can get a kind of graphic arts comic book look to things if you overdo it.
Finally, if you are using super dilute developers, everything gets sharpened including grain. So for smaller formats, like 35mm you have to find a dilution that supports long development but doesn't make the grain pop objectionably.
More Info
I keep ongoing notes of my work here:
tundra/Stand-Development
gitbucket.tundraware.com
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