DVX100 Contrast Ratio?
- Thread starter MrSleep
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Gary, contrast ratio and f-stops are the same thing. It's two systems of measurement what's being measured is identical. F-stops are merely ratios in powers of 2.
The tape records a digital signal. There's no limitation to that besides the format (issues in tape quality result in drop outs and unusable tapes, NOT in degraded image quality). So Barry's test is totally accurate. A 5:1 contrast ratio is absurd.
Of course, 7 stops of lattitude on video are mostly concentrated on the (very grainy) dark areas, film captures better the bright areas while the darks are just mud. So 7 stops of video lattitude may look worse than 7 stops of film lattitude.
The tape records a digital signal. There's no limitation to that besides the format (issues in tape quality result in drop outs and unusable tapes, NOT in degraded image quality). So Barry's test is totally accurate. A 5:1 contrast ratio is absurd.
Of course, 7 stops of lattitude on video are mostly concentrated on the (very grainy) dark areas, film captures better the bright areas while the darks are just mud. So 7 stops of video lattitude may look worse than 7 stops of film lattitude.
Scottdvx100
Veteran
I've never seen video resolve dark areas very well and yet will retains shadow detail very well.
Mr. Policar,
This is not just semantics. Contrast ratio is the ability (or range) for a device to distinguish the difference between light and dark. F-stops are simply a number. More specifically a fraction based on the lens diameter and focal length, that allows an amount light to hit the ccd's.
I reitierate my example:
Shoot 2 women in bright sunlight. One wearing a white dress the other wearing a black dress. I don't care what f-stop you use Video can not distinguish the contrast ratio like film or the human eye.
This is not just semantics. Contrast ratio is the ability (or range) for a device to distinguish the difference between light and dark. F-stops are simply a number. More specifically a fraction based on the lens diameter and focal length, that allows an amount light to hit the ccd's.
I reitierate my example:
Shoot 2 women in bright sunlight. One wearing a white dress the other wearing a black dress. I don't care what f-stop you use Video can not distinguish the contrast ratio like film or the human eye.
Baluardo
Well-known member
To measure the contrast ratio, shouldn't we fix iris and shutter and shoot at a scene which contains many levels of light (like in the kodak film tests) and see what is the range of light levels (in f-number) the camera is still able to reproduce between complete black and complete white? im curious to know if this changes from standard to cine gamma.
i would try it but i'm so damn busy at the moment..
Andrea
i would try it but i'm so damn busy at the moment..
Andrea
Baluardo,
I think your idea has merit but consider the end result. If you use the example that I posted before, you could use the camera to zoom in on the black dress and get an f-stop reading. You could then zoom in on the white dress and get that f-stop reading. When you pull out to include both, however, the lack contrast ability rears its ugly head.
That being said, what is the range (in a a scene) that is usable before you lose detail, color and overall image quality?
The other aspect that I spoke about earlier, is what happens when you go to tape?
I am not refering to digital tape but in fact the final viewing media. For myself whether its broadcast, cable or laptop monitor that's really the "meal ticket".
For the most part I must make aircopies on Beta SP which of course is analog, good analog, but still analog. . . and so are all the tv sets. This adds another level that screws with the problem.
My goal or perhaps my holy grail? . . .Lighting.
How much of a lighting ratio can we use to rival the ability of film (who has a greater contrast ratio) and still get good quality? Until the advent of these 24 and 30 frame cameras most have used the unflattering high key or very even lighting formula and never had to deal with this issue. Now we have cameras that create the feel of film it is only common sense to push the envelope for a creative edge.
Perhaps the final answer can be described in f-stop, but what is that range really?
Gary
I think your idea has merit but consider the end result. If you use the example that I posted before, you could use the camera to zoom in on the black dress and get an f-stop reading. You could then zoom in on the white dress and get that f-stop reading. When you pull out to include both, however, the lack contrast ability rears its ugly head.
That being said, what is the range (in a a scene) that is usable before you lose detail, color and overall image quality?
The other aspect that I spoke about earlier, is what happens when you go to tape?
I am not refering to digital tape but in fact the final viewing media. For myself whether its broadcast, cable or laptop monitor that's really the "meal ticket".
For the most part I must make aircopies on Beta SP which of course is analog, good analog, but still analog. . . and so are all the tv sets. This adds another level that screws with the problem.
My goal or perhaps my holy grail? . . .Lighting.
