Question about film density (what is it, etc)

[telenous]

So, what is it? I find lots of people talking about it in the Darkroom forum, and they talk of it as if controlling the density of b&w film gives you better scanning, printing etc. (there's also some jargon about 'thick' and 'thin' negatives - is that the same thing as 'dense'/'non-dense')?

I 've googled it but after reading a couple of pages I am none the wiser. It seems that there is something called 'optical density', a property inherent in the film stock. Here's a quote

The optical density dynamic range of film describes the optical density of the film itself between its lightest and darkest parts, and is measured by how much light is transmitted through the film with standardized densitometric equipment. It is expressed in log units.

I assume the same goes for B&W. But what is the optimal density one should aspire when in the darkroom and with scanning in mind? And how do you influence it in development?

Thanks for any answers in advance,

 

[Nachkebia]

Whaat? 😱 😱 what are you talking about? 😀 I was also interested what thin and thick mean 😀

 

[telenous]

Whaat? 😱 😱 what are you talking about? 😀 I was also interested what thin and thick mean 😀

I don't know what I am talking about - that's the problem 😀 :bang:

It's just that some people here emphasize the 'thickness' or 'thinness' (I am not even sure I use the right words) as influencing the scanning or printing result.

Help? 🙂

 

[Pherdinand]

the optical density (o.d.) in log units is a general parameter in optics to express the light transmitting (absorbing) properties of any material. The text you quote refers to this density in general, for a piece of film that is completely blocked up versus another piece that is completely clear (a totally overexposed versus a totally unexposed film).
What I understand when people talk about dense or thick negatives is, it's about an exposed frame that has both highlights (dense regions, not very transparent) and shadows. When you look at a frame like this, or sometimes at a number of frames on a roll of film, you can see a general tendency if it is "normal", aka correctly exposed and developed, or "thick" (too much of dense regions, that is, overexposed or overdeveloped) or "thin", the opposite. For scanning, in general the thinner negative is preferred.
Is this of any help?

 

[Nachkebia]

:bang: :bang: :bang:
After developing some films I have noticed some are thin some are thick but I can not control it 😀 anyone can? well except god of science 😀

 

[Pherdinand]

Well, I have only experience with scanning, but a thin (slightly underexposed) negative is easier to scan than a thick one, or even a normal one.

 

[Trius]

It's basically exposure and development. You need a minimal exposure to get adequate shadow detail, and then the "correct" amount of development to get tonal gradation without the highlights being blocked up.

In B&W, that means that Zone I blacks should have minimal detail, i.e., they should print with some information as opposed to the total black of unexposed but developed film. (The latter is film base plus chemical "fog".) The highlights should print through with Zone VIII having tonal separation; Zone VIII is (was?) considered the highlight tonal range limit of traditional b&w paper's (for grade 2 "Normal" paper) ability to render detail in whites.

Exposure determines shadow detail, development determines highlight detail placement. That's a generalization, but is a good guide.

Colour film development is pretty well set at standard time and temperature. You can manage some manipulation through developing times, etc., but then you may also get colour shifts, which of course aren't a factor with b&w.

I'm sure others will add to my "vintage" understanding. The claim is that slightly thinner negatives (mostly through slightly reduced development) makes for better scanning because the dynamic range of most scanners is less than b&w negatives can carry with "standard" development.

Edit: Using underexposure to control density can result in inadequate shadow detail. Development is the better tool unless we are talking about colour or C41 b&w films. JMHO.

 

[markinlondon]

Density in this context refers to exposure, Alkis. A "dense" or "thick" negative is one that has been generously (over?) exposed. A "thin" negative would be underexposed and/or underdeveloped. "Thick" negatives will often be difficult to scan or print as detail will be lost in just passing light through the emulsion. "Thin" negs tend to scan well but need higher paper grades or filters to print with shadow detail.

 

[telenous]

Just to say a very, very quick 'thanks a bunch' to all of you and I am scrolling back to re-read the replies 🙂

 

[Nachkebia]

Well, I have only experience with scanning, but a thin (slightly underexposed) negative is easier to scan than a thick one, or even a normal one.

Eeeexactly! thats why I underexpose almost all the time (black and white) but after using vuescan (Raw) files I don`t need to 🙂

 

[markinlondon]

Underexposure would run the risk of "empty" shadows. Better to produce a flatter negative by slight underdevelopment as this helps keep the contrast within the scanner's dynamic range. This is also true for those working with condenser enlargers. When I scanned film Vuescan was indispensable for decent results with my old Canon 2710.

 

[Nachkebia]

I just wish one day I will setup my enlarging system and I will never ever scan black and white again 😀

 

[markinlondon]

I just wish one day I will setup my enlarging system and I will never ever scan black and white again 😀

I've given my film scanner away now as I hadn't used it in three years.

 

[Trius]

My enlarger (currently in storage) has a diffusion/cold light head and I will never go back to condensor. Hence, my standard for developing film is to longer scale, which would make for even more difficult scans. Perhaps I shouldn't think about buying a dedicated film scanner after all. I suppose the option is, for important work that needs to be scanned, to do two scans to capture the entire range and put them together as layers or whatever in PS.