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all type of film have seven stops lattitude?


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#1 YongLee

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Posted 03 June 2007 - 08:10 AM

i will shoot a 35mm film in next month. i have shoot movie in HD several , but use film is my first . i want to know if all type of film have same lattitude , seven stops , up 3 and down 4 between the middle gray. can you help me ? thanks!
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#2 Laurent Andrieux

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Posted 03 June 2007 - 08:51 AM

Not really. Historically, the older stocks used to have 3 under, 2 upper the middle grey (equivalent to point 11 of the lumination on the X axis of the H and D curve). Nowadays it's more like what you describe but some "low contrasts stock" like 5229 have a bit more. The point is it depends a lot on the whole process : will you time traditionnally (film only process : print), edit and time on a computer and go back to positive film ( scan and shoot) or plan to produce a digital master for TV release only (and is it HD since there is a special film for this purpose) ? The negative itself can have more information that 7 stops latitude but the way you time and master will let show more or not... (Sorry for my bad english).
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#3 Jonathan Bowerbank

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Posted 03 June 2007 - 12:50 PM

3 over you can still pull back and get a good image, but 4 under you really have VERY little information to play with. 4 stops underexposed is usually quite black. But if we're talking about intercuttability latitude, your margin of error is even tighter.

Subjectively, from my POV, there's a range of 1/2 under to 2 over that's still intercuttable when timed back to normal. More than 1/2 under and the grain is intolerable when timed back, by my standards.
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#4 Laurent Andrieux

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Posted 03 June 2007 - 05:38 PM

We're not talking about "how many stops can I over/underexpose and still have a good image if I correct in post", here, are we ? When I mean 3 or 4 stops under I mean that if you read something with a spotmeter that is 3 o 4 stops under KL, it will be black but still have a little detail (I'd say 4 stops you reach the toe).

At least, any stock is supposed to reproduce the 6 values from black to white with a 2 factor of their reflectance (black : 2.5 %, 5%, 10 %, 20%, 40 % and 80 % for white)

Of course Jonathan's considerations are good but I really think the whole process matters a lot. The proper answer is : make tests !
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#5 Michael Nash

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Posted 04 June 2007 - 12:20 AM

We're not talking about "how many stops can I over/underexpose and still have a good image if I correct in post", here, are we ? When I mean 3 or 4 stops under I mean that if you read something with a spotmeter that is 3 o 4 stops under KL, it will be black but still have a little detail (I'd say 4 stops you reach the toe).


This is a huge problem that never seems to go away. Latitude is the amount you can over- or under-expose a film stock and still be able to recover a useable image. Let's not confuse this with "dynamic range" or other similar terms that describe the range of brightness that a film can capture. It's erroneous and misleading to use the term "latitude" when describing the amount of highlight or shadow detail a given film can capture.
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#6 Laurent Andrieux

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Posted 04 June 2007 - 04:16 AM

Okay, I assume Yong Lee was asking about the "range" not latitude then... Thanks for clearing that up, Michael. For what is about latitude, I would second Jonathan too, anyway (1/2 under, 1/2 upper, max).

Yong, were you asking about what Michael describes as latitude or dynamic range ?

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#7 John Holland

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Posted 04 June 2007 - 10:41 AM

we are talking neg here not reversal ? 1/2 stop under should be not any prob . 4 under yes and 2 stops over no prob either .
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#8 Laurent Andrieux

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Posted 04 June 2007 - 10:58 AM

By 1/2 I mean one or two, not half a stop... I guess that is what Jonathan was meaning as well... Well may be he was meaning half a stop under... Well I think you have at least one in fact but it all depends on what is on the negative as well (and its contrast...) Talking average is never very valuable...
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#9 Jonathan Bowerbank

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Posted 04 June 2007 - 01:04 PM

By 1/2 I mean one or two, not half a stop... I guess that is what Jonathan was meaning as well... Well may be he was meaning half a stop under...


