The challenge of exposing the Helium sensor

[Jacek Zakowicz]

Yes compared to Alexa at same iso and t-stop and fps/shutter, red appears about a stop darker at default red settings, so 1250-1600 on red looks like 800 Alexa on the monitor

That would explain why we see so many under exposed images since a lot of DPs use their trusty light meters to read the set lighting.

 

[Stacey Spears]

That would explain why we see so many under exposed images since a lot of DPs use their trusty light meters to read the set lighting.

I would argue that we see a lot of under exposed images because many are not using a light meter at all. I see more and more people using the tools in the camera instead of a light meter. All of the latest cameras have some great tools, but you should still use a light meter.

I have used the default profile in my Sekonic with Dragon and seem to get properly exposed images. I would like to try creating a custom profile for Sekonic and Dragon just to see if I can eek out as much as possible.

 

[Björn Benckert]

This is nothing new is it? Check your goal posts, check your stoplights, check your histogram at 800ISO no color setting. if the histogram is fat no goal post is raised and there is no stoplight, usually then you got a pretty good chance of getting a fat capture. Then sure you got those moments when exposure is wider than that and you have to decide what to clip or dip in the dark, then HDRx comes handy. But usually I think the DR is more than enough usually better to adjust the light then go HDRx.

Was up in the alps last week on a recce and brought helium and a canon zoom... the touch screen was impossible to see if it was on on or not due to the light, but covering it with my jacket I managed to dail in F22 and something like 10deg shutter and 50fps, that gave me good coverage in the white sunlit snow. possibly not the best way to shoot but atleast my exposure was dead on

 

[Elsie N]

This is nothing new is it? Check your goal posts, check your stoplights, check your histogram at 800ISO no color setting. if the histogram is fat no goal post is raised and there is no stoplight, usually then you got a pretty good chance of getting a fat capture. Then sure you got those moments when exposure is wider than that and you have to decide what to clip or dip in the dark, then HDRx comes handy. But usually I think the DR is more than enough usually better to adjust the light then go HDRx.

Was up in the alps last week on a recce and brought helium and a canon zoom... the touch screen was impossible to see if it was on on or not due to the light, but covering it with my jacket I managed to dail in F22 and something like 10deg shutter and 50fps, that gave me good coverage in the white sunlit snow. possibly not the best way to shoot but atleast my exposure was dead on

Perhaps because I'm not a big fan of shallow depth of field, I adjust light via f-stop all the time when shooting brght sunlight non-critical stuff.

Indoors I find you just have to open up the lens but outdoors, somewhere up to f-11 can give me quick-turnaround image.

I'll use an ND, but prefer the f-stop method of clipping management.

 

[Jacek Zakowicz]

I would argue that we see a lot of under exposed images because many are not using a light meter at all. I see more and more people using the tools in the camera instead of a light meter. All of the latest cameras have some great tools, but you should still use a light meter.

I have used the default profile in my Sekonic with Dragon and seem to get properly exposed images. I would like to try creating a custom profile for Sekonic and Dragon just to see if I can eek out as much as possible.

If your light meter reading does not match the camera sensitivity by one stop you will under expose by one stop if you are setting the lens aperture/shutter speed according to your light meter reading. Am I missing something? Other than the goal posts that- you must admit, many could find confusing especially with the ETTR vs ETTL argument ;-) It's like a moving target...
Also for someone that only uses Red cameras it is second nature after a while but for people trying to pick the tool for the job staying brand agnostic it may be a surprise that they need to put in a one stop correction compared to other cameras... one could make a strong argument to adhere to standards....
BTW that's exactly what happened in that latest Helium VS ARRI comparison:
Helium got under exposed because the testers assumed that both 800 ISOs would match.
Oh yes- I rest my case ;-)

 

[Florian Stadler]

I did side by side with an Alexa mini and a light meter and indeed Helium is a full stop darker at the same ISO. Reds ISO rating is an alternative fact (lie) for marketing purposes and should be adressed. There are clear established measuring techniques and other camera manufacturers seem to be able to follow it while Red seems to rely on the fact that no one uses a light meter or another camera at the same time.
Don't get me wrong, I love the Helium Weapon for it's resolution and sensitivity. Yet I don't like that the ISO is mislabeled gravely. My solution to this problem is that I have developed a LUT that is based of the IPP2 preview and matches exposure with the Alexa so I can shoot them side by side at same stop and ISO setting (640 is my preference, pushing it to 1280 through the LUT). I have publicly asked in a thread with Graeme my beef with the ISO mislabeling and i have been ignored so far. Maybe I need to take the time and publish those tests...

