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Super 35 crop Factor on Scarlet 2/3", sooooo confusing!

Andrew Rieger

Andrew Rieger

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Alright, I figure that the lens thread would be the best place to ask these questions. Here it goes...

So I have decided to purchase a Scarlet 2/3" and I am looking into the lens options available to me. There are the Red miniprimes but I am still waiting to see the optical performance and and the possibility of using a standard follow focus so for now, they are out.

Second, where I live, Super 16 glass is pretty hard to come by with limited choices and from what i hear, may not resolve the 3K sensors.

Super 35 lenses are much more abundant and have a greater selection. The problem is, I am finding the discussion on field of view, crop factor and depth of field changes when using Super 35 lenses on a a 2/3" sensor, to be very, very , very confusing.

Yes, I have heard the phrase, "a 50 is a 50 is a 50"

For this example I will be using a six lens set of Zeiss-Arri Ultra Primes (16, 24, 32, 50, 85 and 135mm to be precise)

I know that a Super 16 50mm lens will have the same fov as a Super 35 50mm lens but things get interesting when you place the S35 lens on the S16 cam.

According to other posts, the crop factor of S35 cine lenses on the 2/3" sensor is 2.47. Thus, when using a S35 lens on a 2/3" chip:

S35 16mm= 2/3" 39mm
S35 24mm= 2/3" 59mm
S35 32mm= 2/3" 79mm
S35 50mm= 2/3" 123mm
S35 85mm= 2/3" 209mm
S35 135mm=2/3" 333mm

I am not saying that the lens turns into another lens (everyone gets upset and corrects you when you say that a 50mm S35 lens turns into a 123mm lens), I am just saying that the field of view changes.

Lets just say that I am using the 85mm lens on a RED One, I then switch to the Scarlet 2/3" from the same distance to the subject. I want the same field of view that the RED One had so I then put the 32mm Super 35 lens on the Scarlet, resulting in a 79mm fov which is not the same but very close. Is this the correct way to do things?

Finally, despite the "a 50 is a 50 is a 50 thing", isn't it true that in the example above, the 32mm S35 lens will have a shallower depth of field than say, an 85mm Super 16 lens at the same t stop? I seem to recall that crop factor also changes the DOF characteristics of lenses, similar to how many people make the depth of field more shallow on prosumer small chip cams by backing way up and then zooming way in.

If my understanding is correct, then when using a 2/3" chip, a Super35 32mm T 1.3 will produce a more shallow DOF than a Super16 85mm T 1.3 lens, despite the fact that the field of view is very similar.

Wow, that was a mouthful. I'm just a beginner trying to gain understanding. You have to start somewhere.
 
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The reason we say that a "50 is a 50 is a 50" is because people start to confuse themselves when they only want to think about lenses in terms of conversion factors rather than simply learning what field of view different focal lengths give you on different formats.

In other words, if you take a 50mm lens off of a 35mm camera and put it on a 2/3" camera, it's still a 50mm lens, it just has a narrower view. It doesn't become some other focal length.

It's simpler to just think of the series of focal lengths you will be using as containing your wide to telephoto range. So you learn what your 8mm gives you versus your 28mm, etc. on your specific camera -- you don't have to make conversions to some format you aren't even shooting.

Of course, you may make conversions at first to know what lens to rent or buy, but honestly, it's not complicated. It's a 2.5X crop factor between Super-35 and 2/3", and remember that the typical range of focal lengths always get shorter for smaller formats to equal the same range of views of longer lenses on larger formats.

So you'd use a 20mm lens on a 2/3" camera when you wanted the same field of view as a 50mm lens on a Super-35 camera.

Let's say that your typical range used in Super-35 moviemaking is often 18mm to 100mm (and there's a Cooke zoom in that range.) Well, you'd need a 7.2mm to 40mm range on a 2/3" camera to get that same range of views.

So right off the bat, you just have to realize that your 6mm, 7mm, 8mm, 9mm lenses are wide-angles in 2/3", the 12mm, 16mm, 20mm lenses are the middle focal lengths, and beyond that start to become your telephoto lenses.

So where exactly is the confusion coming from?
 
Andrew Rieger said:
For this example I will be using a six lens set of Zeiss-Arri Ultra Primes (16, 24, 32, 50, 85 and 135mm to be precise)

I know that a Super 16 50mm lens will have the same fov as a Super 35 50mm lens but things get interesting when you place the S35 lens on the S16 cam.

