KODACHROME a question for photo engineers.

[Kirk Keyes]

Douglas Trumbull, [...] He gave a talk here in Rochester and everyone was so spellbound, the talk ran over by at least one-half hour if not more.

I wish I had been there for that. 2001 is my all-time favorite movie. I just bought the latest "special edition" 2001 DVD, but I need to talk my daughter into some TV time between Dora the Explorer episodes...

 

[Photo Engineer]

Kirk;

After his talk, I got to speak with him for 1/2 hour and then I left. I missed the next talk as a result of his overtime and my spending time with him so I was wandering around and saw him standing in the foyer to the conference. I went over and asked if there was a problem, and he said "looked like some mixup with my transporation so I'm waiting" and then we started talking again about SFX, Kubrick and etc. All in all, I spent nearly a full hour with him. One of his themes was (and here I will take a lot of flack) to encourage photography no matter what the medium, even though he was using essentially I-max (wide film) at a very high frame rate of over 60 mixed with digital.

 

[TerryM]

Uhm, how about the two of you call it a day and shoot this on a camera capable of 21fps? ...

This is hilarious! HA! HA! HA! HA! HA! HA!

ISO speed does dictate exposure requirements, but this can be with any combination of shutter speed / aperture, as long as it is the same EV. ie - as long as the film is receiving the correct amount of light! ...

I was wondering if you've ever shot K40 at higher speeds like 48 f/s (Fredrik said he's used 64 f/s), and if so do you consider the image quality at higher speeds to be as good as 24 f/s?

 

[Matt5791]

This is hilarious! HA! HA! HA! HA! HA! HA!



I was wondering if you've ever shot K40 at higher speeds like 48 f/s (Fredrik said he's used 64 f/s), and if so do you consider the image quality at higher speeds to be as good as 24 f/s?

Hi Terry - yes I've shot it at all kinds of speeds, including 54fps in a Nizo 6080 and at 70fps in the Beaulieu 4008.

Exposure is the same and looks the same, but the quality in terms of stability etc. overall is better, albeit in slow motion.

High frame rates can be used sometimes as a kind of low budget steady cam - it helps iron out the hand held work, especially if combined with a wide lens - its very effective.

Also, it means for a larger aperture again, and this helps with the smaller formats like 8 & 16mm in terms of creating a shallower DOF, if that is what you desire.

I remember using the beaulieu at 70fps a few years ago at Blackpool Pleasure beach (a theme park here, for want of a better description) on one of the roller coasters - with a wide lens and the camera held over my head this made for some great shots of the ride, looking accross everyone in from the back of the ride.

For anyone who knows the pleasure beach, this was on the Big Dipper - I definitely didn't attempt these antics on the 90 mph drop on the Pepsi Max!!

Matt

 

[TerryM]

... especially if combined with a wide lens - its very effective. ...

Matt, are you talking about those super-wide lenses of about 60mm & 65mm in diameter? That would definitely make a difference over a 30-35mm Lens as far as reducing Exposure Time. I didn't know you were talking about changing your Lens which was the point of our confusion. Very few S8 Cameras have removable lenses. Also, do your Nizo and Beaulieu have adjustable Shutter Angles?

 

[Matt5791]

Matt, are you talking about those super-wide lenses of about 60mm & 65mm in diameter? That would definitely make a difference over a 30-35mm Lens as far as reducing Exposure Time. I didn't know you were talking about changing your Lens which was the point of our confusion. Very few S8 Cameras have removable lenses. Also, do your Nizo and Beaulieu have adjustable Shutter Angles?

I don't really understand what you are saying, however you don't need to change the lens as virtually all super8 cameras have a zoom - when I say use a wide lens I mean by using the wide end of the zoom, this helps with stability.

Look through any camera with a wide lens and then with a long lens and see which is easiest to hold steady. Adding a high frame rate helps even more to smooth out any unsteadyness when shooting hand held (unless you can afford a steady cam of course, with operator)

The Beaulieu does have a C-Mount lens so you can change, but most people don't and stick with the Angenieux or Schneider zooms supplied as standard. The Beaulieu has an adjustable shutter angle - but you have to be careful as changing shutter angle introduces different effects. For example "Saving Private Ryan" was deliberately shot with a 90 degree shutter to give a particular feel.

