16mm vs. 35mm labeling issue

Adam Nikolaidis · February 17, 2005

I've been reading the forums for a while now, but this is my first time posting. I tried searching for this, but didn't seem to come up with anything useful.

I'm aware that, for example, a lens length of 25mm is 25mm, whether or not it's on a 16mm camera or a 35mm camera (though the FOV is clearly different). I'm wondering, however, if manufacturers have ever "compensated" for the difference in FOV between these negative sizes by mislabeling the length? E.G., are there any lenses out there labeled for use with 16mm cameras that have a true length of 25mm but are labeled "50mm"?

I don't think this is the case, but a representative from a (in my understanding reasonably reputable) used equipment vendor seemed to indicate that he thought a specific 25-250mm 35 lens would look like 50-500mm, but implied that a 15-150mm Super16 lens would not suffer the same relative change in FOV to 30-300mm (for a 16mm camera). It could be that I'm misreading his email, but I wanted to make sure I'm not totally off base in assuming that the 15-150 and 25-250 would both have the same relative difference in FOV when used with a (Super)16mm camera.

Is this another case of seeming misinformation? Is he on crack? Am I?

Reading this over, I hesitate to even bother asking because it seems so obvious to me. A response of "Adam, you are not on crack" would be clear enough.

Thanks,

Adam

Edited February 17, 2005 by Adam Nikolaidis

Michael Nash · February 17, 2005

I'm not sure who's on crack here, maybe it's me, because I couldn't quite understand your middle paragraph.

I think you've got it right, a 25mm is a 25mm lens; hence a 15-150 is a 15-150 and a 25-250 is a 25-250 no matter what camera it's on. The field of view changes between formats, regardless of what lens gets swapped between them. There's no way the field of view changes between film formats with one lens but not another.

And anyone who labels a 25mm lens a 50mm when they put it on a 16mm cameras IS on crack! :P

There's no need to get all confused about this issue. Focal length is focal length. Period.

Rik Andino · February 17, 2005

Adam you're not on crack.

No one labels a 25mm lens 50mm for S16...unless they're on crack.

If you know more than a vendor don't listen to their BS

There's alot of people out there good at selling things they don't know poop about

They like to BS the customers because they think they'll buy it

Make him look like the fool tell him you know what you're talking about

And then try to ask for a discount for being smart. :) It could work.

Good Luck

February 17, 2005

No, you're not on crack - this is just one of those confusing semantic issues that comes up when discussing lenses and formats.

Imagine taking a "normal" 50mm lens from an ordinary 35mm Nikon still camera (or Minolta, Pentax, whatever) with an image size of 24mm x 36mm and putting it on one of those nifty "half-frame" cameras (Olympus Pen, etc.) that were popular in the '60's and '70's. Those crammed twice as many pictures onto a roll of film because each individual image on the negative was only half the size of the Nikon. The "normal" 50mm lens would then produce a telephoto effect because the patch of film "seeing" it would only be half as big. Here's where the confusion comes in: when mounted on the half-frame camera, the 50mm would "look" like a 100mm lens on the Nikon. When sales people start saying "here's a 25mm lens that looks like a 50mm," or words to that effect, things start to get muddied up pretty fast. Of course, we know that a 25mm lens looks like a 25mm lens, period.

As for the 16mm/Super16 difference, the Super 16 frame adds width only, but no height. The horizontal field of view is increased, but not the vertical. You could say that a lens of a given focal length "looks" wider on Super 16 because it is seeing more at the left and right edges, but that's not all there is to it - there is an aesthetic difference due to the different aspect ratios - I much prefer the look of the wider frame.

Edited February 17, 2005 by Ian Marks

February 17, 2005

The way i understood it is if you are using wide angles,a 35 lens will appear "less wide" on a 16 camera.In other words a peleng 8mm fisheye looks more like like a 16mm fisheye on a 16mm camera.but the focal length is the same..just the angle seems less drastic because of the samller frame.

I figured this out because i've been looking for primes for my k3.

One guy did tell me that using 35mm lenses on a 16 are less sharp because they dont have to be on a 35 but since the frame are on 16 is so small they have to be very sharp. he said dont use 5mm lenses on a 16 camera.

i dont know if i buy that...maybe with cheap lenses but I've got a super takumar and I'm looking at some zeiss jenas and it seems to me an awesome glass is an awesome glass.if the c-mount bell and howell lenses on my filmo are sharper than a zeiss slr on a 16 then I've been misled.

I remember David Mullen putting me in check for worrying about super vs standard 16 qaulity when I'm using old cameras with c-mount lenses.(thanks man!)he implied I need better lenses and I think he's right .

David Mullen ASC · February 17, 2005

There are some sharp C-mount lenses but it's a bit hit or miss and you have to shoot them at their optimal f-stop.

February 18, 2005

Jeremy, David Mullen is the man - and his work is gorgeous.

I've heard a lot of conflicting information about using still camera lenses on a 16mm camera, but clearly plenty of people are doing it and some of them are pretty happy with the results (usually when using longer lenses, I've noticed).

I'm not sure that I agree that "awesome glass" will always provide awesome results - by that reasoning highly regarded lenses like the G-Claron Rodenstocks made for 8 x 10" cameras should provide great images on 16mm, but obviously the parameters in designing a lens to provide the best image across 80 square inches will be different than those for a 16mm motion picture film frame. It's obviously going to be easier to squeeze more resolving power out of lens designed to cover an area the size of a fingerprint! That being said, I've noticed that 35mm still camera lenses almost always perform measurably better at the center than out at the edges of the frame - at least when you use them for 16mm you're using just that best-performing center portion of the frame.

