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Epic Sensor Questions

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JamesM

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Hey guys,

Firs time posting on this forum and just had a few questions about the Epic. I have a shoot coming up next (29-30th) weekend where I will be focus pulling on the camera and wanted to clear up a few basics. I have had a poke around the forum and Google to try and find answers (including reading over 10 pages of the Q & A thread), but have not found completely clear answers for the following. Hopefully this thread may be useful to other people working with the camera for the first time.

1. Is the epic sensor identical to the Red One M-X sensor?

2. What is the film size equivalent e.g. 35mm, S35mm and so forth? And is it exactly the same size, or just approximate, i.e. what size would you use for depth of field calculations?

3. What is the circle of confusion for the Epic, and does it change as you adjust the project resolution?

4. Does anyone have a webpage that does Epic depth-of-field calculations, not an iPhone app?

5. Does the depth of field change as project resolution changes?


I'm going through the manual for the second time at the moment but just wanted to clear these few basic up first. Thanks in advance for any help - there will probably be many more questions to come!
 
Last edited:
Good luck with your shoot today . . .
 
i have few more questions about sensor size also..
why we call this sensor as a full frame since its same sensor with red one mx which is equivalent to 7D (APS-C) sensor..
why its 96 FPS max at FF? why not 100..clients gets confused when they heard its 96fps and asking same question whats special with 96 why not 100?
 
Kemalettin Sert said:
i have few more questions about sensor size also..
why we call this sensor as a full frame since its same sensor with red one mx which is equivalent to 7D (APS-C) sensor..
why its 96 FPS max at FF? why not 100..clients gets confused when they heard its 96fps and asking same question whats special with 96 why not 100?
Click to expand...

Because 96 is actually the maximum at 5K FF.

5k FF means the Full Frame of the Epic S35 5k sensor.
 
Deanan said:
Because 96 is actually the maximum at 5K FF.

5k FF means the Full Frame of the Epic S35 5k sensor.
Click to expand...

Is 96 the limit for ever or will it increase to 120fps in later builds.

I also find 5K FF confusing as FF is Red's designation of a vista-vision 8 Perf format, or was a couple of years ago.
 
#2. Steven Hilder previously posted this chart. Not sure it has ever been 100% confirmed by RED.

mysteriumx.png


#4. There are a lot of on-line DOF calculators. Here is one: http://www.dofmaster.com/dofjs.html

Select the Circle of Confusion (CoC) that is the closest to the EPIC resolution you are shooting. Several people have posted how to calculate CoC. e.g. take the diagonal measurment and divide it by 1730 or 1500. For 4800x2700:
29.74 / 1730 = 0.01719
29.74 / 1500 = 0.01982
 
1. Yes, but the Epic records the full sensor (5K), whereas the RED MX (4K) reserves a border around the edge of the sensor for look around room that is not recorded.

2. According to the RED website Epic at 5K is the same as S35, but I believe that it is actually slightly larger than S35 film. For depth of field calculations the difference is probably negligible: http://www.red.com/products/epic

5. The sensor size is cropped as you go down in resolution, so the sensor gets smaller. This doesn't technically change the depth of field, but since you will have to use wider lenses or step back from the subject to compensate, you will in practice have deeper focus. 2K on the MX sensor is similar to S16 film.
 
Deanan said:
Déjà vu:
http://www.youtube.com/watch?v=EbVKWCpNFhY
Click to expand...

Great, I just spit my coffee all over my laptop... Brilliant analogy Deanan!

This may sound stupid. but why all the 4K recording modes? Isnt that reducing the resolution?

Is there a crop factor like shooting 2K I presume? Do we have a chart for that?

Do people still shoot 4K HD because of its clean math to a 1080P deliverable?

5K 2:1 seems more logical to use most of the time.
 
Kemalettin Sert said:
yes Deanan i know max is 96 but why not 100?
Click to expand...

Because of the bandwidth limitations of Epic-X hardware, which is considerably less constrained than Red One hardware.

