Zooms and Primes

Mwjace

Mwjace

Active member
I want to start off by saying that i am a Video guy born a raised. I haven't done any "Real" film work. so coming to the F3 and playing with it i have some questions.

First some background. We recently got 2 F3s on our campus one we have a Red 50-150 Zoom on it. the other the 3 standard sony prime lenses. our plan was to augment the sony prime with Ziess cp.2 18 21 and 100mm. After viewing extensive tests we determined that for the most part the sony, ziess, and red lenses all match pretty well with each other.

I took the 2 cameras out for some testing. As a video guy it became apparent the i prefer a zoom lens to prime lenses. it's more what I'm used to, right. If i need to reframe just a bit i can zoom in or out. with primes i have to move the camera or change a lens. With all the extras added to the camera it was a pain to move the whole rig in order to get the right frame.

So my my real question to you Cinema Pros, what are the advantages to useing primes over zooms especially when I'm comparing cp.2 and red lenses. they both give me relative fast speeds and match quite well, but with a zoom i don't have to change a lens every time i need a different focal length.

Another though is i can get 2 red lenses that cover 17-150mm for around 14,500 where as if i were to get the Ziess to cover that same range I'm spend around 24,000.

i hope you can educated this poor uniformed video guy and help me out.

Thank you all
 
It sounds like for your style of shooting zooms may be more efficient.

Primes are optically less complex, simpler to fabricate, and therefore, are considerably cheaper and lighter than a zoom of the same optical quality and mechanical build. Zooms tend to need more light than primes (they're not as fast).


In the video world of event, ENG, reality, documentary, and other field shooting zooms tend to provide speed and flexibility.

In the film world, where time is taken to set up controlled shots, and talent is blocked and controlled, there's no speed advantage to a zoom, and unless the shot calls for a zoom, it makes sense to use a prime for it's weight, fast T stop, and sharper optics.
 
Have you considered still zooms? They offer extreme image quality since they work on 20+ Mpix still cameras, are light, fast, cheap and offer ranges unheard of in PL zooms.
at 2mpix frame(1920x1080) you are nowhere near performance limit of any modern lens- be it zoom or prime.
 
Viddovation said:
Primes are optically less complex, simpler to fabricate, and therefore, are considerably cheaper and lighter than a zoom of the same optical quality and mechanical build. Zooms tend to need more light than primes (they're not as fast).
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Yes and no.

Primes are less complex mechnically, but they often put more effort into optical quality.

The red zooms breathe a little more than i'd like. The CP's will breathe less, be faster, and smaller.
 
Technically, zooms will never be optically superior to primes.

Yes, some zooms are better than some primes... but for every good zoom, there is a better prime.

Zooms require many more elements in the design, thus, if you were to technically find the best glass in the world, coat them with the best coatings, and then build a zoom and a prime... the prime will likely have 10 elements (average Cooke s4 has 10-14 elements) while the zoom might have more around 22 elements... and every time light has to pass through a surface, the light, will reflect, absorb, or refract in very small amounts. Lens coatings are the reason this happens in small amounts. Before lens coatings, lenses were absolutely insane. Light loss in transmission, shading, flares and contrast reductions plagued the cameraman.

Today we have lens coatings that instead of reflecting 4% of light per element, reflect .1% (Cooke coatings)... can you believe that?!

Here is an article written by William Stull, ASC regarding the first successful testing of lens coatings in 1940:

William Stull: Lens Coatings, 1940


From American Cinematographer, Non-Glare Coating Makes Lenses One Stop Faster by William Stull, A.S.C (March 1940)

For many years photographers have accepted the fact that a considerable proportion of the light that enters a lens never reaches the film. The greater part of this loss is occasioned by reflections from the various polished glass surfaces- inside and out- that make up the lens, and it increases with the increase in the complexity of the lens' design.

Thus the loss is considerably greater in many of the modern, complex high-speed lenses than in the simpler, older objectives. But since lenses depend for their action upon the use of many highly polished- and therefore reflective- glass surfaces, it has seemed that nothing could be done to avoid these losses.

Almost exactly a year ago, two Eastern research groups, working quite independently of each other, separately announced the development of methods of treating glass to eliminate surface reflections. That this created a sensation in photographic circles would be to put it mildly.

Here was the development so radically advantageous that it would practically revolutionize photography! But the excitement subsided when it was learned that in both cases the project was still in the experimental stage: that while lenses could be treated, the treatment was extremely delicate and not at all lasting.

Paramount Pioneers

Today the subject takes on renewed interest when it is learned that the stage of commercial practicability that the Paramount Studio has been using a set of treated lenses on actual production, with such excellent results that treatment of all the studio's lenses is being contemplated.

The process used is that developed by Dr. John Strong of the California Institute of Technology. Essentially, this consists of depositing upon each of the glass surfaces treated an ultra-microscopically thin chemical film. This film measures but four millionths of an inch (0.000004 inches) in thickness- exactly one-quarter the length of a light-wave.

