Scarlet 2/3" and Nikon Still Lenses...

[David Mullen ASC]

You obviously have no clue what I'm asking so just never mind.

I guess I'm trying to teach you to ask a question more accurately and clearly so the answers would be more accurate and clear.

Confusing questions don't lead to clear answers. You asked if there would be any cropping with the Mini-Primes. You asked if the crop factor would affect the Mini-Primes, you asked if they would be designed to compensate for the crop factor. All those questions don't quite make sense.

 

[Dan Hudgins]

Pin-hole

Pin-hole

The sensor crops the circular image of the lens to the rectangle shaped frame we see when watching a film...

The first "cameras" were made with a pin-hole in the wall of a dark room, on the other wall was an upsidedown image of what was outside in the sunlight.

All lenses are like a pin-hole except that the use of curved glass on each side of the pin-hole lets the opening be enlarged so that more light can pass without the image points also geting larger for the subjects in the plane of focus.

Since all lenses are like a pin-hole, for all lenses of the same focal length, the distance from the image plane to the "pin-hole" distance, make images of about the same size, the larger the focal distance the larger the image.

Just because a SLR lens makes a image circle larger than the sensor does not mean that that image will be sharp enough to be usable for feature film production.

Most lens are made to resolve between 1/300 to 1/1200 the diameter of the image circle. So if a SLR lens makes a 45mm image circle and a mini-prime makes a 12mm image circle you would expect that the mini-prime would resolve image spots 12/45 smaller or about 3x to 4x as sharp.

Looking the other way around, say the mini-prime gets you 800 video lines resolution on the 2/3" sensor, then if the Nikon SLR lens is making a spot 3x to 4x as large you would get 800*(.333) to 800*(.25) video lines, or about 266 to 200 video lines at 80% MTF.

It does not make much sence to me to purchase a $7000 3K camera setup to get sub-SD results?

If you want to use SLR lenses purchase the FF sensor SCARLET, it may be lower cost since the lenses good enough to resolve 3K on the 2/3" camera will cost more than used SLR lenses and that will offset most or all of the extra cost of the FF brain if you are going to have a set of full focal lengths.

About the focal length issue, you find the ratio of the widths of the sensors to figure the focal length to use for each sensor size,

Wide angle: 2/3" 6mm-12mm, S35 18mm-28mm, FF 28mm-35mm

Normal: 2/3" 16mm-20mm, S35 40mm-50mm, FF 60mm-85mm

Telephoto: 2/3" 35mm-50mm, S35 75mm-85mm, FF 100mm-150mm

The normal for 2/3" is not 25mm like for 16mm film because 2/3" sensor is smaller and the format is 16:9 so you need lenses a little wider because of the smaller frame height. Just the way you need to use wider lenses for Techniscope even though the frame is the same width as normal 35mm, the frame height is lower so you use a 35mm or 28mm as your normal lens, not a 50mm which was normal for silent full frame height.

Because the resolution is also in ratio to the total focal length the shorter focal lengths tend to be a little sharper in the center of the frame, but may be lower in the corners depending on the quality of the make. So a 12mm for 2/3" will be a little higher resolution than a 50mm for any format in the center of the frame in general.

If you use a DOF adapter, you can get sharp results on a 2/3" sensor using Nikon SLR lenses since the relay optics in the DOF adapter can reduce the large FF image circle to the smaller 11mm image circle used by the 2/3" sensor, but those relay optics would need to resolve at least 200lp/mm at the 2/3" side, and the other parts of the DOF adapter like the field lens would need to be of high quality, and the relay optics would limit the maximum f/ stop and light transfer. With a well desigined DOF-relay optics system you could get by will less that a stop loss with a f/1.2 Nikon SLR lens in front, but most things you can buy will probably have larger light losses.