A wide lens on Super8 is anything from 3mm to about 10mm.

Matt

 

[John Shriver]

Todd-AO cinema system used 30 frames/second.

 

[accozzaglia]

accozzaglia,

please keep in mind that this is an international forum and foreign members will have to look up abbreviations which are not photography related.

Sure thing, and I'll make note of it. With all due respect to you and others, this is a problem I deal with here, as well.

For instance, I run across the profuse usage (uhm, "laziness?") of other initialisms by APUG participants: even as my first language is English and despite having been online since the 1980s, some of these have left me baffled for the very longest time. So you're not alone. While my memory is tired right now, I can offer one example from the top of my mind: until I figured it out (after which point it became a grand annoyance, given its outright ambiguity) was "IDK". Evidently, its use here is is intended to mean "I don't know". This in my mind is just as valid a possibility as "I do know". So whrn I see this used, it fails to assist with clarity, because the ambiguity presents a direct dual opposition: either a yes or no.

This list could continue, but playing the grammarian card really misses the point: if you feel that the way in which I or another individual used slang was not accommodating, please understand that it is not out of malice or being deliberate. That said, I welcome you to send me a private message as a better way to confront it instead of using public admonishment. If you're in doubt about something, try out urbandictionary.com as your first stop. The most common uses for slang typically rank as their most popular definition for a particular word, phrase, acronym, initialism, or pidgin slang.

With that, let's re-focus on K-14 stuff. Cheers.

[edited for levity: I don't regard you or anyone else as "foreign". It gets in the way. Having something lodged in the back of my throat and requiring someone to provide the Heimlich manoeuvre? Now that's foreign.]

 

[TerryM]

K40 Exposure

Matt and Fredrik,
Can you recall what size Aperture you would generally use for shooting K40 at 24f/s or faster, and what is the Diameter of your Camera's Lens? For me with a 35mm Lens, the Auto Aperture was generally at f-1.8 to 2.8 with an 18f/s Exposure Time of 1/30th Second. So, as you can see, you can't go bigger than f-1.8, and so I couldn't even imagine shooting at 24f/s (if my Camera allowed it). :rolleyes:

 

[PHOTOTONE]

The "sunny 16" rule of thumb for outside daylight exposure-regardless of film format or cine or still-is f16 @ film ISO for shutter speed. If your cine camera at 18fps exposes at 1/30 sec, and your film is ISO 25 then your f-stop will be almost f16. I don't know where you get the f1.8 thing. With this rule in mind, running a camera at 24fps with the resultant shorter shutter speed, would still put you in the f8-f11 range or so, which would give you plenty of room to open up for "open shade" or "cloudy" conditions.

Back in the 1960's I shot plenty of Standard 8, and 16mm Kodachrome without a lightmeter, using this formula as my guide, and my film was properly exposed. The ONLY way you would deviate from this formula is if you had some light-reducing filters, such as Neutral Density, Polarizer or color balancing filters on your lens, and of course you would then have a filter-factor to figure in, but still I cannot fathom you having to shoot daylight Kodachrome at f1.8 outside. A lens f-stop is a lens f-stop, and cine lenses are often scaled in T-stops which are absolutely accurate, being the actual "transmission" of the light, rather than the "theoretical" transmission of the light. The focal length, the lens diameter, none of this matters in the least if you use the "F" or "T" stop scale on the lens you are shooting with. F16 on one lens will be f16 on another. Otherwise why mark the f-stops at all?

 

[TerryM]

... I cannot fathom you having to shoot daylight Kodachrome at f1.8 outside. ...

I didn't say the f-1.8 was "outside". That would have been indoors. The Auto Aperture constantly adjusts. I can't recall shooting 'bright sunny' scenes outdoors. An f-2.8 would have been approaching sunset in the shade.

 

[Fredrik Sandstrom]

Hi Terry,

I have shot K40 mostly in sunny weather, or overcast but still with plenty of light. Phototone is right about the f/8 - f/11 aperture range being the most commonly used. Sometimes f/5.6 in cloudy weather. Rarely wider than f/4 outdoors.

