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Expert
Posts: 1,004
Registered: ‎01-10-2013
Message 31 of 92 (4,189 Views)

Re: Guide to Cine EI on the F5 and F55.

Added a simplified greyscale dpx - just horizontal 1-stop and 1/3 stop with 3IRE absolute black and 32IRE grey across the full width. Good for seeing how LUTs clip, shift or squeeze the camera's range.

 

S-Log2 Greyscale (zipped 10-bit .dpx)

Expert
Posts: 1,463
Registered: ‎11-20-2012
Message 32 of 92 (4,182 Views)

Re: Guide to Cine EI on the F5 and F55.

[ Edited ]

alisterchapman wrote:

Does it matter what meters or scopes I have, because the results will still vary because the gamma varies which means the effective density varies.

 

--------

 

So I take it that you don't actually have scopes or a light meter to see if the stuff you read about in a book or a white paper someplace really holds up in the real world?  I actually invested hard earned money in those tools and DSC charts  so that I could do my own testing and evaluations for myself to see what is really going on.  And I can tell you that your theories don't hold water.

 

And the rest of your post is a bunch of nonsense that just clouds the true issue (and relative simplicity) of actually setting the proper exposure on the F5/F55.  It ain't rocket science.

 

However, you are correct when you say "results will still vary because the gamma varies which means the effective density varies."    That is my point.   Real world testing must be done with the various camera setting combinations -- and those tests must be conducted and measured with the proper tools.  If one does not have those tools, then they are just talking about theory and should make that clear in their posts.

 

 

Expert
Posts: 2,283
Registered: ‎11-23-2012
Message 33 of 92 (4,159 Views)

Re: Guide to Cine EI on the F5 and F55.

Huh? I am completely confused by you Doug J.

 

When I stated in post 15 that "the effective density of video is different to that of film, so depending on the brightness and content of your scene you may see some variation between what a light meter tells you and what the camera tells you". and " it's worth checking the calibration of your light meter against the camera." You rather rudely dismissed it as "nonsense".

 

Now you agree that "results will still vary because the gamma varies which means the effective density varies." and that in your own words " Real world testing must be done with the various camera setting combinations".

 

Isn't that what I tried to say in the begininnig, variations in density effect exposure and as a result you should check your meter against your camera? But oh no, in your mind when I say it, it's nonsense. So come on Doug which is it, nonsense or not nonsense? Does density effect exposure or not, is it worth checking your calibration or not?

 

You don't actually appear to be clear yourself about how exposure and density works, if the density varies, the exposure range and mid point will vary, so as I stated right at the very begininng "you may see some variation between what a light meter tells you and what the camera tells you". This is not nonsense, not at all. This is why there are two different ISO standards for film and digital, one is ISO the other is EI and the two, while compatible need to applied slightly differently.

 

No, I don't need to list the light meters or test equipment that I own. Some of which I have left over from when I used to design first generation CCD video cameras because I doubt you would even know what they do. If that's not good enough for you then just ask some of the people on here that have attend my workshops whether I own a selection of lightmeters, WFM's and charts etc.

 

This conversation has been a complete waste of my time.

Expert
Posts: 1,463
Registered: ‎11-20-2012
Message 34 of 92 (4,147 Views)

Re: Guide to Cine EI on the F5 and F55.

[ Edited ]

Not surprisingly you just don't get it.  I have been nothing but consistent on this topic, and if you want to cherry pick a few lines of text out of a lengthy conversaion to show that somehow I haven't been consistent, then knock yourself out because that is a load of ******.

 

Just because 90% of SOME of your posts are nonsense, it is not logical to assume that your entire post is nonsense.  So don't assume that I take an oposite view of everything you say.  Do I have waste time going line by line through the posts?  I have more important work to do.

 

I refer you to my post #11 on this thread -- clear back on November 5th. 

http://community.sony.com/t5/F5-F55/Exposure-Issues-shooting-XAVC-1080p-HFR-120fps/td-p/229611

 

I have never posted anything that would be inconsistent with that post.  And if you go back here on this forum, and elsewhere on the web, you will find I have been saying the same thing for years about exposure and ISO on all the Sony cameras.  People must rate their camera for the exact mix of settings they have chosen and not blindly assume the ISO dsiplayed on the side of the camera is correct.  You have stated that the ISO is always correct.  Do you still stand by that?

 

You're not conistent about a lot of things you say and change your tune often -- and then act like that's what you've been saying all long.  I've seen it and so have others who have pointed it out to me privately -- but who don't care to incur your bullying and inevitable paragraph after paragraph of techno babble that quite often has no bearing on the actual topic at hand but is designed to shut the other person up.

 

This forum used to be a great place to exchange ideas and hear about the actual real-world experiences of others -- and who have the great work to back it up -- rather than just hearing the paraprasing of a technical manual over and over again and no decent examples of puttng those words into practice.

 

We can agree on one thing though, this convesation is a waste of time.

Specialist
Posts: 27
Registered: ‎03-25-2013
Message 35 of 92 (4,133 Views)

Re: Guide to Cine EI on the F5 and F55.

[ Edited ]

This is a very interesting point about the difference between how a light meter will react to film vs. video. If someone wants to research the technical facts infinitum far be it for me to argue. It's a bit misleading and in reality completely irrelevant. A meter reads foot-candles.  Fujifilm, Kodak film, raw, slog, 709. They all have different responses. You test for the exposure based on the look (exposure) you want and that is your base. Everyone tests there own iso range be it film or digital. The meter is relevent only to how it reads light. It's not rocket science unless you make it so.