If it will comfort you or your clients to work only with round numbers at full resolution, then perhaps you should limit your fps to 50 or 75 or 90. ;-)
 
Bill Goehring said:
Because of the bandwidth limitations of Epic-X hardware, which is considerably less constrained than Red One hardware.

If it will comfort you or your clients to work only with round numbers at full resolution, then perhaps you should limit your fps to 50 or 75 or 90. ;-)
Click to expand...

actually i dont have any problem with 96 number..said many times its cuz of limitations of image processor is not enough for some people..
 
Stephen Williams said:
Is 96 the limit for ever or will it increase to 120fps in later builds.

I also find 5K FF confusing as FF is Red's designation of a vista-vision 8 Perf format, or was a couple of years ago.
Click to expand...

How about using/calling it 5K FS for full sensor?
 
I suspect the camera was designed with specs for 24p film making (and 23.98 NTSC) so us poor PAL people miss out.

It would be great to have a S35 size 100 at 25p. I've lost count of how many times this comes up on commercials (whole frame divisible frame rates for frame cutting and ramping).

I'm hoping maybe for a 5K 16:9 mode (maybe at 4900 x 2600 or whatever the ratio is) basically enough vertical scan reduction to win back the extra 4 frames.

Can we make that a wishlist request?.......:)
 
Jeff Brown said:
I suspect the camera was designed with specs for 24p film making (and 23.98 NTSC) so us poor PAL people miss out.

It would be great to have a S35 size 100 at 25p. I've lost count of how many times this comes up on commercials (whole frame divisible frame rates for frame cutting and ramping).

I'm hoping maybe for a 5K 16:9 mode (maybe at 4900 x 2600 or whatever the ratio is) basically enough vertical scan reduction to win back the extra 4 frames.

Can we make that a wishlist request?.......:)
Click to expand...


See my answer from earlier.
 
Thanks Deanan. Understood and that's what we do now. Of course sensor cropping in real terms means a lense change / moving the dolly / moving the set etc. So for a Director to run a pass at 100fps having been happy with a 25fps pass it's a big upheaval and something that is always complained about. Often when assessing the day I'm advising shooting at 4KHD for the whole shoot if they are wanting to switch framerates to 100 and back often. It's a shame to lose so much of what the camera is capable of.

The big advantage of Epic over Red is being able to stay on the same frame ratio without cropping. If there was a way to stay at a 5K frame (so your lens lengths match all day) and get 100fps (for the huge part of the world that shoots PAL) that would be a big advantage indeed.

When Alexa gets its 120fps bump and lens lengths match 35mm Viewfinders closely (prores 422 or otherwise) the 96fps will be one reason not to shoot Epic in Europe.

Just feedback from the frontline.....
 
Stacey Spears said:
#2. Steven Hilder previously posted this chart. Not sure it has ever been 100% confirmed by RED.

mysteriumx.png
Click to expand...

My original estimates were almost exactly the same as the specs that Jim quoted announced here. The chart you've posted is the one I re-did to match Jim's specs.

But that was a long time ago; I don't know for sure whether it matches the recording modes / pixel dimensions that ended up in Epic's firmware.
 
Thank's everyone for the input so far, it's been pretty helpful. I've been using the chart listed so thanks Steven for putting that together - I think that's as close as anyone is going to get unless RED release the details themselves.

I do still have a few questions below which I'm still unclear about, thanks for the help.

Firstly, we will be shooting 4k HD 16:9, so this is size for which I'm trying to calculate depth of field.

1. What is, or how do I accurately calculate the CoC? I have looked at the Zeiss forumla which suggests division of the format's diagonal length by either 1730, 1500 or 1000, but how do I decide which it is?

2. I learned that CoC changes depending on projected image, does the CoC created by the above formula work for a cinema sized image projection?


3. This question becomes redundant if I have the CoC but, does anyone know of a online DoF calculator that allows you to enter the image format dimensions? Sites such as DoF Master only have presets, or allow you to do it on CoC number and not custom image dimensions

Sorry to flog a dead horse, I'm just trying to get a crystal clear picture of how to correctly calculate Depth of Field with the Epic since I cannot find an easy to use calculator (which uses feet at least).

Thanks in advance.
 
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