Measuring film resolution

[Rudeofus]

Ilford Delta speed seems to cause huge confusion. It's very simple. Ilford use ID11 for all their ISO speed tests. Using ID11 my tests indicate that yes indeed its ISO speed is 1000. But EI is your own personal speed and is dependant on the devloper used and your own process. I find I get 1600 with DDX and I get 3200 with Microphen. Grain is much bigger with Microphen than with DDX so DDX produces much smooither looking prints than Microphen but certainly not what I would call fine grain.

It is quite unlikely that anyone can come up with any developer that would develop Delta 3200 to real ISO 3200, not because people aren't smart, but rather because the inventors of DD-X and TMAX weren't dumb either. If ID-11/D-76 gives you ISO 1000, it is possible for an optimized developer to give you ISO 1200, 1300, maybe 1600 with this film, but not twice that.

I may be wrong but my impression is that the closer to neutral PH a developer is, the finer the grain. Its important to remember that the grain we talk about is actually grain clumps and its my belief that the further away from neutral PH(7) a developer is, the greater the grain clumping. The increased hydrogen ionisation cause greater attraction of real grains to each other forming bigger grain clumps. The developer is "more active".

It's the activity of the developer, not its absolute pH which to some extent determines film grain. Remember that Amidol operates in acidic environment, but nobody ever praised Amidol for its fine grain properties, while people happily used PPD which lost them two to three stops.

Grain is a difficult animal, and there is no single or easy to follow strategy of the "the more you do this the better it gets" kind how to improve granularity.

 

[RobC]

It is quite unlikely that anyone can come up with any developer that would develop Delta 3200 to real ISO 3200, not because people aren't smart, but rather because the inventors of DD-X and TMAX weren't dumb either. If ID-11/D-76 gives you ISO 1000, it is possible for an optimized developer to give you ISO 1200, 1300, maybe 1600 with this film, but not twice that.

It's important to remeber that "ISO" is just a common standard used for comparitive reference and not some scientific law. EI on the other hand means it can be whatever you can achieve and an EI of 3200 is perfectly achievable with Delta 3200 and Microphen. Whether you like the granularity of it at 3200 is another matter.

 

[Rudeofus]

Rob & Athiril: you can expose any film at EI 3200, as I wrote before. It depends on film, developer and processing, though, how much light is needed to get usable density. Perceptol will give you finer grained Delta 3200 negs than Microphen, but Microphen will create density in low exposure regions where Perceptol won't.

 

[RobC]

Microphen will create density in low exposure regions where Perceptol won't.

Agreed. Infact around 800 is all you'll get with Perceptol and Delta 3200 which I did test.

 

[Rudeofus]

The key term is detective quantum efficiency. You can gain some resolution if you give up ISO speed in return and vice versa. If you knock Delta 3200 down to ISO 400 with some ultra fine grain developer, you may still be worse off than with TMAX 400 and D-76.

 

[Photo Engineer]

Most people confuse a contrast increase with a speed gain!

PE

 

[RobC]

Most people confuse a contrast increase with a speed gain!

PE

but delta 3200 is actually a low contrast film which when developed in a push developer such as Microphen, it produces a normal contrast negative.

So those that don't know what they're starting with can confuse themselves.

 

[Ronald Moravec]

I would do a practical test because that is all that matters. Tripod or at least flash. Slowest film you can afford to use, D76 1:1, then look at the resulting negs through your grain magnifier , 8 x plus 10x Peak magnifier = 80x.

If a film resolves 400, but your lens only 150, all you will ever get is 125 guesstimate. Now the enlarging lens and paper each knock it down some more. You will be lucky to end up with 68-80.

More can be done with microfilm and the special developers, but pictures are not pretty.

 

[Photo Engineer]

In my experience, some of the finest grain I have seen was achieved with very high pH developers.

PE

 

[Alan Johnson]

In my experience, some of the finest grain I have seen was achieved with very high pH developers.

