The Effect of Different Methods of Agitation

Aside from some developers that provide some unique charactoristics like edge effects of Rodinal, or stand developing, agitation has to do only a few things.

Provide fast even wetting of the film initially. The wet /dry edge has to start and move across evenly and rapidly with no stop/start or retreat.

Provide enough flow of developer to remove developer by products so there is no streaking.

Use a technique so the whole of the film surface is refreshed. If you have so called "surege marks", the scheme you are using is not vigorous enough or you are settiing up a pattern so some portions of the film are not refreshed.

Agitation is best NOT used for contrast control although it has some influence. That is what your clock is for.

If you think it does more than this, you are not following good science. Pick something that works, and it will work with all common developers.
 
One more factor to consider is the intensity of the agitation. By pausing for a couple of seconds between tank inversions, and doing fewer of them every minute I seem to have cured streaking problems in 120 films - Agfa, Kodak and Ilford. Easy does it is the byword in my darkroom these days
Murray: glad to hear you're having fun with the Technidol.
Cheers:
Morry Katz Lethbridge AB
 
bmattock said:
Very general, because this is not true for all developers. However, in very general terms...

1) More dilution may increase accutance up to a point.

2) Longer development time means less deviation by percentage is likely.
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Thus it would seem (and please don't flame me for generalisation) that higher dilution gains somewhat more desirable results? Meaning using higher dilution where poissible should be prefered?
 
A great many people believe exactly that. The only contentious issue is what one defines as 'desirable'. Myself, I like the tenet. It is faith, after all.

Murray
Phantomas said:
Thus it would seem (and please don't flame me for generalisation) that higher dilution gains somewhat more desirable results? Meaning using higher dilution where poissible should be prefered?
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Richard Jenkinson said:
No friends or women that I know.

Does that diagram really mean anything, do you understand it?
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Dear Richard,

The D/log E curve (also known as an H&D curve because these curves were devised by Hurter and Driffield in 1890) is a graphical representation of a film's response.

Of course you don't need to know anything about it. That's why they make point-and-shoots. For that matter, there are plenty of excellent photographers whose knowledge is entirely empirical. Surprisingly many of them harbour fundamental misconceptions about how and why things work, it's true, but that rarely matters until they try something unfamiliar.

But once you want to advance your understanding of the photographic process beyond a certain point, you need to understand D/log E curves -- just as it's a good idea to read poetry in the original language, if you're not happy about relying on others' summaries and translations.

Comparing different D/log E curves for different films can also tell you quite a lot about the difference between them.

As for friends and women, well, quite a lot of my friends and a number of women I know (including my wife) take the understanding of D/log E curves for granted. And they (and I) had to learn somewhere. Impress people? No. Communicate with them? Yes.

Cheers,

Roger
 
Phantomas said:
Thus it would seem (and please don't flame me for generalisation) that higher dilution gains somewhat more desirable results? Meaning using higher dilution where poissible should be prefered?
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If higher acutance is what you want. That is not always the case.

Take D-76. Used in a stock solution, it produces a finer grain, but lower acutance. Used diluted 1+1, it produces a rougher grain, but higher acutance. Acutance is a funny thing - it is 'apparent' sharpness, done by making edges sharper. Sometimes finer grain, lower apparent contrast, and lower acutance are desirable.

http://en.wikipedia.org/wiki/Sharpness_(visual)#Sharpness

Coarse grain or noise can, like sharpening filters, increase acutance, hence increasing the perception of sharpness, even though they degrade the signal-to-noise ratio.
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I tend to prefer a longer processing time over a shorter time. Therefore, I will tend to use higher dilutions of developers to arrive at around a 10 minute dev time - I could also manipulate temperature (colder water) to get the same dev time, but I find it easier to calculate developer dilution. I do tend to prefer acutance over smooth grain, but not everyone does. So the choice is yours.
 
bmattock said:
I don't want to speak for others, but in my own opinion, home development of B&W film is like being an audiophile, or a supreme-lens hunter, or etc. That is, there is a point of diminishing returns. I do what I enjoy and skip the rest. This horrifies the religiously-inclined damaged minds, which is fine with me. I'm a happy little heretic.
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Agree with the point of diminishing returns. I also do DIY film development for the fun of it.

I don't want to make it a scientific crusade, nor do I want it to take away my time for more important things in life.

As for audio-philia, I still use the simple stereo system I bought out of college 15 years ago 😛
 
There are three ways ways of answering any question about technical photographic points.

