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  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

What's the crop factor for shooting 2K on EPIC?

Here's my long answer to a similar question:

Full-Frame 35mm, such as on the Canon 5D, means a 36mm x 24mm sensor. It may be easier if you just compare horizontal view rather than diagonal view since then you don't have to deal with aspect ratio affecting the diagonal length.

"Super-35" is technically 24mm wide -- which is what the Red One is in 4.5K mode. So that's a 1.5X difference with FF35 (36 divided by 24 = 1.5.)

Various widths:
36mm = FF35 / Canon 5D sensor
30mm = entire M-X sensor
27.65mm = 5.1K area of M-X sensor (Epic 5K mode)
24.4mm = 4.5K area of M-X sensor
24mm = Super-35 film
22.3mm = Canon 7D sensor (APS-C)
22.12mm = 4K area of M-X sensor
16.59mm = 3K area of M-X sensor
11.06mm = 2K area of M-X sensor

I got these figures off of the internet so some may be off a tiny bit, but they are all close enough for you to calculate the difference in field of view. Just keep in mind that there is a whole other issue of vignetting when you put a lens designed to cover a smaller sensor onto a larger sensor. But that doesn't affect focal length calculations for field of view.

The short answer is that there is a 1.25X difference in size between 4K on the Red One and 5K on the Epic. So your 18mm, assuming it doesn't vignette is going to look more wide-angle on the Epic in 5K mode than it does on the Red One in 4K mode -- it will look like you were still shooting in 4K but had switched from an 18mm to a 14.5mm in terms of the increase in field of view. But remember, you didn't change focal length, just view... I'm only talking about what you'd have to switch to on the 4K camera to match the view of the 18mm on the 5K camera. Or, if you liked the view of the 18mm on the 4K camera, you'd have to switch to a 22.5mm lens on the 5K camera to maintain the same field of view.
Click to expand...

However the short answer is that if you switch from 5K to 2K, that's a 2.5X size difference -- just divide 5 by 2!. "Crop factor" depends on what you are comparing to what else. Most people, for some reason, use FF35 as their basis of comparison for focal lengths, though that implies most people shoot FF35 regularly and are thus most familiar with that field of view for those focal lengths, and I'm not sure that's true anymore, that more people shoot FF35 cameras than any other kind.
 
APS-C / NikonDX is the most commonly shot frame size for "35mm" photography. Period. People have not been predominantly shooting FF35 since digital took over the SLR market. I also find it curious that people want to relate crop factors to FF35... Why? Especially considering so many people are actually NOT familiar with it. Even camera makers do it, which also baffles me, because it really has no logical basis, even as a common frame of reference. It only makes sense to a handful of old coots that have been shooting FF35 for the past 45 years and are now taking a foray into digital.

What people really should concern themselves with is Angle Of View and what AOV is provided by a given focal length on a given imager format. But I think they don't because AOV calcs are kinda hard to do in one's head and a great many people, sadly, struggle with the "math" behind relational crop factors. I see so many improperly applied and referenced crop factors out there, it's pathetic. And these people call themselves "photographers". It's as bad as "carpenters" who can't figure out which angle to cut the ends of two boards to make a symmetrical miter joint. Yeah, I've met a few of those too...
 
Michael Kromschroeder said:
Thanks guys, so compared to an Alexa I have 2x crop factor on the lens when using 2 k on EPIC?
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More or less. To be more precise, picture area on the Alexa sensor is 23.76mm wide versus 11.06mm wide for the Red One in 2K mode, so that's a 2.15X difference.
 
Please correct me if I'm wrong. Isn't most people refer FF35 to 35mm film. Since they have approx the same size ?
 
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