PE

Are you referring to developers containing thiocyanate?
http://www.digitaltruth.com/products/msds/SPUR_HRX3_MSDS.pdf

 

[Photo Engineer]

Alan, the English used in that MSDS was worth a morning read. It was unusual to say the least.

However, the answer is NO.

PE

 

[Rudeofus]

Ron, allow me to rephrase Alan's question: was that ultra fine grain due to added solvent, was it due to choice of development agent, or due to other factors?

 

[Photo Engineer]

Other factors I would have to say.

 

[falotico]

In my experience, some of the finest grain I have seen was achieved with very high pH developers.

PE

Isn't it correct to say that reducing agents like developers are more efficient in high ph--alkaline--solutions? This greater efficiency might cause some of the smaller silver halide grains to be reduced, while they might not be in more acidic solutions.

 

[Photo Engineer]

I could not say on that, but it seems that larger grains are often harder to develop.

PE

 

[Rudeofus]

Other factors I would have to say.

Sounds like you refer to diffusion transfer systems which are 100% physical development and use lye as accelerator.

 

[Photo Engineer]

That is one but uses a solvent. I said above, no solvent.

PE

 

[Alan Johnson]

Some kind of staining/tanning developer?
Dead Link Removed

 

[Photo Engineer]

No, and I don't wish to discuss it any more!

Sorry.

PE

 

[Rudeofus]

Since you won't allow me to ask whether you by any chance meant heat transfer film, I would like to dig up some older topic in this thread, which is resolution vs. exposure. From my very limited experiments I sort of knew that excessive exposure causes blooming effects, but now I finally got around to reading Marilyn Levy's famous POTA article (Photographic Science and Engineering, vol. 11, pp. 46), and sure enough, Levy claims a strong relationship between exposure and contrast.

Attached to this posting are three graphs which compare exposure vs. resolution for POTA and D-19, the latter one a high contrast MQ developer, not too much different from D-76 and the like. With increasing exposure resolution builds up at first, only to go down again as film goes into saturation.

Graph labelled "Levy Resolving Power vs. Exposure.png" depicts the resolution of Kodak RAR 2494 recording film exposed with variable light intensity.
Graph labelled "Levy Resolution vs. 1_1000 Exposure.png" shows two film areas contact printed through USAF 1951 resolution target at normal exposure and at 1000 times normal exposure.
Graph labelled "Levy Resolution vs. Exposure High Contrast Target.png" shows the resolution of Kodak Microfile film exposed with variable light intensity. Different film from first graph yields very similar results.

 

[Photo Engineer]

I had the opportunity to meet her. I believe it was just before she retired. I also seem to remember Grant Haist introducing us, but I may be wrong on that. We talked about - developers, what else.



PE

 

[Photo Engineer]

Levy was about to retire when I first started in this game!

But yeah, I know or have met most of the scientists reference here and also many of the photographers from a bygone era. Seems like when you are just getting good at this, you are getting old.

PE

 

[Alan Johnson]

Regarding the choice of developer for resolution testing,Sandy King investigated this and found some difference:
(there was a url link here which no longer exists)

 

[Rudeofus]

Alan, I am not after the sharpest developer. A good general purpose developer, as far as I am concerned, is a developer which gives good overall results and which can be easily modified to tilt its balance in one specific direction (speed, sharpness, grain).

If you look at Xtol, people do this "tilting the balance" by changing dilution from stock (fine grain) to higher dilutions (speed & sharpness). Add some lye and you'd probably gain a tiny bit of extra speed at the expense of grain and fog.

My first film tests were done with real image matter, and they were inconclusive at best, and sometimes outright misleading. This is why I ordered that Lasersoft resolution target now, hopefully I will get more meaningful feedback whether certain modifications have an effect and to which extent.

 

[Photo Engineer]

I would add though that many commercial brands of Lye here in the US are crap. Some have obvious contaminants in them in the form of black or brown crystals, but the stuff is often not very good.

PE