For inquisitive minds only

[Anthony Carlsberg]

Any of you ever wondered if the weights of negatives/transparencies do change after exposure? Do they get lighter or heavier?

I realize that if they do it must be a miniscule amount but still I’d like to know your thoughts on the subject :-)) AC

[Jorge Gasteazoro]

No I have never wondered this. It does, it gets lighter, you remove silver to make the image either in color or B&W.....And you definitly have too much time on your hands, hope you are not in prision...:-)

[Geoffrey Swenson]

“hope you are not in prision...:-)” If not he should be!

Although this is intriguing question and not so much more irrational as some of them other occasional discussions. Where does all the silver go? Perhaps it evaporates and settles on the inside of the bellows introducing flare…No wonder for all that those fuzzy negatives :-(

[Larry Gebhardt]

If the exposed silver is elevated to a higher energy level (which I think it is) then the film will have gained mass. How much can be calculated from E=MC^2. I don't think you would be able to measure it with any balance on the earth. Also just warming it up a fraction of a degree probably adds more energry (mass) than exposing it.

[CP Goerz]

Its not just the film that gets heavier its the entire camera/holders/tripod/filters/lenses etc. Surely we have all noticed this on the way back to the car?



CP Goerz

[Jorge Gasteazoro]

If the exposed silver is elevated to a higher energy level (which I think it is) then the film will have gained mass



No, since the silver has been reduced to it's metallic state it gains the "mass" of an electron, but since when we fix we remove left over unreduced silver then the overall "weight" of the negative would be lighter...no?..



hmmm...perhaps I too have too much time on my hands....not in prision though..:-)

[Ron Bose]

I'm an engineer, so I apologize for sounding geeky ...

Following exposure to light, the mass of the film cannot change, how can it ? Light has no mass and therefore cannot add any to the film surface.

The molecules in the film do react on exposure to light but their overall mass does not change at all.

Now during the chemical reaction that happens during developing, then there is a transfer of material from the devloper to the film and vice-versa. So I'd say that the developed negative is lighter - especially as the anti-halation layer has been washed off the film.

All that said, I like answer from CP Goerz ...

[Philippe Gauthier]

I don't think so. When it by a photon, the silver halide crystal gains enough energy to change its structure, if I understand well. But if I remember well, it doesn't lose electrons or whatever, it only accumulates enough energy to change form. The mass of the crystal remains the same. Even if the photon somehow "merged" with the crystal, it wouldn't change its mass, as photons have no mass.

The processing of film, or course, removes a lot of silver and some gelatin, ehich affects the mass of the film. But I think that the impact of exposure alone is nil.

[Larry Gebhardt]

Ron and Philippe, photons do have mass, given that they have energy. Remember mass and energy are the same thing. Einstein theorized this, and it has been proven.

Jorge, you may be right - I don't fully inderstand the chemistry of exposure. I think we can agree though that if energy has been added or removed from the system, then the mass will have changed.

Certainly after development the mass will have changed, but that is not what the original question asked.

[Philippe Gauthier]

Mass can be turned into energy and vice versa. But mass isn't the same thing as energy. In that case, E=MC2 wouldn't make any sense, because the equation would have twice the same terms (Energy and Mass) and that equality sign wouldn't hold. Photons carry energy, but have no mass by themselves. I understand that when they hit a silver halide crystal, this energy is not converted into mass, but just transfered to the molecule - a few electrons change their orbit and that's it.

[Kerry L. Thalmann]

Photons carry energy, but have no mass by themselves.

This is correct, and according to Einstein's theories photons (or anything else) can only travel at the speed of light if they are massless. Only on science fiction shows like Star Trek do bodies with mass travel at (or beyond) the speed of light.

Kerry

[Steve Baggett]

The emulsion would increase in mass by a tiny, tiny amount. The siliver halide crystals' shared electron clouds would "capture" (some of) the photons and change their internal quantum mechanical state, moving to a slightly higher energy level. The resultant mass change would be equal to (in the MKS system) the captured-electron-energy (in newtons) divided by the speed of light squared. The demoninator is very large (9x10^16 m^2/s^2) and the numerator has to be very small, also. The resultant mass change is probably less than the mass of one electron. Somebody out there calculate the lux-seconds exposure for 18% gray on 100ASA film which gives your favorite density for that (in logD), then covert this to MKS and divide by 9x10^16, and you will then have your answer, in kilograms. Me, I'm going to go watch the X-files with no lights on and leave the calculations to bigger geeks.

[Jorge Gasteazoro]

LOL...glad to see I am not the only one with all this time on my hands...:-)

[Geoffrey Swenson]

LOL...glad to see I am not the only one with all this time on my hands...:-)

But look at the bright side! Do appreciate these priceless (I wouldn’t say useless) tides of information to broaden our horizons. Additionally, all this time spent on threads like this prevents us to make bad and boring photographs and thus the hapless public and we all benefit :-)))))

[Kevin Crisp]

Linhof is working on a device to compensate for this. It is very, very expensive.

[Ryan M]

My film definately gets heavier when I make an exposure. Its all the !@#$%^&*( dust that attaches itself to the film. Its like some freaky parasitic mating ritual.

[Jorge Gasteazoro]

hmmm..you know now that I think about it, I think it does get heavier after exposure, must be the reason the effing backpack is twice as heavy going back to the car than it was leaving it...:-)

[d.s.]

So does gamma, which I heard constantly bombards the earth and adds to the fog of film, also lighten the weight of film? Or ...

[Kevin Crisp]

Film gets lighter, but only when the fog is lifting.

[Jon_2416]

Not true Kerry!

>Only on science fiction shows like Star Trek do bodies with mass travel at (or >beyond) the speed of light.

Every time I walk into B&H all the cash in my wallet disproves Einstein... it flies into their cash register at SEVERAL times the speed of light!

[John Kasaian]

Gee, this question sounds familiar. FWIW, I always defer these kinds of issues to http://britneyspears.ac/lasers.htm

[Jean-Louis Llech]

A similar question was asked at the end of the XIX° century :
Some scientifics measured the weight of a human body just before and immediately after death : the difference of weight was supposed to correspond to the weight of soul.
Do you think that, after being exposed, the negative has obtained or lost a soul ?