Yeah, just IMHO anything more than 1/2 under is hard to correct back to anything that's properly or overexposed. The grain is just too much at a full stop under. But yes, half a stop under and 2 stops over is what I meant :)
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#10 Laurent Andrieux

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Posted 04 June 2007 - 02:27 PM

Well that really depends on the timing route I think, if you print traditional, and as you mentionned, as for the "intercuttability latitude", I agree but with a DI and if the whole sequence is underexposed 1 or 2 stops, you may get something acceptable, even grainy or for a night effect for instance, depending a lot on the whole image but, again I think the topic starter was asking about the film's dynamic range, rather than its latitude.
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#11 Igor Trajkovski

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Posted 04 June 2007 - 07:56 PM

...again I think the topic starter was asking about the film's dynamic range, rather than its latitude.



I think the same.



Regards

Igor
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#12 YongLee

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Posted 08 June 2007 - 10:37 AM

oh ,thanks !
in my POV, the dynamic range is equal to lattitude, but i know it is wrong. can you explain to my,thanks!
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#13 Laurent Andrieux

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Posted 08 June 2007 - 04:08 PM

Ok, let's try to. I'll begin and, of course, other people will complete etc.

1) Read Nathan's post.

Dynamic range is, as he says, "the range of brightness that a film can capture". Imagine a field, action etc., where you have different brightness values, from "black" to "white". The question is, according to the contrast that is actually in the field, will film record this ?

If it's only a black to a white board contrast, a 6 stops dynamic is good enough to record (and potentionally reproduce) it. But imagine a very contrast field, like the one you'd get with a subject in front of a window. The highlights may be more than 3 or 4 stops over the keylight, while the blacks in the foreground may be 3 or 4 stops under.

Of course, that takes account of the albedo of the subject. But, whatever this albedo is, and according to the lights that illuminates it, the object looks black or grey or white.

The dynamic range is the contrast ratio beetween lowest and highest brightness that the film will be able to record.

You certainly admit that there is a need for a minimum brightness so that the film reacts, as well as there is an amount of object's brightness that is high enough, that even if it was even brighter the film wound't be able to record any difference, and it would be seen at white. Well, the dynamic range is that contrast ratio.

The latitude depends not only of the film stock but also on the field/object contrast. It is the error margin for exposing one can consider when shooting that can be corrected afterwards (timing). Is it a problem if I underexpose 1 or 2 stops ? Can I overexpose 1 or 2 or 3 stops ? This is what latitude tries to answer to.

2) Read Jonathan's posts

What Jonathan says is : you can underexpose half a stop, while you can overexpose 1 or 2 stops with no problem. As he says, "(Subjectively, from my POV), there's a range of 1/2 under to 2 over that's still intercuttable when timed back to normal".

I may have puzzled you since I mentionned the fact that one may want to deliberaly under/overexpose for a particular purpose, but the latitude is basicaly the margin error you have when you expose. If the subject is low contrat, you have more latitude. If the object is already using the whole dynamic range, let's say 6 or 7 stops, then you have less latitude.

Am I helping you out ?
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#14 Evan Winter

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Posted 08 June 2007 - 06:08 PM

Dear Yong Lee,

All newer color negative film stocks:

dynamic range: 10 stops+
underexposure until black: approx 3-4 stops under
overexposure until white: approx 4-5 stops over
typical practice: overexpose the film by 1/2 - 3/4 of a stop for a denser negative (can be manipulated more in post and will result in less grain)

Hope this helps. Good luck with your shoot.

evan
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#15 YongLee

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Posted 09 June 2007 - 08:21 AM

thank you very much , I see completly!
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#16 rohtash chandel

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Posted 12 June 2007 - 06:36 AM

3 over you can still pull back and get a good image, but 4 under you really have VERY little information to play with. 4 stops underexposed is usually quite black. But if we're talking about intercuttability latitude, your margin of error is even tighter.

Subjectively, from my POV, there's a range of 1/2 under to 2 over that's still intercuttable when timed back to normal. More than 1/2 under and the grain is intolerable when timed back, by my standards.

hey jonathan could you please eloborate intercuttability latitude, never heard of it :huh:
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