Efke films, exposure latitude, and overexposure

karthik · Oct 13, 2010

Hi all,

Could someone explain how to reconcile the following:

(a) From http://www.freestylephoto.biz/efke.php

Efke films are manufactured using classic emulsions with very high silver content. This results in a large exposure latitude and superior grayscale reproduction ... Unlike modern flat crystal films, which are very unforgiving to use, these films allow beginners to produce quality images.

(b) From http://www.freestylephoto.biz/1911100-Fotokemika-Efke-KB100-iso-100-35mm-x-100-ft.?cat_id=402

Do NOT over-expose Efke Emulsions!

(c) From p.665 of "The Focal Encyclopedia of Photography" (can be viewed on Google Books), section on "Film Exposure":

Strictly speaking, film only has latitude toward overexposure keeping shadow exposure constant. Ignoring a slight increase in grain size, there is no loss of visible image quality with overexposure ... Film has no latitude towards underexposure, because film speed is defined as the minimum exposure required to create adequate shadow density. Practically speaking, however, film has some underexposure latitude, if we are willing to sacrifice image quality.

From (a) I would have guessed that Efke films are more tolerant of over/underexposure than, for instance, T-Max (and perhaps no more tolerant than Plus-X since that is not a tubular grain film). But (b) advises not to overexpose Efke films. Finally (c) says that exposure latitude is meaningful mostly in the context of how much overexposure the film will allow and still be printable.

So what exactly is meant by the statement that Efke has greater exposure latitude?

Thanks --- Karthik

clayne · Oct 13, 2010

Marketing. Just pull it any which way you want and don't worry about it.

Ian Grant · Oct 13, 2010

EFKE films are very sharp and fine grained, over exposure kills that sharpness, and you lose some tonality.

Treat a B&W film as you would a colour transparency film when it comes to exposure accuracy and you'll get consistently high quality results, that's not at all difficult and it takes no longer What it means though is you'll have negatives that are far easy to print, and more open to interpretation at the printing stage.

Ian

Leigh Youdale · Oct 13, 2010

Since the Efke brand has come up again, I have to report that I've been trying out the various types (100, 50, 25) in 35mm and 120. I've come up against the dreaded "black spot" emulsion quality problem that's been widely reported in the past. It's patchy and doesn't affect every frame on the films but always some are affected and some are downright terrible - unprintable, in fact. Some of my shots when scanned look like a light snow storm (well, a little exaggeration). The tonality was wonderful but the spotting just killed any interest I had in further tests.
I tried Foma a while back and had problems with their quality control too. Threw out a bunch of unexposed film. I'm about to donate 13 Efke films to the local school for the Holga fanatics there to play with as I can't live with the problem any longer. It's Fuji Acros, Kodak or Ilford and nothing else for me from now on.

polyglot · Oct 13, 2010

It depends which emulsion you're talking about. I've found KB-25 to perform relatively poorly with overexposure (a bit like Pan-F) while IR820 just has a decrease in contrast and increase in grain size. In one case, I exposed IR820 without the R72 filter at EI1 (which is about 6.6 stops too much) yet there was a printable, if quite dull and grainy, image there. The neg was seriously thick and most of the sharpness & contrast had been destroyed by halation, to the point where there was visible density extending about 3mm outside the mask.

2F/2F · Oct 13, 2010

As Ian mentioned, the older formula emulsions get very grainy and mushy, and tonal relationships can look a bit strange, upon overexposure with normal development. IME, if you adjust development when you underexpose, these films are less affected.

Newer films are less technically demanding in almost every way than these Efke emulsions. You need to be more dead on with exposure and more careful with processing and handling the Efke films. However, the Efke films are worth the extra work and extra care sometimes, as they can make very beautiful and unique images.

RobertV · Oct 13, 2010

EFKE films are very sharp and fine grained, over exposure kills that sharpness, and you lose some tonality.

Exactly.

I am only using the iso 25 variant. It has Orthopan characteristics too. Use this film on iso 25 or 50 for the best results.

Above mentioned description(s) is/are comming from the Fotokemika website:
http://www.fotokemika.hr/

Ian Grant · Oct 13, 2010

EFKE have been saying the same for many years, here's the 1974 datasheet I saved

It seems it's 36 years since I began using KB14 - the old DIN name, it's now called by it's ISO speed KB25. I've used it in all formats from 35mm (KB25) to 10x8 (PL25) because I really like it's fine grain & sharpness. It's great in staining developers like Pyrocat.

I've always used the 25 ISO film at 50EI, the films speed is based on it's sensitivity in Tungsten light not daylight. In the UK KB25 was sold re-badged as Jessops films as a 50 EI emulsion.

Ian

c6h6o3 · Oct 13, 2010

karthik said:
From (a) I would have guessed that Efke films are more tolerant of over/underexposure than, for instance, T-Max

Not my experience at all. TMax is more sensitive to development than non tabular grain films, but not to exposure. I rate my 400TMax at 100. My negatives are very sharp with very little grain.