I can't understand why you believe the diameter of the lens has any significance. What diameter do you mean anyway? The front element or the barrel? My Schneider-Kreuznach lenses for my Bolex H16 are tiny. The built-in zoom lens of my 8mm camera is big (because it's a fast f/1.9 zoom). My 12mm f/1.9 lens for my other 8mm camera is tiny. But this is really not important.

 

[PHOTOTONE]

Hi Terry,


I can't understand why you believe the diameter of the lens has any significance. What diameter do you mean anyway? The front element or the barrel? My Schneider-Kreuznach lenses for my Bolex H16 are tiny. The built-in zoom lens of my 8mm camera is big (because it's a fast f/1.9 zoom). My 12mm f/1.9 lens for my other 8mm camera is tiny. But this is really not important.

Quite right,the diameter of a lens has absolutely NOTHING to do with its maximum f-stop or light gathering ability. If a lens is f1.8, it is f1.8.

 

[TerryM]

... What diameter do you mean anyway? The front element or the barrel? ...

Hi Fredrik,
I meant the diameter of the front glass sphere.

Quite right,the diameter of a lens has absolutely NOTHING to do with its maximum f-stop or light gathering ability. ...

I wasn't thinking of the f/stop. The diameter of the front Lens (glass sphere) dictates the amount of Light it captures from the scene. Using a larger diameter Lens is the equivalent of having more Light in the scene. That's why Space Telescopes are so large. They obviously can't increase the brightness of an object in Space, so they use a large Lens to capture more Light from the object. More Light decreases the required Exposure Time. If a given Lens at f/1.8 can't provide enough Light, a larger diameter Lens will enable you to avoid using a longer Exposure.

 

[Fredrik Sandstrom]

Terry, it sounds like you do not understand what the f-stop scale means. f/1.8 already tells you everything about a lens' light gathering ability (ignoring for the moment the slight difference between f-stops and T-stops). It is true that in general a faster lens (smaller f-number) needs to have a bigger front element, but many other factors come into play too. Bottom line: An f/1.8 lens with a larger front element does not gather more light than an f/1.8 lens with a smaller front element. If the smaller lens did not gather as much light as the bigger one, then it wouldn't be f/1.8.

Have you ever used a handheld light meter? What are the parameters that it deals with? They are ISO, aperture (f-stop), and exposure time. Not lens diameter. Why not? Because it is completely irrelevant.

 

[railwayman3]

Hi Fredrik,
I meant the diameter of the front glass sphere.

I wasn't thinking of the f/stop. The diameter of the front Lens (glass sphere) dictates the amount of Light it captures from the scene. Using a larger diameter Lens is the equivalent of having more Light in the scene. That's why Space Telescopes are so large. They obviously can't increase the brightness of an object in Space, so they use a large Lens to capture more Light from the object. More Light decreases the required Exposure Time. If a given Lens at f/1.8 can't provide enough Light, a larger diameter Lens will enable you to avoid using a longer Exposure.

When I started in photography, it took me a long time to understand f-stops,
and I think that Fredrik's explanation covers the issue.
Just to try to be helpful and amplify this a little, consider the situation of a subject where I measure the correct exposure (with a hand-held meter) as, say, 1/500th at f/2.8 on 100ASA film. That exposure will still be correct for whatever camera/lens I use, and whatever the physical diameter of the glass of the lens....and there could be a vast difference between various f/2.8 lenses, from a tiny lens on a sub-miniature to a huge lens on a 10x8. And there could be a difference between f/2.8 lenses for the same format...for 35mm, think about the large diameter of an extreme wide-angle compared with a standard lens. Yet, if each is f/2.8, the exposure will be the same for the same shutter and film speeds.
.

 

[mts]

Diameter of the lens affects light gathering power (the number of photons collected in a given time). Larger diameters reduce exposure time for point sources only, i.e. stars because the collected photons are directed toward the same point. The f/ratio applies to extended sources. If you photograph stars then you simply want larger aperture. If you photograph scenes (or galaxies and nebulae) then you often need lower f/ratio. If you need both, then you need a special optical design, for example the Schmidt camera that is a combination of reflecting and transmitting optics and unfortunately has a curved focal surface.

