Scarlet 2/3 Cinema 35mm Crop?

[rychoi]

Could I please get more information on the "crop factor" that the 2/3 Cinema Scarlet places upon 35mm lenses? I have been reading the forums constantly and saw a statement claiming that a 50mm prime is cropped to the equivalent of a 400mm. Is this statistic true?

I currently own a HPX170 attached to a Red Rock Micro system with 35mm Zeiss and Nikon Nikkor primes (Specifically an 85 and 50mm Zeiss and a 20mm Nikkor). I was planning on just using these lenses after purchasing the 2/3 Cinema, but if the crop is that drastic, wouldn't it be unrealistic to utilize a 2/3 Cinema with a 35mm mount?

This made me start thinking of purchasing the S35, but that + accessories may be out of my budget, and many of the features that come along with the S35 are not really essential towards my production objectives. Is it just a smarter buy to purchase the 2/3 Cinema and buy a set of 16mm lenses for it (Red Mini Primes?) or risk the crop factor of a 35mm mount?

I would greatly appreciate any information/advice. Thanks.

 

[David Rasberry]

For equivalent field of view, focal length for ff35 is about 3.8 times the focal length for 2/3" Scarlet. A 50mm on Scarlet would be about equal FOV to 190mm on ff35.

 

[rychoi]

Would you happen to know what the equivalent field of view would be to, not another Scarlet model, but rather the Red Rock Micro adaptor I already own?

 

[DAVID McNAMARA]

For equivalent field of view, focal length for ff35 is about 3.8 times the focal length for 2/3" Scarlet. A 50mm on Scarlet would be about equal FOV to 190mm on ff35.

What would the FOV be in super 35? I was under the impression the 2/3 scarlet was equivalent to super 16 in frame size.

 

[David Mullen ASC]

If the 2/3" Scarlet sensor is the same size as a 2/3" sensor in most video cameras, then that's 9.58mm wide. So the magnification factor between 2/3" and Super-35 (24mm wide) is 2.5X, and between 2/3" and FF35 (36mm wide) is 3.76X. Between Super-35 and FF35, it is 1.5X.

So basically to match FOV, for example, you'd use a 10mm lens on a 2/3" camera, a 25mm lens on a Super-35 camera, and a 37.6mm lens on a FF35 camera.

Or, again to match FOV, you'd use a 50mm lens on a 2/3" camera, a 125mm lens on a Super-35 camera, and a 188mm lens on a FF35 camera.

A Super-16 negative is 12.5mm wide. Regular 16mm is 10.3mm wide.

 

[Dan Hudgins]

Scarlet crop on Super16 lenses

Scarlet crop on Super16 lenses

You can see some sample Super16mm lenses on the Scarlet sensor area here, the increase in "telephoto" effect in the images, and the lower impression of sharpness. SLR lenses do not focus to better than 120lp/mm so it would be good to make a relay optic to shrink the image area using a field lens rather than a ground glass, that way their will not be a "crop factor" the SLR lenses would cover the frame with the same angle of view.

You would put about a 50 to 75mm 5megapixel lens on Scarlet, then focus into about a 35mm to 50mm field lens in the focal plane of your SLR lens, if you want to talk more about the details you can PM or email me... The 5megapixel lens would need extension tubes or a achromatic diopter lens to focus close enough to get the image on the field lens in sharp focus. The image size is adjusted by moving the SLR and field lens to and away from the 5megapixel lens, and the Vignetting is adjusted by moving the field lens to and from the SLR lens. You need a provision to change the fl of the field lens for SLR lenses that have their iris at longer or shorter distances from the focal plane, you can stack thin lenses to do that.

http://reduser.net/forum/showthread.php?t=28486&page=5

http://reduser.net/forum/showthread.php?p=402805#post402805

BTW, you would leave the iris open on the SLR lens, and use the iris on the 5megapixel (c mount) lens to adjust the DOF. To get full DOF the lens on the Scarlet should be f/0.7 but those are not 5megapixel so there is some compromise on how shallow the DOF can get with good resolution. You would focus with the SLR lens once the 5megapixel lens adjusted so that you get INF with the SLR lens set to INF. The image will be upsidedown unless you do flip in scarlet or turn it upsidedown.

 

[David Rasberry]

Here is an simple Excel spreadsheet that I constructed to approximate horizontal coverage angles based on focal length for some common film and digital formats. Enter lens focal length in the yellow box and see the results.

 

[Rick Presas]

I currently own a HPX170 attached to a Red Rock Micro system with 35mm Zeiss and Nikon Nikkor primes (Specifically an 85 and 50mm Zeiss and a 20mm Nikkor). I was planning on just using these lenses after purchasing the 2/3 Cinema, but if the crop is that drastic, wouldn't it be unrealistic to utilize a 2/3 Cinema with a 35mm mount?

oooh. i'd love to see some footage from this setup sometime!