Dave in Kansas · Oct 13, 2010

polyglot said:
I've found KB-25 to perform relatively poorly with overexposure (a bit like Pan-F) while IR820 just has a decrease in contrast and increase in grain size.

Maybe I've taken this out of context, but I've found Pan-F to be a most beautiful film over exposed by one stop (EI 25). I also reduce development, but the results are beautiful.

Dave

c6h6o3 · Oct 13, 2010

Over development increases grain and reduces sharpness. Over exposure does neither. I think this is true with any film. And I agree about Pan-F. How I would love to see that emulsion in a sheet film.

ic-racer · Oct 13, 2010

Modern "flat crystal" films are the most forgiving to use. Good for beginners and good for experts. Too bad the best one is made by a company that does not seem interested in film.

MattKing · Oct 13, 2010

Ian Grant said:
EFKE have been saying the same for many years, here's the 1974 datasheet I saved
.......

Ian

I've figured out why Ian prefers a water rinse over stop bath - he has most likely run out of room!

RobertV · Oct 13, 2010

I've figured out why Ian prefers a water rinse over stop bath -

I would expect the opposite: Ran out of water (Turkey)

Can you develop films also in goat's milk? or is Turkish coffee the better one......

Ian Grant · Oct 14, 2010

No way would I run out of water, the sea's only 2 minutes walk That's fine for a rinse and most of the washing

I only drink Turkish tea, my wife told me I'd dislike it as it's too strong but in fact it's not a all . . . . .

Actually with EFKE films in the 70's I used a hardening stop-bath which used chrome alum, that stopped the emulsion sliding off the film base, but in more recent years there's some hardening done during manufacture. If you use a tanning developer like Pyrocat that helps as well.

Ian

karthik · Oct 14, 2010

Thanks everyone for the comments!

Ian: When you said "overexposure kills that sharpness", did you mean just the highlight values getting blocked? I wasn't sure sure why low values will show deterioration on overexposure. (I assumed the same as c6h603 re. overdevelopment and overexposure).

c6h6o3 & ic-racer: I presume the blurb about Efke being better for beginners is more marketing fluff than anything.

Ian Grant · Oct 14, 2010

No you actually lose sharpness because the over exposure negates edge effects and micro contrast across the whole dynamic range

Ian

c6h6o3 · Oct 14, 2010

Ian Grant said:
No you actually lose sharpness because the over exposure negates edge effects and micro contrast across the whole dynamic range

Ian

I don't do much enlarging. Any discussion of grain or sharpness becomes pretty much moot when you're making contact prints. And when I enlarge, I never go beyond 8"x8" full frame prints from my 6x6cm negatives.

So I'm not going to see any loss of sharpness due to overexposure, and I see very little due to overdevelopment.

Ian Grant · Oct 15, 2010

Well I use EFKE/Adox 25 in 10x8 and I can assure you over exposure and loss of edge effects will be noticeable even with contact prints, over development is slightly ess of an issue.

Ian

Athiril · Oct 15, 2010

There's little overexposure latitude, unlike with many other negative films is what it means.

You can overexpose it 4 stops or x stops and pull developing to match just like with any other film though.

I've shot Pan F+ @ EI 12, Rodinal development

2F/2F · Oct 15, 2010

To overexpose is advice I often give to those looking for a lot of grain. Even with modern-style emulsions, heavy overexposure (2+ stops; the more the "better") will increase graininess in an obvious way. This effect is even more severe with the Efke/Adox emulsions. This being said, the effects are also related to development. Overexposure and normal development, or overexposure and overdevelopment, give a lot of density, which is tied to graininess. Reducing development makes for less density, thus less graininess.

Usagi · Oct 15, 2010

Interesting discussion so far.

I would like to ask that how do you define over exposure? For example, I got exposure index 50 for EFKE/Adox CHS 100 under daylight tests using Pyrocat-HD 1:1:100. That's almost two stops more than the old datasheet specifies.
Still get really nice tonality (classic 0 - X scale) which keep me using this film with all the problems it does have with poor quality control.

Ian Grant · Oct 15, 2010

That's the same EI as I use for EFKE/Adox PL25 with Pyrocat HD 1:1:100

However I've heard similar before. I think I've finished my EFKE stocks and what I'd thought was three more boxes of 10x8 turns out to be Classic Pan (Fortepan) 200, the labels were so small and barely legible.

When talking about over-exposure we mean the resulting processed negative, it's tonality and overall densities, rather than the difference between the Manufacturers ISO rating and the effective EI we find by testing.

Ian

Usagi · Oct 15, 2010

Thanks for the definition

I don't know how Efke/Adox CHS 100 would behavier if I would try to print out of tones from densities above 1.4-1.5 (from dmin). Probably grainy and very low in contrast.

Efke films, exposure latitude, and overexposure

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