For ordinary photography you generally want faster optics but must be aware that lens aberrations are greater with faster lenses. That is why you typically stop down the lens to increase depth of field and obtain sharper images. Also flare and scattered light is always worse in a faster lens because there are generally more glass elements and more strongly curved surfaces.

 

[TerryM]

Thanks Fredrik, railwayman3, and mts;
I believe that Fredrik and I have been talking about two different things. Here are a few quotes from Wikipedia to help you understand what I'm talking about.

"For a thick lens (one which has a non-negligible thickness), or an imaging system consisting of several lenses and/or mirrors (e.g., a photographic lens or a telescope), the focal length is often called the effective focal length (EFL), to distinguish it from other commonly-used parameters:
Front focal length (FFL) or Front focal distance (FFD) is the distance from the front focal point of the system to the vertex of the first optical surface.
Back focal length (BFL) or Back focal distance (BFD) is the distance from the vertex of the last optical surface of the system to the rear focal point."

"The pupil diameter is proportional to the diameter of the aperture stop of the system. In a camera, this is typically the diaphragm aperture, which can be adjusted to vary the size of the pupil, and hence the amount of light that reaches the film or image sensor. The common assumption in photography that the pupil diameter is equal to the aperture diameter is not correct for many types of camera lens, because of the magnifying effect of lens elements in front of the aperture."

"The term stop is sometimes confusing due to its multiple meanings. A stop can be a physical object: an opaque part of an optical system that blocks certain rays. The aperture stop is the aperture that limits the brightness of the image by restricting the input pupil size, while a field stop is a stop intended to cut out light that would be outside the desired field of view and might cause flare or other problems if not stopped."
----------------------------------------------------------------------------------

Terry, it sounds like you do not understand what the f-stop scale means. f/1.8 already tells you everything about a lens' light gathering ability ... It is true that in general a faster lens (smaller f-number) needs to have a bigger front element, but many other factors come into play too. Bottom line: An f/1.8 lens with a larger front element does not gather more light than an f/1.8 lens with a smaller front element. If the smaller lens did not gather as much light as the bigger one, then it wouldn't be f/1.8. ...

Fredrik, the Back Focal Length does not tell you the Diameter of the Front Lens. The Back Focal Length is related to the curvature of the last Inner Lens. The Diameter of the Front Lens is directly related to the Pupil Diameter referred to in the quote. I've called the "pupil" the Aperture, and perhaps I've confused you by using the term "Aperture".

mts, did I explain this correctly?

 

[Q.G.]

Fredrik, the Back Focal Length does not tell you the Diameter of the Front Lens. The Back Focal Length is related to the curvature of the last Inner Lens. The Diameter of the Front Lens is directly related to the Pupil Diameter referred to in the quote. I've called the "pupil" the Aperture, and perhaps I've confused you by using the term "Aperture".

mts, did I explain this correctly?

I'm not mts, obviously , but will answer that: over all, no.

The diameter of the front glass can set a limit to the amount of light a lens 'gathers', yes.
But (simplifying) the amount that a lens let's through is set by the diameter of the entrance pupil that was mentioned before.
The f-number (which is the measure for how much light a lens lets through) is directly related to the diameter of the entrance pupil and the focal length.

And that is an important thingy: my f/4 40 mm lens has a much larger (2x) diameter front lens than my f/2.8 80 mm lens. So the lens with the smaller diameter front lens lets more light through.
My f/2.8 50 mm lens however has a front lens that is about equal in size as that of the f/4 40 mm. Yet they do not both let pass the same amount of light.
The diameter of the front lenses of my f/2.8 150 mm and f/2 110 mm lenses also are about equal in size. And again, not equally bright.

So obviously the diameter of the front lens is not all important.

Now look at the pupil diameters: the diameter of the entrance pupil of the 40 mm lens is 10 mm, that of the 80 mm lens is 29 mm.
Divide 40 by 10, 80 by 29, and you'll get the f-numbers.
The differences in lens speed between the other lenses mentioned also reveal themselves when you look at the diameters of their entrance pupils and relate those to the focal length.