Broad and useful generalizations (thanks Bill), vague impressions, and a bit of hard science.

All right, four. Smart-arse non-answers, mercifully few on this thread.

You can never tell what the OP was looking for.

He's got lots of the first three by now, and some of the fourth too.

As for the 'snobby intellectual class', they're more common among arts graduates than science graduates. The latter know that their assertions can be tested. Although as a law graduate I cannot claim either approach as of right, I try whenever possible to supply testable assertions. Which is, I suppose, part of law. But as Cicero said (sorry, I can't remember it in Latin), "When the law is against you, plead justice. When justice is against you, plead the law."

Tashi delek,

R.
 
Roger Hicks said:
There are three ways ways of answering any question about technical photographic points.

Broad and useful generalizations (thanks Bill), vague impressions, and a bit of hard science.

All right, four. Smart-arse non-answers, mercifully few on this thread.

R.
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Yes, thanks again to everyone for their replies.

I of course understood that my question would be open to the points stated above, though I expected more of the latter than has occured. So thanks again.

The standard "Get over yourself, take some pictures and get off of the internet" dummy-type post is the certainly the most dreaded.

"Ummm sorry, don't you have anything better to do?"

Anyway it just seemed that in most books there was usually only a fast paragraph on the subject of agitation. I thought it likely that any difference would probably only be minimal, though I wanted to know what that difference might be.

I have looked at the Hurter and Driffield diagram before, and they are less dull than lens testing charts. The book I learnt the most from, technically at least, was Perfect Negatives by Glover and Wakefield and they made common reference to their work.

I'm glad somebody brought it up as it is most certainly relevant to my question; if not in the text then at least in my reason for having asked.

Anywar thanks again,

Benjamin
 
I'd like to know what "toe speed" is, in plain english. The diagram looks like the curve adjustment in photoshop. It seems to have something to do with shadow detail, am I right?
 
Melvin said:
I'd like to know what "toe speed" is, in plain english. The diagram looks like the curve adjustment in photoshop. It seems to have something to do with shadow detail, am I right?
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Initially, the first tiny exposure has no effect at all. This is 'inertia'. Pre-flashing is sometimes used to overcome inertia.

Then, at first, the relationship of density (D) to the logarithm of the exposure (log E) is not linear. You need quite a lot of light to make a small increase in density. This is the 'toe'.

Slowly the toe gets steeper until it hits a more-or-less constant slope: the 'straight line portion'.

Eventually, there's not much more density available to add, and the slope starts to flatten out: you need more and more light to achieve a given density increase. This is the 'shoulder' because the curve 'shoulders off'.

Finally, with enormous overexposure, density may actually decrease. This is the region of true soplarization, so called because it was first seen when the sun recorded as a clear dot on the negative, instead of maximum black.

You can change the shape and slope of the curve to varying degrees via developer choice, time, temperature and agitation.

In anything resembling a normal exposure, you use the toe and the lower end of the straight-line portion. Only rarely, or with special development techniques, are you likely to get onto the shoulder.

Speed is measured at a point on the toe where you get a 'useful' density, i.e. adequate shadow detail. Today this is defined as the amount of light required to give a density of 0.10 above film base plus fog. This is a good, easy number but there are plenty of theoretical grounds for suggesting other criteria.

Whole books have been written on exposure theory, including my own Perfect Exposure, but the above should help you understand the basics. Take a look at the ISO speed module on my site for more detail:

http://www.rogerandfrances.com/photoschool/ps iso speeds.html

and the density and D/log E module:

http://www.rogerandfrances.com/photoschool/ps neg density.html

Tashi delek,

Roger
 
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Does it matter?

Does it matter?

I think Bill Murray said it best in "Meatballs",

"It just doesn't matter."

Observe the two attached photos. I'll give you a few particulars:
Same camera and lens for each.
Ilford HP5+ for 1 and Pan F+ for the other.
Agitation as different as night and day.
Can you tell the difference? Can you spot the difference?

Gruene+Oct+2008+_1+of+5_.jpg


Gruene+Oct+2008+_5+of+5_.jpg


One more difference: 2 developers.
 
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The amount of Agitation plays a large part in the control of highlight densities to control the contrast range.
Dilution the way i understand it controls the amount of time it takes to arrive at the contrast range you are looking for.
In my own film tests i found i was getting more film speed the longer the film was in the developer combined with minimal agitation .
Thanks
 
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