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KarimNassar

This video illustrates the biggest flaw of the bmcc perfectly

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I stumbled on this video and it displays perfectly the biggest flaw that I had the displeasure to work with on that camera:

 

https://vimeo.com/76824060

 

*** EDIT WITH WORKAROUND ***

 

There is a clever trick to work around this issue.

Thanks to Axel for digging it up.

 

Since the bmcc records raw, and when shooting raw you keep the actual recorded footage of the sensor, and an adjustment such as iso, is only kept written alongside the file in the metadata, what you can do is lower the iso until your image becomes decent.

 

In post you can then bring it back down to the native 800iso.

 

Not a perfect fix, as we would need to know how much of an increment we would need to exactly counter the screen displayed over exposure, but a nice workaround.

 

*** EDIT WITH WORKAROUND ***

 

 

When you work as a dp on a film,

 

You need the best visual feedback possible through the monitor in order to frame and work on your lighting adequately.

Does not need to be perfectly accurate, but the more the better, especially when working with lighting equipment to adjust your lighting.

You need proper feedback of how soft your fill light is, how strong your rim light and with what fall off etc...

 

And you need to have the vectorscope, as the visual feedback fools you in terms of recorded data, to get the best exposure possible on your camera, and make decisions on what you want to preserve, whether highlights or shadow or a balance of both, if the situation demands it.

 

Now with the bmcc, you have to extremely over expose your image to get best image quality.

The result is a completely washed out image through the monitor, good luck properly fine tuning your different lights with that.

 

And you have to disregard the vectorscope, because if you use it to expose properly you will actually be underexposed.

You have instead to completely over expose until you see zebras, meaning no proper control over exposure.

 

This is a major flaw, no professional camera should disregard the vectorscope and provide such inaccurate visual feedback.

 

Now let me know if I missed something here

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EOSHD Pro Color for Sony cameras EOSHD Pro LOG for Sony CamerasEOSHD C-LOG and Film Profiles for All Canon DSLRs

Vectorscope is for rgb levels, so what your really talking about is the contrast. I think the video is showing that even though the highs are way too high, in Raw you still have the data bring it all down and correct it. No one is gonna shoot over exposed like that on purpose!!

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Maybe I'm misunderstanding something, but the owner of the video clearly states that this is a test of how far he is able to overexpose in the field and still get great image - it is not intended as a guide to get the best image quality. I don't think you can use this as a reference to your particular experience of the BMCC, and the owner of the video clearly doesn't agree with you critique of the camera as he seems thrilled about the quality and handling.

Quote:
"This is a test to show how far to the right I can expose my Blackmagic Cinema Camera when shooting 2.5k raw"
+
"PS. The camera rocks."

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Vectorscope is for rgb levels, so what your really talking about is the contrast. I think the video is showing that even though the highs are way too high, in Raw you still have the data bring it all down and correct it. No one is gonna shoot over exposed like that on purpose!!

 

you think this is a show off video? As in look much I can overexpose and this amazing sensor holds all the information?

It is not. No sensor today can be that over exposed and retain highlight information to that extent.

 

There is something odd with that camera in that aspect.

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There are for sure, but still, this is a bit of an oversight if so black and white...

 

It is only that extreme when you open the footage in camera raw.

Camera raw does not interpret the footage correctly.

 

But when shooting you are heavily over exposing till you hit zebras and you are discovering what your footage actually looks like when you open it on the computer.

Which is a bad workflow imo and I have not experienced this with any other camera.

 

Maybe this video is to extreme to illustrate my point.

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Maybe I'm misunderstanding something, but the owner of the video clearly states that this is a test of how far he is able to overexpose in the field and still get great image - it is not intended as a guide to get the best image quality. I don't think you can use this as a reference to your particular experience of the BMCC, and the owner of the video clearly doesn't agree with you critique of the camera as he seems thrilled about the quality and handling.

Quote:
"This is a test to show how far to the right I can expose my Blackmagic Cinema Camera when shooting 2.5k raw"
+
"PS. The camera rocks."

 

I believe the owner is misunderstanding his camera.

He believes it holds heavily overexposed information and has the most extreme dynamic range in highlights ever.

Which is not the case of course.

It is because of this odd aspect of the bmcc where you cannot trust the vectorscope and you have to overexpose till you hit zebras.

You get overexposed feedback from your monitor when actually it is correctly exposed.

Zebras are actually the only correct information on overexposure, as long as they don't show, even if the vectorscope is off and the image seems heavily over exposed, you have highlight information.

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The intention of the video in the original post is to show how far to the right one can shoot in 2.5k RAW.. However, shooting this way does also produce the best image quality out of the camera.. This isn't directed at the original post but to the others talking about "the best image quality" from the BMCC.

 

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Sorry everyone made a mistake, everything I said is correct both from my experience and exposure recommendation from blackmagic forums.

 

But I was mislead by the author of the video as he states "straight from camera".

