Author Topic: A film's senistometric density curve and determining ISO (Read 17040 times)

Indofunk · « **Reply #50 on:** January 10, 2015, 11:01:43 PM »

Hey! I like that! Can I try? Ok, here goes ... how about the temperature at which you shoot the film? I sometimes shoot outdoors in the summer at 100(F) and sometimes in the winter at maybe the low teens (F), although being a cold wimp I try to avoid that

Francois · « **Reply #51 on:** January 11, 2015, 03:07:26 PM »

Unless you bring the film close to cryogenic temperatures, I don't think it would affect speed at all.
At high temperatures, it shouldn't be a problem until the emulsion starts to melt...

Terry · « **Reply #52 on:** January 11, 2015, 03:16:26 PM »

A curoius effect I've noted is that if I'm shooting in very cold weather (well below freezing, say) I don't usually notice the pain in my fingers until after I've made the last exposure....

Francois · « **Reply #53 on:** January 11, 2015, 03:45:13 PM »

That's the bad part for me. Shooting with mittens doesn't really work all that well

Bryan · « **Reply #54 on:** January 11, 2015, 04:23:58 PM »

I did read somewhere that you can get moisture on the film going from a cool air conditioned place to a warm humid place. just like the lens fogs up. I try to keep the camera acclimated when I'm shooting in hot humid places.

mcduff · « **Reply #55 on:** January 11, 2015, 04:48:31 PM »

Quote from: jharr on January 10, 2015, 10:42:50 PM

Any thoughts on how the curves change as film ages? Does the iso decrease in a linear fashion or maybe an inverse log?

That is a good question. The old "a stop per decade" always seems too easy and too linear. But now I think about it, given a stop is a geometric unit of measure (a doubling or halfing), I guess even with that example we are talking about its sensitivity changing in a geometric manner and not linear. Right?

I love that pic btw

moominsean · « **Reply #56 on:** January 11, 2015, 05:02:01 PM »

Remember...

Indofunk · « **Reply #57 on:** January 11, 2015, 05:23:19 PM »

Quote from: Terry on January 11, 2015, 03:16:26 PM

A curoius effect I've noted is that if I'm shooting in very cold weather (well below freezing, say) I don't usually notice the pain in my fingers until after I've made the last exposure....

My one roll session was taken at about 20F, and even just having my hands out to frame a single shot froze my fingers. By the end of the roll I was ready to check myself into a hospital for frostbite

But then again, my circulation is so bad that sometimes my entire left leg goes for days without blood.

Nigel · « **Reply #58 on:** January 11, 2015, 07:16:29 PM »

Right. I'm going to get a drink then I'm going to start back at the beginning.

That will shortly be followed by a stupid question - just warning you.

Indofunk · « **Reply #59 on:** January 11, 2015, 07:25:56 PM »

The more you drink, the stupider the question will be!

Francois · « **Reply #60 on:** January 11, 2015, 09:07:10 PM »

Quote from: mcduff on January 11, 2015, 04:48:31 PM

That is a good question. The old "a stop per decade" always seems too easy and too linear. But now I think about it, given a stop is a geometric unit of measure (a doubling or halfing), I guess even with that example we are talking about its sensitivity changing in a geometric manner and not linear. Right?

I love that pic btw

Actually it isn't linear since stops aren't from the start.

jharr · « **Reply #61 on:** January 12, 2015, 01:37:35 AM »

Well, one stop per decade is a linear (y = x where y is 'stops to add' and x is 'decades since expiration'). Since we are drifting away from actual pragmatism into theoretical perfection, might the actual film speed as calculated above, be different than the y = x equation?

Francois · « **Reply #62 on:** January 12, 2015, 03:12:17 PM »

Don't forget that each stop doubles the exposure. One stop might double, but two stops quadruple the exposure.

The real formula for stops is: exposure=2^(number of stops)

jojonas~ · « **Reply #63 on:** February 12, 2015, 10:06:58 AM »

I admit that I didn't do my homework

this is good how?

LT · « **Reply #64 on:** February 12, 2015, 11:56:06 AM »

BeJeebus! Filmwasters - you've changed.

Go to APUG, there is tons of this stuff over there

you'll fit in like a mouse in a field of mice.

Either that or make some lovely pictures. That's what we like here. Lovely pictures. Be creative, interpretive, critical and make pictures with film.

mcduff · « **Reply #65 on:** February 12, 2015, 01:24:04 PM »

Hey Leon don't abandon us kids for a while and come home complaining the kitchen is a mess! ;-p Plus it's not like we are talking digital or Katy Perry gossip. (Can I overuse ;-p ?)

But seriously, this question did come out of the quest to shoot. Occasionally I find a weirdo film (that was not intended for conventional still photography - such as a scientific or copy film) - sometimes you can find the curve for the film but not the ASA/iso info. I now know how to figure it out. Its nice to have a handle on what the box speed is before waste a roll or two. (There is good film wasting and bad film wasting after all. )

btw, I can't stand apug as these sorts of questions inevitably result in flame wars as the experts try to out-expert each other. I will try to label future topics with a 'nerd alert' prefix ;-)

Terry · « **Reply #66 on:** February 12, 2015, 02:01:18 PM »

I agree! The attraction of FW is in large part the absence of snipers here. We can have a discussion about useful-if-esoteric stuff like sensitometric curves and box speeds and seamlessly integrate it with pictures of pretty flowers. How much better can it get??? (Edit: and bunnies too.)

Late Developer · « **Reply #67 on:** February 12, 2015, 02:04:34 PM »

I'm genuinely sure that this tecchie stuff is vitally important, at some level. However (and I'm being serious) I am a troglodyte when it comes to such things and not at all sure how I'm meant to interpret the data or what it means in terms of what or how I photograph.

No way will I knock this as I simply don't understand it, but reading some of the content of this thread has proven how little I know about the science element (no pun intended) of photography. For me, it's enough to have a rudimentary knowledge of how to load the stuff into the camera and take photos.

Incidentally, what is a "Katy Perry"....?

Francois · « **Reply #68 on:** February 12, 2015, 02:40:26 PM »

Quote from: Late Developer on February 12, 2015, 02:04:34 PM

Incidentally, what is a "Katy Perry"....?

It's another one of those cute fuzzy bunnies... I think

mcduff · « **Reply #69 on:** February 12, 2015, 04:01:28 PM »

Quote from: Francois on February 12, 2015, 02:40:26 PM

Quote from: Late Developer on February 12, 2015, 02:04:34 PM
Incidentally, what is a "Katy Perry"....?
It's another one of those cute fuzzy bunnies... I think

If this is the case, Francois (and moominsean), is it too nasty for me to say "x²sinx=sinx³"?

LT · « **Reply #70 on:** February 12, 2015, 05:35:56 PM »

Quote from: Terry on February 12, 2015, 02:01:18 PM

I agree! The attraction of FW is in large part the absence of snipers here. We can have a discussion about useful-if-esoteric stuff like sensitometric curves and box speeds and seamlessly integrate it with pictures of pretty flowers. How much better can it get??? (Edit: and bunnies too.)

I know, I know. You are a fine bunch and I'm proud that you choose our little corner of the web-u-verse to share this kind of thing. Huzzah.

mcduff · « **Reply #71 on:** February 12, 2015, 07:21:15 PM »

Quote from: Leon on February 12, 2015, 05:35:56 PM

I know, I know. You are a fine bunch and I'm proud that you choose our little corner of the web-u-verse to share this kind of thing. Huzzah.

I am sure my family is glad I have FW as well as they put up with my nerding out less than folks here - and they don't just bomb me with flowers like James and Indo do!