Some advantages - still lenses are cheap, as are the C-mount adapters. If you buy a range of lenses from the same manufacturer, they will usually have a standardized filter size like 52 or 55mm (these are cheap too) so you easily assemble an extensive collection of filters, including things like split diopters. Also, they effectively change your pokey C-mount camera into one with a quick-change bayonet fitting. Just leave the adapter on the camera. I've got a set of C-mount primes for my ACL and I've also got a set of Canon breech-mount SLR lenses, and the breech-mount lenses are much easier to interchange. The C-mount to Canon adapter ($20 on Ebay) effectively converts these lenses into presets, too.

Some disadvantages - compared to cine lenses, most still lenses are slow (although there are a lot of nice 50mm f1.4 lenses out there for $40-50), and many lenses exhibit a lot of "slop" when focussing - something you woudn't notice taking stills but which becomes an issue when trying to follow focus during a shot. That's because a lens that sells for $150 simply isn't going to built to the same standard as one that sells for thousands. Also, the aperture usually "clicks" from one setting to the next, making it hard to change exposure in mid-shot. Finally, wide angles are a problem when you consider that you have to get down to about 12mm to get a pronounced wide-angle effect (the 8mm Peleng seems to be the one path out of this dilemma).

A 35mm lens that will be slightly wide on a 35mm still camera (which is a format based on TWO 35mm motion picture frames) will provide a slight telephoto effect on 16mm.

With respect to the Peleng, I was seriously considering buying one. I don't know about you, but I love wide-wide angles, but really wide lenses that cover Super 16 are very expensive. At $200 or so, the Peleng seems like a contender. I understand that the fisheye effect is minimized when using this lens for 16mm or Super 16mm (because only a small center portion of the image is captured on film), but since the lens wasn't designed to keep straight lines straight, I was still concerned about barrel distortion. Luckily I located a 5.7mm Kinoptik at a good price and that lens is pretty incredible - and the straight lines are very straight.

If you go to http://www.longvalleyequip.com/lens.php, there's a pretty good discussion of this lens, along with an illustration of the results it produces on various formats, including Super 16.

Adam Nikolaidis · February 18, 2005

Thanks for the reality check, guys. I figured I knew better than this guy, but every once in a while I start thinking I'm crazy. Apologies for the confusion in interchanging "16mm" with "Super16mm." For what I was trying to get at they seemed effectively the same, but in retrospect I can see why it was unnecessarily confusing.

R8 Peleng: Excuse me, I think I need to go wipe some drool off the front of my shirt. I wonder if you could throw a shallow mattebox on if you were only using it for Super16. At $800, I'm listening...

-Adam

February 18, 2005

You should be able to snag a Peleng for about $200 or so off of Ebay (not $800), and with the 42m mount (a/k/a the Pentax screw), it will go directly onto your K3. And yes, I would rig some kind of lens shade to the front - you're only using a tiny portion of the image produced by the lens, so you don't have to worry about vignetting AND that bulbous front element is likely to produce a lot of flare. Let's us know how your shots turn out!

February 18, 2005

I love wide angles .I saw a clip on the k3camera.com site and it shows you exactly what the peleng does.its cool. kievcamera sells the peleng on ebay which I think is a very reputable dealer...

Would a 50 mm zeiss jena be sharper at that length than the k3s stock zoom?

The go for pretty cheap on ebay as do the massive 135mm ones.

Has anyone seen this?

http://owyheesound.com/owyheesound_instruc...ogorsk_k-3.html

looks pretty awesome.i dont know that i'd go anamorphic with a k3 when its so easy to change the gate but it actually looks cool with that rail. i wonder if you could put a pro matte box on a k3?

Laurent Andrieux · February 20, 2005

Didn't read the whole thread, but as to come back to its start, the basicr ule is that D.I = O.F where D is distance from camera to subject, I is the image size (works, either horizontal, vertical or diagonal) ; O is Object size and f focal length.

Also the view angle can be given by : tan (A/2)= I/2F where A is the viewing angle, I the image size (hor, ver or diag) and F the focal length. The reverse operation for tan is arctang and not cotang, and figures on your calculator as tan^-1, also mind it is ste to degrees if you want the angles in degrees...

Dominic Case · February 21, 2005

D.I = O.F

Or to elaborate, once you understand exactly what is meant by focal length, all the questions go away.

A simple concave lens (like a magnifying glass or a close-up dioptre), will focus parallel rays (from a distant object such as the sun) a certain distance away from it. That's its focal length. It will form images of everything else at that distance if they are very distant. The longer the focal length, the bigger those images will be, and therefore the less of the image will fit into a given frame.

Any camera lens behaves in the same way. While it's not intuitively obvious how you (as a user) can measure the focal length (whereabouts on the lens do you focus from?), you can calculate it from the image size as above). That's a little harder with a digital camera, becasue you can't take the image and measure it so easily.

Not even the marketing department of a lens company would attempt to get away with mislabelling focal length. The confusion comes when people don't know what focal length is and confuse it with a measure of field of view, not of actual image size.

Edited February 21, 2005 by Dominic Case