In all cases the image circle the lens makes must be larger than the sensor size. You can get a 12mm Nikon FF SLR lens and put it into a mount adapter for C mount Scarlet, but the image will not look like a 200lp/mm 12mm lens made for 2/3" sensor cameras. I have done tests with M42 FF SLR lenses using an SD 2/3" camera, and even at SD you can see the SLR lenses are not as crisp as megapixel 2/3" machine vision lenses for the most part, even if you stop down to f/5.6 you may still get CA from the SLR lenses that can be gross.

I am sure the Scarlet with the built in Zoom will be good for what is was ment to be, but if you want to use FF SLR lenses, you may come out way ahead to just get the FF brain in the first place, since even the S35 brain will give about 30% less resolution using the FF lenses beause those lenses are made for a larger image circle (although the corners of the frame may show more CA on the FF sensor than the S35 sensor because the S35 will crop just the center of the FF lens image circle).

 

[Jeff Kilgroe]

You obviously have no clue what I'm asking so just never mind.

I would've answered your question the same way that David did. Or another way to answer is that. There is no compensation for crop factor with the mini primes. They just are what they are... And that is their respective focal lengths and they work the same as any other 6, 8, 16, 25, 50 mm primes do and they have an image circle at least good enough to cover the 2/3" sensor. These are common focal lengths for 2/3" imager sizes.

Dan also talks about resolving power of a lens. I'm expecting the mini primes to be wicked-sharp in order to resolve that high-density 2/3" sensor. There's a very good chance that the mini-primes are sharper than the RPP's and other "sharp" S35 glass out there. As often lenses designed for HD cameras and 16mm film cameras can be.

Dan also makes a real good point with his last statement. And it's a point I and a few others have brought up in the Scarlet threads before. 35mm adapters really don't make a whole lot of sense here if someone is primarily going to use S35 or FF35 lenses. By the time you buy the 2/3" interchangeable brain and a good 35mm adapter, you may as well just buy the Scarlet S35 brain with the mount of your choice. Eventually there should also be the FF35 Scarlet brain, but I would say it's close to 2 years away at this point (just a guess).

 

[Daniel Browning]

You obviously have no clue what I'm asking so just never mind.

There's nothing wrong being ignorant of some aspects of sensor size. Nor with asking nonsensical questions that betray such ignorance. But to respond to David's excellent answers in the manner of a fool is a mistake.

 

[Zul Y]

I don't know -- there are some theories that all the unused area of the glass of a lens meant for a larger sensor will lower the contrast, but the truth is that some of the still lenses are just naturally less contrasty than some cine lenses by design. A bigger issue is just that a good lens designed specifically for a 2/3" sensor has to have a higher MTF, whereas a lens designed for a large sensor doesn't necessarily have to have resolve as many lines per millimeter when you have more overall millimeters to capture the subject with. But that's only in theory, in reality, a still camera lens may or may not be as sharp as a 2/3" lens depending on a number of factors.

Yea, I read about it before and have been trying to wrap my head around all that theory but I guess it's all a matter of how a lens would perform in real world scenarios.
I mean if the image produced by the lens works for you then it works for you!

Anyone remembered a frame grab of Jim's lizard shot with the 100mm RPP on the scarlet 2/3" sensor?
Of course the 100mm RPP is far superior than an old manual still lens but that image works for me.

 

[David Rasberry]

The RPP's are sharper than most 35mm still lenses except the very top line models and are optimized for digital sensors, as opposed to film.

2/3" image width, in 4:3 is virtually identical to 16mm 4:3 TV projection aperture, so a given focal length would produce the same FOV as a 16mm transfer. It is about the same width in 16:9 as a crop of standard 16mm, but narrower than super 16mm. Scarlet's 3k 1.89:1 cinema ratio image area is slightly wider than 16mm film projection aperture and also slightly wider than the standard 9.6mm reference width for 2/3" HD. Note: This is based on the previously announced 3.2 micron pixel size sensor with dimensions of 10.1mm x 5.35mm and maximum active image area of 3072x1620 pixels for the 1.89:1 ratio or 2880x1620 for HD 16:9. Interestingly enough, 2880 x1620 is also the resolution of the ARRI D21 sensor. ARRI deBayers and scales to 1080p HD in camera for final image output.