According to other posts, the crop factor of S35 cine lenses on the 2/3" sensor is 2.47. Thus, when using a S35 lens on a 2/3" chip:

S35 16mm= 2/3" 39mm
S35 24mm= 2/3" 59mm
S35 32mm= 2/3" 79mm
S35 50mm= 2/3" 123mm
S35 85mm= 2/3" 209mm
S35 135mm=2/3" 333mm
Click to expand...

Even I find your list confusing, but if you're trying to figure out the equivalent lenses to obtain the same field of view using a 2.5X crop factor, it would be:
S35 16mm = 6.4mm in 2/3"
S35 24mm = 9.6mm in 2/3"
S35 32mm = 12.8mm in 2/3"
S35 50mm = 20mm in 2/3"
S35 85mm = 34mm in 2/3"
S35 135mm = 54mm in 2/3"

But if you're asking how much more telephoto your S35 lenses will behave on a 2/3" camera, then your figures are about right. Just as long as you understand that your S35 lenses don't actually change into those longer focal lengths on a 2/3" camera, they just behave like those focal lengths would on a S35 camera.
 
If my understanding is correct, then when using a 2/3" chip, a Super35 32mm T 1.3 will produce a more shallow DOF than a Super16 85mm T 1.3 lens, despite the fact that the field of view is very similar.
Click to expand...

The equivalent in view of a 32mm lens on a Super-35 camera is a 12.8mm lens on a 2/3" camera. If both are shot at f/1.3, at the same distance, the 12.8mm lens image on the 2/3" camera will have more depth of field. Not sure why you'd compare a 32mm lens on a Super-35 camera to an 85mm lens on a Super-16 camera, that's sort of apples and oranges in terms of view, you'd be comparing a wide-angle image to a telephoto image -- the field of view is not similar at all. You're getting confused because the 32mm lens switched from the S35 camera to the Super-16 camera would behave more like a telephoto lens, have a narrower view as if you were shooting with an 85mm lens on the Super-35 camera. In other words, you have it backwards -- if you wanted to match view, you'd put the 85mm lens on the Super-35 camera and the 32mm lens on the Super-16 camera, not the other way around.
 
Crop factors are the devil. I all too often see them calculated and/or referenced incorrectly, even by professional shooters who should know better. They lead to all sorts of confusion and problems. Too many people thinking that crop factors relate to lenses, when in fact the crop factor is only a frame of reference when relating two different imager (sensor) sizes. Many like to assume a reference point of FF35, which also further confuses things on these forums since many here are not FF35 stills shooters to begin with. If someone asks you what the crop factor is for a certain lens, you should say "there is no crop factor, but this lens is designed to cover XXXX image area or size". If someone asks you what the crop factor is of a certain sensor or camera body, you should ask "In relation to what?".

Focal length is focal length, just as David Mullen explains. I've said it many times here on the forums that the best way to look at all this, especially because all these new cameras will offer a multitude of recording formats and lens options, is to make a chart. A grid to reference focal length and FOV (or Angle of View, AOV to be more appropriate) at certain common imager sizes. ...And yet no one ever seems to actually do this. So I guess I'll go ahead and make one and post it here shortly; over the next few days. In addition to this, a chart of various lenses and their area of coverage would be great to have. Matt Duclos is building such a thing. Sorry, don't have the link handy and I'm too lazy to search at the moment.

There is a very common misconception out there that a 50mm FF35 lens is different than a 50mm S35 lens, which is also different than a 50mm 2/3" or S16 lens, etc.. When in reality, a 50mm focal length is always a 50mm focal length. It is only the FOV that changes because your recorded image area changes in size. Of course, a 50mm lens designed to cover FF35 will differ in that regard, coverage, compared to a 50mm lens designed to cover a 2/3" sensor. But if you put a 50mm lens that is designed for a 2/3" camera onto a 2/3" camera and take a picture, then replace that lens with a 50mm lens designed to cover an FF35 sensor onto that same camera to take a picture, you will get the exact same picture. Of course, optical characteristics such as image geometry, flaring, color rendition, etc.. between the two may differ due to different lens designs, but the FOV / AOV will be the same.
 
Wow, thanks so much for the help Mr. Mullen! I'm getting cinematography advice from an ASC member, not many aspiring filmmakers can say that. I am a huge fan of your work and am constantly impressed by the caliber of filmmakers that frequent this site.

I am self taught but I am looking at studying film production in grad school in my home state of California after my undergrad studies here in Texas end. Most of my peers interested in a career in film want to be directors but I really want to be a cinematographer. My dad was an automotive photographer and a film historian so I have been raised with a love of both arts.

On to the lens issue. I think that I was confused because it seems that there is so much misinformation on the internet about this stuff. I am glad that you have cleared up the confusion.