That is basically the exact setup i will be getting if something doesnt work out with buying a scarlet.

 

[rychoi]

haha well, here is the most recent video i've filmed with the red rock setup (this is with an hvx200, not the 170): http://www.youtube.com/watch?v=7WTYwpRch8g

also, does anyone still have any info on the crop factor that a red rock M2 places on 35mm lenses in comparison to the scarlet 2/3 cinema?

 

[David Mullen ASC]

Doesn't the Redrock Micro use a FF35 groundglass (36mm x 24mm)? If so, it's that crop factor, which we've already mentioned.

 

[Scott C.]

You can see some sample Super16mm lenses on the Scarlet sensor area here, the increase in "telephoto" effect in the images, and the lower impression of sharpness. SLR lenses do not focus to better than 120lp/mm...

If you are shooting at 6k or 4k and shrinking it down for distro at 2k, then isn't your image going to end up plenty sharp without all of the optical gymnastics?

 

[David Rasberry]

We're talking about the 2/3" sensor 3k Scarlet, not S35 or ff35.

 

[Scott C.]

Gotcha David,

There it is rychoi, another argument for s35... since you are considering it.

 

[Dan Hudgins]

FL on the camera?

FL on the camera?

does anyone still have any info on the crop factor that a red rock M2 places on 35mm lenses in comparison to the scarlet 2/3 cinema?

Can't you zoom in and out through the DOF adapter to change the image size on the sensor?

If you use a fixed lens, then moving the adapter closer or farther away and refocusing should also change the crop a little, as would changing the focal length of the lens on the camera.

What is the width of the ground glass area in the red rock that the video camera sees?

If you use a field lens as I mentioned above, you can get no crop factor, you get the full width of the angle of view of the SLR lens, in fact since you are shooting 16:9 rather tha 3:2 you can get a little wider if you want.

 

[Dan Hudgins]

SLR lens lp/mm

SLR lens lp/mm

If you are shooting at 6k or 4k and shrinking it down for distro at 2k, then isn't your image going to end up plenty sharp without all of the optical gymnastics?

I was talking about using the SLR lens direct on the sensor vs. through relay optics.

If the SLR lens can resolve like 35lp/mm wide open than using it direct will give soft results on the 2/3" sensor, and somewhat soft results on the S35 size sensor.

Good S35 lenses resolve 50 to 80lp/mm and good 2/3" lenses resolve 120 to 150lp/mm

If you reduce the FF35 size image by a factor of almost 4 you get that 35lp/mm increasing to over 120lp/mm which would look better than going direct if the relay optics are good enough not to loose much.

Going onto a ground glass causes some flare and reduced resolution, OK for a camcorder lens and sensor maybe, but you can probably do better with clear optics for REDCODE recording at 3K.

"Plenty sharp" is a subjective value, as sharp as you can get is something some would hope for? What does the pixel count have to do with the lens resolution? Its the relationship of the vertical lines of resolution per frame height of the lens that cary over to the end viewer so long as the pixel count is high enough to support the lens's resolution. What is "plenty sharp" on the frames recorded for someone in the front row of an IMAX theatre would not be the same per frame height as for making a letter boxed DVD, etc. Putting a soft lens on a 6K camera gives you a very large file for a 1k true resolution image, adding pixels does not add resolution much above what the lens can resolve with high MTF?

 

[John Goodbrad]

Hey Guys, I was trying to put together a chart that compares a few different size image sensors with what lenses to use. This is what I came up with...

If the FOV is the same for:

4mm on 2/3"
10mm on s35
15mm on ff35

then each lens should just barely cover the sensor on each. (No Vignetting)

This information would come in handy when you are shooting 2k on a ff35 / s35 at high frame rates. The 2k will be slightly windowed from 3k, but at 3k you could throw on a 4mm b4 mount lens and shoot the same FOV as you would a 15mm on the ff35 for a wide angle shot.

In essence, since the sensor would be windowed anyways.... wouldnt it be best to shoot a super wide on a b4 mount if you are looking for a wide angle at high frame rates / 2k?

Does this information look correct?

The widest Red mini prime will be 6.5mm which should equal approximately 24.44 on the ff35 sensor. That would probably be wide enough as well.

 

[David Rasberry]

I don't think 2/3" Scarlet will shoot 2k windowed, it is not in the spec. The S35 And FF35 models shoot 2k windowed, but due to the larger pixels this is slightly larger than 2/3" size, a little over 11mm wide for S35. For HD finish, 2k allows use of S16mm/HD video format lenses on the larger sensors, smaller and lighter than 35 format lenses,especially the zooms. These are the lenses 2/3" Scarlet will use anyway, so no advantage to cropping to 2k.
For the Scarlet line, shooting 2k is also the only way to get high framerates on S355/ff35. But this also doesn't apply to 2/3" Scarlet. Even the high speed frame rates are shot at 3k.