 

 

 

Expert
Posts: 2,283
Registered: ‎11-23-2012
Message 36 of 92 (4,058 Views)

Re: Guide to Cine EI on the F5 and F55.

"I don’t see how you can single out film stock from any of the others."

 

Because the fundamental response of film is totally different to that of a CMOS or CCD sensor. All film is based on the same principle and all film has a toe, a shoulder and a central log response. A video sensor does not have a toe and rather than a shoulder just hard clips when overexposed. the response is linear. The linear response is then converted to the desired gamma response by processing which can have a multitude of different outcomes, log linear etc. The two systems are fundamentally different and as a result the way ISO or EI is determined is different.

Highlighted
Expert
Posts: 1,606
Registered: ‎11-19-2012
Message 37 of 92 (3,969 Views)

Re: Guide to Cine EI on the F5 and F55.

[ Edited ]

My recommendation if using a light meter with any digital camera is that you absolutely know exactly where middle grey is placed for the particular gamma curve being used.

 

For REC709 middle grey is around 45%, for slog on the F35 & F3 it is 38%, for slog2 it's 32%, for HG7 on the F55 it is actually 40% (not 32%), for Canon c-log it's 32%, etc..  John Hoare has published an excellent resource on the various middle grey levels for the F55 camera for those interested. (See: http://www.johnhoare.tv/f55gammas.htm ). The idea I have with all the different gammas and their placement of middle grey is that later in post it will be restored accordingly the "proper" middle grey value.

 

While you can chose to purposely place your reference grey point where ever you like, for example raising it in order to improve the latitude in the shadowed regions of the scene (pull proces in-camera) generally placement of middle grey should not just be arbitrarily chosen in the middle of the camera's sensitivity range or otherwise depending on the scene you could be robbing yourself of lattitude. If you do chose to move your middle grey point on a particular gamma curve intentionally (exact same effect as using CineEI mode to rate your camera's ISO lower) then further control of lighting must be considered as you will effectively reduce the latitude range in the opposite direction of middle grey.

 

As Alister points out according to ISO 12232:2006 there are in fact a variety of methods to determine ISO ratings for digital ISO which all makes for a better reaon why: 

 

  1. You can throw the ISO ratings by the manufacturer for various digital based SLR's and video cameras out the window. They actually don't mean anything in the real world except the lower the setting the better in terms of less noise. Generally they will come close to the ISO values of film.
  2. If you wish to work with a light meter and employ a "film style" approach to lighting for digital you should always perform your own camera "speed" rating so you can establish for yourself what ISO setting on your meter will correspond to the camera "seeing" middle grey when the f-stop on both your light meter and lens match up. Once you've established this point of reference from that point going forward all lighting becomes relative.

 

Funny enough the fact that each gamma curve DOES respond differently to different contrast ranges and the contrast distribution is not uniform, for me is even more reason why a light meter will help you to manage your lighting contrast ratios because looking at a waveform monitor you will have no clue for each gamma curve where for example 2.5 stops sits over or under middle grey, etc..

  

With your light meter (once calibrated to your camera system, lenses and settings) all you need to know is where middle grey is and you can work in stops and contrast ratios from there. ie. If you know a camera has 8 stops of latitude above middle grey and 5 stops below then that is exactly what you have and the underlying gamma being used really doesn't matter anymore as it's relevance is only how the contrast distribution takes place across the entire range of the signal for the purpose of optimal tonal reproduction of the image.

 

 

Expert
Posts: 280
Registered: ‎04-07-2013
Message 38 of 92 (3,959 Views)

Re: Guide to Cine EI on the F5 and F55.

Nicely put Dennis
Doug
Douglas Munro CSC
Expert
Posts: 1,463
Registered: ‎11-20-2012
Message 39 of 92 (3,958 Views)

Re: Guide to Cine EI on the F5 and F55.

[ Edited ]

starcentral wrote:

My recommendation if using a light meter with any digital camera is that you absolutely know exactly where middle grey is placed for the particular gamma curve being used.

 


Dennis we certainly have two different approaches.  Gray is not important to me at all.  I've shot enough test charts of the various gamma modes in the past week to last a lifetime.  And one thing that is abundently clear from all that testing is that the gray point doesn't matter very much because you can push that gray point around in Resolve to get it almost ahywhere you ultimately want it with virutally no ill effects.  And besides that, I really don't want to become dependent on carrying a gray card around with me and holding it up for every shot, or actually routinely using a light meter. A light meter is handy for testing, but I don't want to use it while shooting when there are easier ways of metering the exposure.

 

But what does matter to me, is white.  I expose for white and I need to know exactly where white is placed for the particular gamma curve being used.  If you blow out the whites, or even get them too high, the picture quality suffers quite a bit and, in the case of blown out highlights, may be unfixable.  Gray and black can do whatever they want, but white is the king and is much easier to measure than 18% gray.

Expert
Posts: 1,606
Registered: ‎11-19-2012
Message 40 of 92 (3,952 Views)

Re: Guide to Cine EI on the F5 and F55.

[ Edited ]

Yes the difference comes from the fact I would guess that you come from either an ENG or cameraman background where essentially you would expose for whites using zebras and let the rest fall into place  - whereas in a more film-like approach to lighting you would not do this. It's more about skin/grey value placement and managing lighting using ratios, etc..

Neither is wrong. But two entirely different schools of thought.

As with everything there are exceptions, for example when shooting with a linear gamma (like in RAW) because of the infinitely high level of data information at the upper end of the range. In this case shooting to the right, or over-exposed, or CineEi gain down, is preferred. But this nearly not as true when using conventional curve based gammas (ie. Rec709, HG, slog..)

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