I believe I understand what you are saying. As an example, I have an Arri 35 and a Scarlet 2/3 side by side shooting the same subject an equal distance away. I am using a S35 32mm Zeiss prime on the Arri cam. I want the same field of view with the Scarlet that I have with the Arri. Thus (still using S35 glass), I would use a 16mm S35 prime to get a similar field of view out of the Scarlet. Correct?

I would be able to avoid all these problems by using Super 16 glass but in San Antonio, Super35 glass is much more available.

I believe I understand the DOF question as well now. Yes, I was using the 32mm S35 lens as a telephoto on the 2/3 sensor. My question was, if I were to compare the 32mm S35 lens on the 2/3 chip to say, a 34mm Super 16 lens (both at T 1.3), which would have a shallower depth of field? They would be the same correct?

I don't know why I said an 85mm S16 lens in my first post. My example got so complicated, I confused myself.

I guess in a nutshell, I am trying to find out if I can get a good focal length range out of a set of S35 primes, while using the Scarlet 2/3. This really is not that confusing its just I am new to all this so everything is confusing to me. I am coming from 35mm mini dv adapters using my father's still Nikon lenses and I had no idea what crop factor was until I started researching other formats a couple of years back. Your responses have been been very helpful. Thank you.
 
Thanks Jeff. Your response came in as I was writing to Mr. Mullen.
 
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Andrew Rieger said:
I believe I understand what you are saying. As an example, I have an Arri 35 and a Scarlet 2/3 side by side shooting the same subject an equal distance away. I am using a S35 32mm Zeiss prime on the Arri cam. I want the same field of view with the Scarlet that I have with the Arri. Thus (still using S35 glass), I would use a 16mm S35 prime to get a similar field of view out of the Scarlet. Correct?
Click to expand...

Well, technically you'd use a 12.8mm if there were such a thing...

I believe I understand the DOF question as well now. Yes, I was using the 32mm S35 lens as a telephoto on the 2/3 sensor. My question was, if I were to compare the 32mm S35 lens on the 2/3 chip to say, a 34mm Super 16 lens (both at T 1.3), which would have a shallower depth of field? They would be the same correct?
Click to expand...

If you're asking if a 32mm lens is similar to a 34mm lens, I'd say yes. The only reason it makes a difference whether it was made for a Super-35 or a Super-16 camera is coverage, the size of the projected image coming out of the back of the lens -- the lens made for the smaller format would probably vignette on a larger format.

I guess in a nutshell, I am trying to find out if I can get a good focal length range out of a set of S35 primes, while using the Scarlet 2/3.
Click to expand...

To put it in a nutshell, you have to find some really short focal lengths if you want wider-angle shots. You know, Zeiss and Cooke both made some shorter focal lengths for their Ultra Primes (Zeiss) and S4's (Cooke) specifically for the Super-16 market, which allowed them to make the lenses a bit smaller physically than if they had to cover the Super-35 frame. The idea was that even if you were shooting in Super-16, you'd get a normal set of Super-35 lenses and add these short focal lengths made for the Super-16 market.

Often a Super-35 lens set begins at 18mm, maybe 16mm at the widest, so you'd want to augment that set with some Super-16 primes starting in the 6mm to 12mm range to get wide-angle shots.
 
Thanks so much. Everything seems so clear now.

I have seriously gained an invaluable amount of knowledge since I became a member.

My friends always ask me, "Why are you never on facebook?" Probably because I am always on Reduser ;)
 
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That is one hell of an expensive lens! Rather larger than you really want for a 2/3 inch camera. It's not very fast as it was designed to cover 35mm film. You would do much better with modern S16 lenses from Zeiss or Cooke.
 
Andrew Rieger said:
I guess in a nutshell, I am trying to find out if I can get a good focal length range out of a set of S35 primes, while using the Scarlet 2/3. This really is not that confusing its just I am new to all this so everything is confusing to me. I am coming from 35mm mini dv adapters using my father's still Nikon lenses and I had no idea what crop factor was until I started researching other formats a couple of years back. Your responses have been been very helpful. Thank you.
Click to expand...

If you are set on the 2/3" Scarlet and wish to use primes, I think a set of the RED mini primes will be an outstanding value. And they are all good focal lengths for use with the 2/3", 6mm up through 50mm. If their optical performance is close to that of the Red Pro Primes, they will be excellent. As for use with a follow focus, I don't see what everyone is so concerned about. They don't look much different than other current small primes designed to cover 2/3" or 16mm. I would think an Arri FF-5 or LFF-1 would be good choices for FF units. But they should also work just fine with the FF-3, FF-4, possibly the MFF-1...