As light falls upon this film, rays are reflected from both its upper and lower surfaces. Since the coating is exactly one-quarter wave-length in thickness, these reflections from the upper and lower surfaces are equal in intensity, and opposite in phase. What follows is similar to the well known interference effect in that these oppositely phased reflections cancel each other out. However, classic scientific theory does not account for the fact that with this treatment there is an increase in overall light transmission, which would occur if these reflections merely offset each other.

Some of the processes announced a year ago, produced this coating by immersing the glass surface to be treated in a tank of liquid on the surface of which was an infinitely think film (one molecule thick) of an insoluble soap.

Forms Permanent Coating

Repeated immersions or dippings, approximately 22- built up the desired quarter-wave-length coating. It was still, however, a delicate, soapy film, with all the inevitable drawbacks of a soap-film.

Dr. Strong's method, however, is different. In this, the desired surface coating is deposited by evaporation in a vacuum. Instead of a soap-film the coating is a metallic fluoride. While the details of the Strong process cannot, of course, be given as yet, it may be stated that the present treatment produces a coating sufficiently durable to withstand any normal handling.

Some of the lenses used at Paramount have been washed to remove accidental fingerprints, without in the least disturbing the non-glare coating.

In addition, exhaustive tests by the optical experts of the studio's engineering staff indicate that the treatment is in no way harmful to the normal optical qualities of the lens. It is non-corrosive, non-tarnishing, and does not pit or scratch the glass surface. It is further stated that the expense of treating lenses is not prohibitive.

The practical advantage gained from using treated lenses are many. Probably the most startling is the increase in effective speed. Normally there is an average light-loss of 5.22 percent from reflection for each air-to-glass surface inside or outside the lens: thus with a typical high-speed motion picture anastigmat like the Astro "PanTachar," which has eight such glass-air surfaces, the loss of light from reflections is in excess of 41 percent.

If such a lens is treated on all its external and internal glass-air surfaces, this loss is reduced to negligible proportions.

Increased Shadow Detail
But this accounts for only part of the actual gain in speed. Much of this reflected light finds its way back to the film as scattered, fog-producing light which tends to veil the shadowed areas. With this scattered light eliminated, it is possible with a given exposure to record a great deal of shadow detail which is normally lost.

Conversely, it is possible to obtain a given effect, as measured by shadow detail, with considerably less light than would be needed to give the same effect with an untreated lens.

These two gains are cumulative, and add up to a practical increase in speed of virtually one full stop, or between five and six printer-light settings in the Paramount laboratory. Thus a normal f/2.3 lens, when treated is the equivalent in speed of an f/1.6 objective, but still retaining the depth of field, definition, and optical quality of the f/2.3 design!

The elimination of the internal reflections gives a marked increase in the apparent definition of scenes photographed with treated lenses. The effect may be compared to that seen when using a fast lens with and without an adequate sunshade. The picture as a whole is visibly more crisp, and details not previously evident are suddenly revealed.

In the same way, depth of field is apparently considerably increased by the treated lens. It is quite possible that the circle of confusion is affected, since the resolving power is known to be increased.

Shooting Into Lights

Every photographer is familiar with the lens-flare which ordinarily results from shooting directly into strong sources of light, such as the sun or a studio lamp. The reflections from the several glass-air surfaces of the lens produce multiple, distorted images of the light-source or the iris diaphragm, usually with strong secondary halation streaks.

Comparative scenes filmed though treated lenses show an almost complete absence of these effects. Instead, a surprisingly clear image of the scene and the light source is obtained: such halation as is present is obviously photographic rather than optical, and attributable to photographic overexposure and to reflections from the film base itself.

The practical advantages which this treatment offers to cinematography can be well imagined. The increased speed can be of tremendous value in simplifying lighting. The increases in depth and definition should be of almost equal benefit under modern conditions, especially in the case of "follow focus" and dolly shots.

It may be mentioned, too, that insofar as can be determined as yet, the use of treated lenses should be equally feasible in natural color cinematography, in Technicolor or an other process. While a treated lens, if examined in the hand, by reflected light, appears to have an iridescent magenta sheen, the coating does not appear to have the slightest effect upon the actual color transmission of the lens, nor upon its color correction.

Other Uses

The visual image viewed on the focusing screen of a camera shows no trace of color alteration, and monochrome tests of standard color charts made under identical conditions with treated and untreated lenses show no difference in color rendition. It may therefore be assumed that the treated lenses may be used equally well in color photography; and due to the inherent limitations in speed and definition of all color processes, they could be used to even greater advantage in color than in monochrome.