How much of a lighting ratio can we use to rival the ability of film (who has a greater contrast ratio) and still get good quality? Until the advent of these 24 and 30 frame cameras most have used the unflattering high key or very even lighting formula and never had to deal with this issue. Now we have cameras that create the feel of film it is only common sense to push the envelope for a creative edge.
Perhaps the final answer can be described in f-stop, but what is that range really?
Gary
Gary said:
First you say f-stops aren't quantitative enough, then you say that they are too quantitative so you want "really" instead. I don't know how to measure in "really" but "less than film and much less than the human eye" seems to be the most accurate measurement in totally qualitative terms.
F stops are ratios of light (well, T-stops are, but the two are virtually interchangable, and Barry measured using shutter speed anyhow--a more perfect test.) From that ratio, you can get a contrast ratio. Just raise 2 to the power of dynamic range in f-stops. Using 7 stops, that's 1:128, or about the 1:100 we would expect.
Letting "really" come into play, you may notice that you have to underexpose video more to get all 7 f-stops you want and that this will still look different from film even if film had the same number of f-stops. Realize also that even film shot during the day requires reflectors and can look far too contrasty. Even well lit movies have blown out windows all the time.
Still, all the 7 stops of data are going to be there, and if you want to drag down the top of the knee so that it's visible on all NTSC monitors, you could do that, since NTSC monitors seem to like to blow highlights even further. Or you could light differently or not worry about having 100IRE areas every once and a while.
Basically, you answered your own question with the lighting comment. If you don't like the "gamma curve" of video, light differently. If you can't light different, shoot 16mm.
Mr. Policar,
I especially like your last comment "If you don't like the "gamma curve" of video, light differently. If you can't light different, shoot 16mm."
It kinda sounds like if you don't want to speak English then go back to the country you came from.
Anyhow, if you're defending Mr. Green's test, great. Although if you really have read my posts, what Mr. Green tested was not my question. Unless, of course, you still believe that CONTRAST ratio and f-stops are the same thing. In which case this conversation can end here.
I especially like your last comment "If you don't like the "gamma curve" of video, light differently. If you can't light different, shoot 16mm."
It kinda sounds like if you don't want to speak English then go back to the country you came from.
Anyhow, if you're defending Mr. Green's test, great. Although if you really have read my posts, what Mr. Green tested was not my question. Unless, of course, you still believe that CONTRAST ratio and f-stops are the same thing. In which case this conversation can end here.
Gary, Policar is a respected member here and it would be best to refrain from personal attacks. His English is quite good - much better than many people.
He didn't say that contrast ratio and f-stops were the same thing. He defined the amount of difference between brightest highlight and deepest shadow in terms of the number of f-stops between the two (T-stops would, as mentioned, be the more appropriate terminology). As has been proven this can easily be converted to a ratio. There is nothing technically wrong with what has been presented.
He didn't say that contrast ratio and f-stops were the same thing. He defined the amount of difference between brightest highlight and deepest shadow in terms of the number of f-stops between the two (T-stops would, as mentioned, be the more appropriate terminology). As has been proven this can easily be converted to a ratio. There is nothing technically wrong with what has been presented.
dr_stupid
Active member
Funny, but I didn't think he was actually insulting your grammar. I thought he was saying that your suggestion (paraphrased: "if you can't get video to do what you want it to do, go back to using film") was similar to telling someone that if they can't speak English very well they should go back to the country they came from. Which would have been an analogy (rather than a personal attack) trying to make the point that he wants to learn how to improve his video results, not just go back to film. Gary? Am I wrong?
I love the debate, though. It's so far over my head, it makes me feel sophisticated!
I love the debate, though. It's so far over my head, it makes me feel sophisticated!
Hmmm...that makes sense. Well, I hope I'm not being an awful jerk then (I definitely don't mean to be one--I just don't respond well to personal attacks.)
The truth is, though, that video is never going to look exactly like film no matter how you light, and that film only looks good if it's decently lit. Personally I think high contrast looks fine, though. I love the look of War of the Worlds, for instance, which used beach bypass to emulate the look of video (I think.)
The truth is, though, that video is never going to look exactly like film no matter how you light, and that film only looks good if it's decently lit. Personally I think high contrast looks fine, though. I love the look of War of the Worlds, for instance, which used beach bypass to emulate the look of video (I think.)
discs of tron
Well-known member
clearly, gary didn't study the zone theory. no biggy. but if you want to some time, pick up ansel adams' book on that. policar's use of stops is pretty much in keeping with how any legitimate photographer or cinematographer uses the term.
and same with the ratio semantics thing. if we are comparing 2 devices, device A with a contrast ratio of 500:1, and device B with a 1000:1 ratio, then we would be totally accurate if we said that device B has one stop more of latitude.
and same with the ratio semantics thing. if we are comparing 2 devices, device A with a contrast ratio of 500:1, and device B with a 1000:1 ratio, then we would be totally accurate if we said that device B has one stop more of latitude.