 

Since he then grades in camera raw, I believe his "straight from camera" is actually straight from camera raw.

 

Which accentuates the effect and is not a fair representation of the issue.

 

Edited the original post.

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The intention of the video in the original post is to show how far to the right one can shoot in 2.5k RAW.. However, shooting this way does also produce the best image quality out of the camera.. This isn't directed at the original post but to the others talking about "the best image quality" from the BMCC.

 

 

Perfect video to represent the issue thank you.

See the end of the video with the kitten:

 

over.jpg

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The intention of the video in the original post is to show how far to the right one can shoot in 2.5k RAW.. However, shooting this way does also produce the best image quality out of the camera.. This isn't directed at the original post but to the others talking about "the best image quality" from the BMCC.

 

 

Ok - thx

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Karim,

 

The BMCC gives you two basic monitoring options: Film and Video, which can be used for any recording mode. I think by monitoring in FILM Mode (log), you will get a much more useful monitoring image for the purpose of lighting  Was all this stuff monitored in Video Mode? It looks like it.

 

If you want to see all of the detail you are capturing, Film mode is the only way to go. It won't look pretty, and you may want to punch up the contrast and saturation on your monitor, but it's definitely better than looking at the over-exposed video mode monitor.

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In the comments to the ETTR video on vimeo, Majerski elaborates:

 

Because of how the Canon DSLR's have analogue gain - the dynamic range response is different with the ISO values and although much of the core explanation is the same, there would have to be some additional caveats in order to prevent any mis-information and or confusion.

 

I thought the only difference was the nature of the compression, that common DSLRs with mpeg4 codecs used internal raw interpretation before they compressed everything to a noisy mud. Am I wrong? I am more confused than before.

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The intention of the video in the original post is to show how far to the right one can shoot in 2.5k RAW.. However, shooting this way does also produce the best image quality out of the camera.. This isn't directed at the original post but to the others talking about "the best image quality" from the BMCC.

 

 

Great video from Tom there. I met him in Manchester last time he was over, really nice guy and knowledgable.

 

I am tempted to try this myself but how could we get around monitoring such an over exposed image as alluded to in the top post? The camera needs a ETTR mode!

 

By the way this only works with raw or 10bit ProRes, not worth trying with a compressed 8bit codec as it will create too much banding.

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I am tempted to try this myself but how could we get around monitoring such an over exposed image as alluded to in the top post? The camera needs a ETTR mode!

 

HurtinMinorKey says that in film mode you would get better monitor feedback.

I don't what we used on set as I was not the camera operator. Something to try.

 

Like you said this is the issue I am referring to, the best image quality comes with over exposing. 

They call it ettr which is common recommended practice with a lot of cameras, but in truth ettr on other cameras is never that extreme, on the bmcc really feels like overexposing until no zebras are seen.

The gain in quality is significant as opposed to correctly exposing using the vectorscope, it is well demonstrated in the video.

 

As of now utilizing this technique would be fine in daylight or situations where you don't control the light.

But when working with lighting the overexposed feedback becomes an issue.

 

Like you said and ettr mode would be the much needed fix.

A monitor feedback that compensates for the overexposure so you can work on your lighting properly.

 

Maybe some monitors can lower the exposure of the signal they are fed?

Not just lower the screen brightness as that would be useless.

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If you are doing ETTR at the native ISO 800 then switching to ISO 200 will give you the low noise, as it uses similar pull you will do in post on the ISO 800 footage, but in-camera.

 

ISO 200 on the Pocket looks great and don't notice the dynamic range being hurt, or worse highlights.

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Like you said and ettr mode would be the much needed fix.

A monitor feedback that compensates for the overexposure so you can work on your lighting properly.

 

Maybe some monitors can lower the exposure of the signal they are fed?

Not just lower the screen brightness as that would be useless.

 

 

I am tempted to try this myself but how could we get around monitoring such an over exposed image as alluded to in the top post? The camera needs a ETTR mode!

 

 

Probably the same Tom says on the BM forum:

 

Many people recommend exposing to the right in raw mode on the BMCC.

Sometimes when doing this, one finds the screen on the camera to be too washed out to be useful for composing your shot - in other words, the scene is exposed so far to the right without clipping, that the screen is almost just solid white. 

A solution to this is to lower the ISO value, as it will make the on screen image darker, but because its just meta data, the camera is still recording at ISO 800 - so no data is lost. 

 


That sets my mind at rest: In raw mode, you can use every ISO you want, without changing the exposure of the clip.

 

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If you want to use ETTR keep in mind that you should always try to achieve it first lowering your ND filter (if you don't want to change your shutter speed or shutter angle if you wan't to call it that way). Changing ISO depends on your camera, and what they call "sensor limited zone" where you start to loose Dynamic range in which case ETTR by boosting ISO above that value doesn't improve performance and you'd rather do it in post because you are loosing latitude. I don't know which value it is for the bmcc, maybe there is no gain going on in the converters so you should stay at base iso all the time. Does someone has the data?

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