If you are trying to make existing lenses work, such as SLR still lenses, etc.. or PL mount cine glass designed to cover S35, then it will be hard to cover that wide end. There's not much out there in S35 land that is wider than 18mm or so and the little bit that is gets very expensive. If you want something in the 5~8mm range, you are looking at huge money or compromising and going to a fisheye or something else. All to do with the coverage of a lens.

S16 PL mount lenses can be a good bargain. You can pick up older zooms for relatively little money and get something that's around 9mm or so on the wide end. But do keep in mind that 2/3" is still smaller than S16 and a real wide angle lens on 2/3" would be a 5mm up to maybe 7mm. Most S16 lenses don't get much wider than 8mm. The 16mm ILLUMINA primes are also an excellent value, designed to cover S16 and they range from 8mm to 50mm at T1.2.

Andrew Rieger said:
Knowing what I know now, I think I would add a lens like this to the prime set in order to have something on the wider end.

Zeiss 8mm T 2.8
Click to expand...

OMG NO!!!!! That lens is actually quite amazing in its own way -- it's a rectilinear 8mm designed to cover Super35. It does exhibit some distortion due to its rectilinear nature. It's a specialty lens, not a general use wide angle. And like Stephen points out, it's very expensive. These sell on the used market for over $25K, if you can find one.
 
I am talking about renting the Zeiss, I could never afford a cine lens, in any focal length. The RED miniprimes would be about all I could actually afford to own, everything else would be a rental item.
 
Standard 16mm lenses will cover Scarlet 2/3" just fine too. Good used ones are significantly less expensive than S16 glass. The Switar series made for Bolex (not the RX versions though) are excellent, Schneider and Zeiss lenses made for Arri 16mm cams are excellent too. But the Red mini-primes are the best value if it is primes you are after. They are optically matched to the sensor.
 
Jeff Kilgroe said:
Crop factors are the devil. I all too often see them calculated and/or referenced incorrectly, even by professional shooters who should know better. They lead to all sorts of confusion and problems. Too many people thinking that crop factors relate to lenses, when in fact the crop factor is only a frame of reference when relating two different imager (sensor) sizes. Many like to assume a reference point of FF35, which also further confuses things on these forums since many here are not FF35 stills shooters to begin with. If someone asks you what the crop factor is for a certain lens, you should say "there is no crop factor, but this lens is designed to cover XXXX image area or size". If someone asks you what the crop factor is of a certain sensor or camera body, you should ask "In relation to what?".

Focal length is focal length, just as David Mullen explains. I've said it many times here on the forums that the best way to look at all this, especially because all these new cameras will offer a multitude of recording formats and lens options, is to make a chart. A grid to reference focal length and FOV (or Angle of View, AOV to be more appropriate) at certain common imager sizes. ...And yet no one ever seems to actually do this. So I guess I'll go ahead and make one and post it here shortly; over the next few days. In addition to this, a chart of various lenses and their area of coverage would be great to have. Matt Duclos is building such a thing. Sorry, don't have the link handy and I'm too lazy to search at the moment.

There is a very common misconception out there that a 50mm FF35 lens is different than a 50mm S35 lens, which is also different than a 50mm 2/3" or S16 lens, etc.. When in reality, a 50mm focal length is always a 50mm focal length. It is only the FOV that changes because your recorded image area changes in size. Of course, a 50mm lens designed to cover FF35 will differ in that regard, coverage, compared to a 50mm lens designed to cover a 2/3" sensor. But if you put a 50mm lens that is designed for a 2/3" camera onto a 2/3" camera and take a picture, then replace that lens with a 50mm lens designed to cover an FF35 sensor onto that same camera to take a picture, you will get the exact same picture. Of course, optical characteristics such as image geometry, flaring, color rendition, etc.. between the two may differ due to different lens designs, but the FOV / AOV will be the same.
Click to expand...

That is correct, but a little hard to follow.

The angle of view of a lens is calculated using the following formula:
2 x tan-1( l / (2 x f) )
where ' l ' is the length of the frame in the direction that you want the reading and ' f ' is the focal length of the lens.
As the different sensors have slightly different aspect ratios, the "35mm equivalent lens" is calculated using the diagonal measurement of the current sensor against that of 35mm film.

Also remember that lenses can generally be used on sensors with a smaller diagonal measurement than the sensor (or film) they were designed for (although causing "cropping" aka magnification). But a lens will not cover the area of a sensor that is larger than what that lens was designed for. You can use a 35 mm film lens on a 2/3"chip. But you can't use a 2/3" ENG lens on a 35mm sensor.
 
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