So the diameter of the front lens is not (!) directly related to the diameter of the entrance pupil.
It's a bit more complicated.


The purpose of large diameters in astronomical telescopes is not to increase the light gathering power, but to increase the resolution.
The larger the light gathering surface, the smaller the distance between two objects can be while still being seen as two distinct objects.
Or rather: the greater the maximum distance between the light gathering 'bits', the greater the resolution. You can combine small telescopes, creating a 'diameter' much larger than would be possible if only a single telescope had to be used. The greater the distance between the two, etc.
Such an array does not do much to increase the amount of light gathered, but it performs small miracles for the 'quality' of the light.


"Back focal length" is really a wrong term to use. I like "back focus" a bit more, but the German term "Schnittweite" a lot better. "Schnittweite" obviously contains no reference to focal lengths, and thus avoids confusion.
It's too easy to confuse the distance between last lens element and film plane (which is what is meant by the term) with the focal length, when the term for the first also contains the words "focal length".

The rear focal length (= the distance between the rear principal plane of a complex lens and the image plane when the lens is set to infinity) can be much greater than the "Schnittweite" (in telephoto constructions), or much smaller than the "Schnittweite" (retrofocus constructions).
In (near) symmetrical lenses, the rear focal length is a bit larger than the "Schnittweite", the difference being about half the distance between first and last lens surface.

So in a complex lens (or even a simple, but thick lens), the rear focal length and the distance between the last lens and film plane never are the same.
So why use the words "focal length" in a term to describe the "Schnittweite"?

 

[TerryM]

... But (simplifying) the amount that a lens let's through is set by the diameter of the entrance pupil that was mentioned before.
The f-number (which is the measure for how much light a lens lets through) is directly related to the diameter of the entrance pupil and the focal length. ...

Q.G., does the International Standards Organization (ISO) dictate what illumination / amount of Light is supposed to pass through a given Aperture f/number? If not, I don't see how you can be guaranteed that every Lens will be equivalent for a specific f/number. The Wikipedia quote above mentions the problems with Aperture / Pupil diameter for different Lenses.

 

[Q.G.]

I don't know what, if there is one, an ISO-standard says about the subject.

I do know that they have abandoned the T-stops, and that for a reason:
With coated lenses the loss due to reflection is very low, and not something to worry about. Nothing you would ever notice.

Anyway, the diameter of the front lens is not directly related to either the f-stop nor t-stop.

(By the way, on a general note: be careful with Wikis. They are full of errors.)

 

[TerryM]

... Anyway, the diameter of the front lens is not directly related to either the f-stop nor t-stop. ...

What about a scenario of a single-glass Lens -- comprising just the outer Lens. Now take two such Lenses with the same curvature and Focal Length: one Lens is 20mm in diameter, and the other is 40mm in diameter. The diameter of the Pupil Aperture would of course be the same for both Lenses at all f/stops. Under the Reciprocity rule, wouldn't the 40mm Lens be providing four times as much Light as the 20mm?
Here's the Wiki Reciprocity Article:
http://en.wikipedia.org/wiki/Reciprocity_(photography)

(By the way, on a general note: be careful with Wikis. They are full of errors.)

I'm always concerned about Wiki too :confused:, but they generally have professionals handling specialized topics.

 

[Q.G.]

What about a scenario of a single-glass Lens -- comprising just the outer Lens. Now take two such Lenses with the same curvature and Focal Length: one Lens is 20mm in diameter, and the other is 40mm in diameter. The diameter of the Pupil Aperture would of course be the same for both Lenses at all f/stops. Under the Reciprocity rule, wouldn't the 40mm Lens be providing four times as much Light as the 20mm?

A simple lens double the diameter of another simple lens will pass more light, yes.
That, because the entrance pupil will be larger too.

But now go to the Wiki article, and try to figure out what on earth Bunsen and Roscoe's reciprocity would have to say about that.
(should you be in a hurry, the answer is: absolutely nothing. )

 

[alan doyle]

http://freeforumzone.leonardo.it/discussione.aspx?idd=7155592
a new reason to love old kodachrome.
looks like new generation scans.
lovely.

 

[bobwysiwyg]

Alan,

Great pics, thanks for posting.