 

[Steve Sherrick]

If using a light meter, you might want to consider profiling that meter specifically for the camera you are using.

Ryan Walters has some info on that here.
http://indiecinemaacademy.com/create-sekonic-dts-profile-light-meter-video/#tab-id-2

 

[Stacey Spears]

If your light meter reading does not match the camera sensitivity by one stop you will under expose by one stop.

I agree with you. In testing I ran with the folks at DP Review, the VV Dragon matched the Sekonic L-478D light meter on their test chart wall. Did not have a Helium or ARRI to test, so can't speak to them.

 

[Josiah Duncan]

I did side by side with an Alexa mini and a light meter and indeed Helium is a full stop darker at the same ISO. Reds ISO rating is an alternative fact (lie) for marketing purposes and should be adressed. There are clear established measuring techniques and other camera manufacturers seem to be able to follow it while Red seems to rely on the fact that no one uses a light meter or another camera at the same time.
Don't get me wrong, I love the Helium Weapon for it's resolution and sensitivity. Yet I don't like that the ISO is mislabeled gravely. My solution to this problem is that I have developed a LUT that is based of the IPP2 preview and matches exposure with the Alexa so I can shoot them side by side at same stop and ISO setting (640 is my preference, pushing it to 1280 through the LUT). I have publicly asked in a thread with Graeme my beef with the ISO mislabeling and i have been ignored so far. Maybe I need to take the time and publish those tests...

IIRC, Red iso ratings are closer to Kodak than Arri. There's no standard that everyone has to conform to, but if there was I would imagine it would be based on film stock of some kind. Regardless, if you're depending on a light meter one would expect it to properly profile and calibrate it based on the stock/camera.

 

[Kenneth C Merrill]

- 4 stops ?


Solving the challenge:

Proper exposure, black shading & WB.

This is exactly what I'm saying. If the shadows always shift green on the Helium, then I sure as heck don't want to be rating the sensor at 3200 ISO because even a properly exposed image at that rating will start to shift green. But I'm also being told that to get good highlight protection (like the Alexa), then I have to rate the sensor at 3200 ISO. It's a catch 22.

 

[Jacek Zakowicz]

IIRC, Red iso ratings are closer to Kodak than Arri. There's no standard that everyone has to conform to, but if there was I would imagine it would be based on film stock of some kind. Regardless, if you're depending on a light meter one would expect it to properly profile and calibrate it based on the stock/camera.

That's interesting- did not know that. Do you have a source for that?
BTW I may be wrong but the posts above of the tests and comparisons seem to contradict it- meters seem to be matched to ARRI rating. Correct me if I'm wrong please.

 

[Hrvoje Simic]

This is exactly what I'm saying. If the shadows always shift green on the Helium,

...

Where did you get that ?

But I'm also being told that to get good highlight protection (like the Alexa), then I have to rate the sensor at 3200 ISO. It's a catch 22.

3200 is a two stop push, you posted a 4 stop push with zero info on shooting setup/conditions and development process. If you plan a 4 stop push and deciding on a camera based on that please re-consider the profession.

There is a catch 23.

You can do your own tests with your camera, measure its usable range, use a light meter and design the light so it fits Helium DR distribution. So you don't have to push your camera to seem as if it is another camera and just light for your own camera.

It's been done successfully many times before with cameras of much smaller DR and shitty recording codec.

 

[Jacek Zakowicz]

Where did you get that ?

You posted an example with 4 stops pushed image with zero information on shooting conditions and development process.




There is a catch 23. Much cooler than 22.

You can do your own tests with your camera, measure its usable range, use a light meter and design the light so it fits Helium DR distribution. So you don't have to push your camera to seem as if it is another camera and just light for your own camera.

It's been done successfully many times before with cameras of much smaller DR and shitty recording codec.

