actual 2/3" specs for DoF calculations

[Zach Tucker]

this may sound like a repeat post but it actually differs from the other sensor size DoF threads.

Anyone know what the *usable* size of the 2/3" scarlet sensor will be? yes, there will be speculation but maybe it will be relative to the usable size of the current red one sensor ( some percentage? ). meaning, if the 2/3" sensor is 10.1mm x 5.35mm (and thus a diagonal of 11.4mm by my calculations) then is 100% of that sensor used to capture an image? (let's ignore aspect ratios for now and just stick with full horizontal specs)

the reason i ask is that clearly this old glass tube thirds-of-an-inch sensor size hoo-ha is a total generalization. 2/3" on one camera is not the same as 2/3" on another. and even if the chip sizes were the same on two different 2/3" cameras their actual usable area may differ.

ultimately i'm trying to find DoF specs on the 2/3" scarlet. let's take a given FOV achieved with a 75mm lens on an S35 scarlet at say, f4.0. to get a similar FOV on a 2/3" scarlet (given current list of mini-red primes) i'd likely use a 25mm T1.8. so, cool, i've matched FOV, now what happens with my DoF? if i shoot the 2/3" scarlet with 25mm lens set to f2.0, what would my DoF be like now that i'm open 2 more stops than on the S35 75mm at f4?

in using various DoF calculators i'm finding a wicked discrepancy. almost all the calculators have presets. "full frame 35mm" "canon 5d" "2/3 sensor", etc. well, on two different calculators (when using the 2/3" sensor preset for film back) they can differ as much as 200% ... soooo that's whack. i guess it's understandable given the inaccurate legacy thirds-of-an-inch sensor specs.

so, in the end:

1) guesses on usable horizontal size of the 2/3" 10.1mm sensor?

2) anyone know of a DoF calculator that i can put my own sensor specs into?

.z

 

[David Mullen ASC]

The camera doesn't exist yet so how can we know the actual area used for recording? Of course we're speculating -- what else can we do?

Once you match FOV by switching focal length, the effective DOF difference between 2/3" and S35 is about 2.5-stops. This will probably be true for the 2/3" Scarlet compared to the S35 Scarlet. Sure, the exact amount may differ a little from that, but I'm not sure why you need to be any more precise than that, what the practical purpose would be.

So technically you'd use around a 30mm lens on the 2/3" camera to match the FOV of the 75mm lens on the S35 camera, and you'd have to open up the 30mm lens by 2.5-stops to match DOF of the 75mm lens on the S35 camera.

 

[David Rasberry]

Guesstimate based on the announced pixel size of .0032 x 3072 H = 9.83mm for 2k widescreen. .0032x2880= 9.21 approx. for 16:9 .0032x1620 = 5.18V

Angenieux lists 9.6x5.4 for 2/3" 16:9 angle of view specs for their HD lenses.

I threw together a simple spreadsheet table for approximate angle of view calculations for different size sensors vs focal length. If anyone is interested I can post it if I can find it.

 

[Zach Tucker]

Once you match FOV by switching focal length, the effective DOF difference between 2/3" and S35 is about 2.5-stops. This will probably be true for the 2/3" Scarlet compared to the S35 Scarlet. Sure, the exact amount may differ a little from that, but I'm not sure why you need to be any more precise than that, what the practical purpose would be.

It's all speculation for sure, but that is certainly close enough. That makes more sense to me than these DoF calculators being so different from each other given I provided them with the same parameters.

Thanks!

 

[David Mullen ASC]

Angenieux lists 9.6x5.4 for 2/3" 16:9 angle of view specs for their HD lenses.

Which matches the 2.5X figure (9.6mm for 2/3" versus 24mm for S35).

 

[jonathan homer vargas]

QUESTIONS FOR RED

SUMMER THAT WE WILL HAPPEN WITH THE SCARLET?

Is in production?


PLEASE JIM