Why would you call yourself Dr. Stupid? I think that was a pretty intelligent interpretation.
As far as to Mr. Discs of tron, thanks for your suggestion on Ansel Adams. I read his ideas in 1975 when I was a still photgrapher for a regional newspaper, (hint) unfortunately you are talking about film not video which does have quite a lot of latitude.
Let me ask the question in another language.
If you are shooting a scene (one scene) what is the maximum lighting ratio you can use and not get overblown whites or grain in the blacks? By the way this scene is set at one f-stop only let's say f5.6. In this lighting ratio we'll be using the Key light as the brightest.
As far as to Mr. Discs of tron, thanks for your suggestion on Ansel Adams. I read his ideas in 1975 when I was a still photgrapher for a regional newspaper, (hint) unfortunately you are talking about film not video which does have quite a lot of latitude.
Let me ask the question in another language.
If you are shooting a scene (one scene) what is the maximum lighting ratio you can use and not get overblown whites or grain in the blacks? By the way this scene is set at one f-stop only let's say f5.6. In this lighting ratio we'll be using the Key light as the brightest.
It's a pretty intelligent interpretation, but I'm not convinced it's what you had in mind. One phrase can have many connotations. But whatever.
That said, I think I've figured out where the issue of contrast ratio is coming up. The 5:1 figure you're quoting is probably the highest usable ratio of key light to fill light, while 100:1 is the traditional calculation for "contrast ratio." Anyhow, I haven't shot enough video to say for sure if that's true. A 5:1 ratio seems too high to me, but I'm certainly no cinematographer and at least it seems reasonable. I mean, I've seen movies that look like they were shot with no fill light (no detail on one side of the face) so it's a pretty qualitative thing you're asking and something that I don't know much about. But I think that's where the confusion is coming from.
That said, I think I've figured out where the issue of contrast ratio is coming up. The 5:1 figure you're quoting is probably the highest usable ratio of key light to fill light, while 100:1 is the traditional calculation for "contrast ratio." Anyhow, I haven't shot enough video to say for sure if that's true. A 5:1 ratio seems too high to me, but I'm certainly no cinematographer and at least it seems reasonable. I mean, I've seen movies that look like they were shot with no fill light (no detail on one side of the face) so it's a pretty qualitative thing you're asking and something that I don't know much about. But I think that's where the confusion is coming from.
dr_stupid
Active member
Gary said:
1. I'm a doctor.
2. I don't know much about video.
3. I always liked the Ren & Stimpy episodes featuring Stimpy as "Dr. Stupid," where he takes random dumb questions from the audience and spits out random dumb answers. See here for an example. Seemed sort of apropos for this forum, lest we ever take ourselves too seriously...
dr_stupid
Active member
Policar said:
Mmm - agree. Now I'm not convinced either. It's the tone that's throwing me off...
Hey Policar -- you do write quite well, incidentally. Also, I'm curious -- where are you studying film right now? Sounds like the curriculum is well-grounded in physics, not just art...
(sorry to take the discussion off topic yet again...)
thisiswells
Retired
Policar said:
I'd prefer not to take that comment literally, but it was clever and funny. I get what you are saying, of course. They are different mediums. Gary here appears to have just discovered lighting for video and it fascinates him. There are oodles of films shot on video that do look like film, including the lighting. Gary: Have you viewed the trailer for November? To my eyes, on a small monitor, it IS film.
So far be it for me to pretend to be some mega experienced, high in demand photographer. Truth is, if I were, I would probably not contribute here as much as I do. Though, I am hoping to change that soon...
I have witnessed a white / black contrast test and no-one here (so far as I can tell) is rebutting your remark of negative film capturing a broader latitude in that situation. However, no art director would ever create such an awkward contrast so it's moot.
Policar is a highly respected member of this user group, one who is naturally intelligent and equally well informed. He is deserving of at least a little kind recognition and community support every once in a while.
thisiswells
Retired
Good for you! I wish I would have done so well in HS. All those pesky internships didn't help much on my university applications! I'm 21, by the way.Policar said:
Brian