Naturally , this non-glare treatment need not be confined solely to motion picture camera lenses. It will be equally beneficial when applied to the lenses of still cameras, optical printers, projection lenses, and the like, while the advantages to be gained from applying the treatment to the optical systems used in recording and reproducing sound, where speed and extreme resolving power are so necessary, should be equally revolutionary.
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So until you can create a zoom lens that has as many elements (or less) of that of a prime... it's not possible.

With that said, shooting 1080p can hide the extra sharpness and other benefits of a cine-prime over a cine-zoom. Regardless if anyone can see it on screen, if you get all technical dork about it, zooms are not as good as primes in quality.

But a good zoom may be quality enough for you. I'm not saying you should go zoom or prime, that is to be decided by many other factors. I'm just clearing up a technical truth.
 
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1940? jeez, a little out dated you'd think. Even within last 10-15 years there is a technological leap in lens design and maufacturing. FYI the broad band coatings are as much as 99.8% efficient so the difference f and t- stops are negligible even for a zoom.
On top of that the MTF response falls off much quicker for the OLFP filter than that of the lens ( to prevent aliasing) as the threshold resolution is approached so, especially for 1080p work the lenses are a serious overkill (which is definitely a good thing)
 
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Yeah, that's an old article from a March, 1940 American Cinematographer magazine... but my point of the article was to show how things used to be and the effectiveness of even the first lens coatings. And regarding F-stops and T-stops, I've found they are not negligible, IMO. Then again, I'm not using brand new photography glass, so maybe it's because they were made in the 80's. I don't know.


And yes... most cameras, especially 1080p and DSLR Video cannot resolve enough to tell a sharp lens from the sharpest. But regardless, primes are better optically... despite if you can see it or not. That was my point. Not saying they were better for the OP, just saying.
 
Not to be argumentative but rather to set the record straight I'm yet to find a prime that is as sharp in the same fl range as the 14-24 F2.8 Nikkor or on the high end 17-80 Angenieux T2.3. From what I have seen even a Master Prime, even at 2.8 is about the same. For over 10 times the price and three times the size (in case of Nikkor).
I've projected all these many times and have seen myself- not a hearsay...
I don't thing that the traditional "primes are always better than zoom" holds water today. The economy of scales has pushed zooms much farther than primes and it shows.....
 
There is an aesthetic dimension to this as well. A particular focal length carries with it elements of a visual grammar (perspective, field of view, dof, etc.) that are consistent. As you start zooming for convenience instead of framing properly for the fl appropriate for the shot on an aesthetic level, then you are introducing inconsistencies in rendering the scene.
 
optitek said:
Not to be argumentative but rather to set the record straight I'm yet to find a prime that is as sharp in the same fl range as the 14-24 F2.8 Nikkor or on the high end 17-80 Angenieux T2.3. From what I have seen even a Master Prime, even at 2.8 is about the same. For over 10 times the price and three times the size (in case of Nikkor).
I've projected all these many times and have seen myself- not a hearsay...
I don't thing that the traditional "primes are always better than zoom" holds water today. The economy of scales has pushed zooms much farther than primes and it shows.....
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Isn't thinking that a zoom could technically be sharper than an equivalent zoom is defying physics? Right?

I didn't say that a zoom can't be better than a prime... I'm saying that zoom technology requires more elements inside the lens. I don't see how if using the same glass and same coatings, a zoom lens with 22 (44 surfaces) elements could out resolve the same glass and coatings of a prime at 10 elements (20 surfaces). They could be close enough for the most discerning eye to not mind either, but in the world of physical properties and how light works, I'd think it is really a matter of physics.
 
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Unfortunately engineering doesn't work this way. Glass shape, material type, coatings are all part of the each individual lens design so there is no such a thing as zoom and prime made from the same elements, but more for the zoom. If there was , you'd be right but I haven't heard of it.
I think we've strayed too far so I digress...
 
Optitek, you are obviously a man in the know with regard to lenses, but I think what they are referring to in part is a situation where you can get a nice sharp 35, 50, 85mm set in the F1.4 range at a reasonable price (even from the Nikon line), but a 28-70mm zoom is probably going to be F2.8 wide open (from several manufacturers). Plus the wide open zoom is likely to suffer at F2.8 while those primes are going to be tack sharp at F2.8. And I just love the 105mm F1.8 nikon prime.

Maybe Cooke or something like that for $6,000-$12,000 can do it. But most of us don't get to experiment with such lenses. Timur and Tom being exceptions.

That being said I'd surely like to hear your opinions on the best lenses out there for $2,000 each. You mentioned the 14-24mm Nikon. (Does that lens distort?) Any others?
 
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Giuseppe Pugliese dop

Giuseppe Pugliese dop

I believe that if you come from an ENG type background you're going to be much more at ease with a cine-zoom rather than a prime lens set.

With that said, you're going to be looking at spending a lot more money for a GOOD zoom than a good set of primes. The really nice and sharp zooms with little distortion are in the $30k + mark. you can get a set of new primes starting around $16k




Giuseppe Pugliese dop
 
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