Using this logic every time I buy a tool I have to test it and determine what range of parts it would work for:
Guess what- when I buy a 17mm wrench I can be pretty confident it will work on 17mm bolt. It's called "standard"... for that very reason ;-)

 

[Hrvoje Simic]

Using this logic every time I buy a tool I have to test it and determine what range of parts it would work for:
Guess what- when I buy a 17mm wrench I can be pretty confident it will work on 17mm bolt. It's called "standard"... for that very reason ;-)

Wrong analogy Jacek.

Each camera differs in DR distribution, colorimetry, noise floor, shadow performance, highlight performance etc. and numbers on a paper alone are insufficient to get to know it and use it properly.

 

[Jacek Zakowicz]

Wrong analogy Jacek.

Each camera differs in DR distribution, colorimetry, noise floor, shadow performance, highlight performance etc. and numbers on a paper alone are insufficient to get to know it and use it properly.

Unless you imply that there is actual sorcery involved the numbers on paper ought to be sufficient to use any technical device properly by a competent operator.
Simply because they were designed in a "numbers on paper " way by equallly competent , or more competent engineers and designers. BTW I'm speaking from experience- I have done it every day for 25 years... design that is ;-)

 

[Kenneth C Merrill]

Where did you get that?

The shadows have always tended green in my footage. They dramatically shifted green in the test I posted (shot by someone else). They shifted green in John Marchant's (from Kipper Tie) dynamic range tests. Hell, they even shift green in Phil Holland's extensive Dragon v. Helium tests.

I mean, have you been watching any of this stuff? It's not just a one-off fluke.

No matter what exposure strategy you use, no matter how you rate the sensor, you're going to end up shooting a scene that has shadows. If those shadows shift green when they shouldn't, then there's a problem--and that seems to happen a lot on this camera.

The reason I posted that -4 stop image in the OP was to show how dramatic that shift is. Even if you don't push your footage in post (which I really never do anyway), you will have parts of your image that are 4+ stops underexposed (shadows), and that pushed image in the OP shows JUST HOW GREEN THOSE SHADOWS ARE.

 

[Kenneth C Merrill]

Using this logic every time I buy a tool I have to test it and determine what range of parts it would work for:
Guess what- when I buy a 17mm wrench I can be pretty confident it will work on 17mm bolt. It's called "standard"... for that very reason ;-)

EXACTLY!

No one is saying you shouldn't get to know your camera before you shoot with it. What we're saying is that ISO is an actual international standard that has objective, measurable parameters. If you're going to use the label "ISO" with your system, then you have to accurately describe its performance, otherwise you're basically deceiving the operator, who will assume (rightly so) that when you say "800 ISO" you mean the same kind of sensitivity/luminance output as everyone else who correctly applies ISO parameters and correctly labels their output levels.

 

[Hrvoje Simic]

Unless you imply that there is actual sorcery involved the numbers on paper ought to be sufficient to use any technical device properly by a competent operator.
Simply because they were designed in a "numbers on paper " way by equallly competent , or more competent engineers and designers. BTW I'm speaking from experience- I have done it every day for 25 years... design that is ;-)

Okay...let's put it this way.

Which numbers on paper exactly do you find lacking in this case and presented with other solutions, which alone would prevent one from underexposure, burned highlights, noisy footage and weird colour shifts ?

 

[Jacek Zakowicz]

Okay...let's put it this way.

Which numbers on paper exactly do you find lacking in this case and presented with other solutions, which alone would prevent one from underexposure, burned highlights, noisy footage and weird colour shifts ?

You are the expert (unless you imply you are a sorcerer ;-) and I'm not a camera operator. Or an electronic camera designer for that matter...
Look you aking for my opinion....it is completely irrelevant. Only Red knows the core of the matter. I'm sure they want to address it more than anyone.
I only pointed out one obvious issue (ISO discrepancy) that may contribute to the exposure difficulties the OP is having ...
Hope that's clear...

 

[Michael J Brennan]

Quote Originally Posted by Josiah Duncan View Post
IIRC, Red iso ratings are closer to Kodak than Arri. There's no standard that everyone has to conform to, but if there was I would imagine it would be based on film stock of some kind. Regardless, if you're depending on a light meter one would expect it to properly profile and calibrate it based on the stock/camera.

In the world of video, there has been standardised testing system for three or more decades.
You have a S/N number.


But no let's use a system designed for chemical process!


If the camera has waveform, histogram (aka internal light meter) you don't even need to know its ISO number.



Mike Brennan