Moving Up To Zeiss Lenses... What Do I Do?

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Phil Maker

Well-known member
Here's the deal... I've only ever shot with zoom lenses. I have no idea how to use prime lenses. I'm shooting my next feature on the RED with a set of Zeiss standard speed lenses (18, 25, 35, 50, 85,). Forgive my lack of knowledge, but I have no idea what the hell to do with these lenses. I know these lenses are better than a zoom, and I'm ready to increase my knowledge, but I don't know what lens to use in each different situation. Can someone give me a quick tutorial on these lenses? Thanks!
 
Prime lenses are just lenses with fixed focal lengths. They are the same as the numbers on a zoom. (meaning the 35mm on a zoom is the 35mm prime length).

They (primes) are usually better then zooms because they tend to be more sharp and have less light loss. This is simply because it takes more lens elements to construct a zoom lens. This is less true in modern lenses as it was in the past.

The basics are all the same: The longer lenses will compress the background, while the wider ones will emphasize depth. Of course there are exceptions to that generality, depending on how you use them. Depth of field rules still apply. The longer lenses will have more shallow DoF, and the shorter focal lengths will have deeper.

Lenses are (generally) always sharpest slightly closed from wide open. If you don't mind the DoF change, go ahead and close your lens down by 2 stops. This should give a nice sharp manageable picture.

I think you should study up on how lenses work. They are all pretty much the same. Most zoom concepts are relevant with primes lenses... except for the obvious fact that primes can't zoom... you simply replace the lens with a new one.

I think all filmmakers should start with primes. It really forces you to think about lens selection and how different lenses will portray the same scene differently. Zooms tend to let this education slip by and helps encourage laziness. I've seen some filmmakers who never even consider moving the tripod. They just zoom in for the CU.... if they only took the time to consider the difference and make a judgement based on that artistic choice.
 
Good post Ryan, thanks. I've been looking forward to working with primes for some time now. In the past, I've never really had time to consider focal length because it's mostly always been run and gun. Now, with more narrative work coming my way, I'm starting to slow things down and really look for the best choice artistically. So let me see if I got it right. In most situations, say for instance, where I'm shooting a CU, and I want shallow DOF, I would maybe choose a 50 or an 85? Maybe 50 for CU and 85 for ECU? Also, can you recommend a good source where I can learn more about lenses? Thanks!
 
Huy Vu said:
Well, technically this isn't really true. Focal length doesn't affect DOF. Longer focus length just compresses the background more so that it appears to be blurrier.
Click to expand...

Technically you are wrong. Have you ever used a DoF calculator? What you meant to say was that the focal length does not seem to effect the DoF, when you keep the subject composition the same.

When you double the focal length and want to keep the subject the same size in frame, you must double the distance between it and the camera... in turn negating the change in DoF the focal length increase had decreased. The difference is, the background will be 'compressed'... meaning magnified. This lets us see the CoC effect much easier and the background appears more out of focus.

I call this the DoF Ying and Yang effect. Read about it in my article here: http://ryanpatrickohara.blogspot.com/2008/05/depth-of-field.html

PS: They actually do not cancel each other out perfectly and I have found that longer lenses and further camera to subject distance (with the same composition as a shorter focal length and closer subject to camera distance) actually yields shallower DoF.... although most likely not perceivable to the eye.

If you are not referring to keeping the subject size the same, focal length indeed has a major relationship with your DoF. It's not an illusion. Open one of the many DoF calculators I provide in the article. Make some settings and then only change focal length. You will see it's large influence.

Thank you.

-Ryan
 
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Phil Maker said:
Good post Ryan, thanks. I've been looking forward to working with primes for some time now. In the past, I've never really had time to consider focal length because it's mostly always been run and gun. Now, with more narrative work coming my way, I'm starting to slow things down and really look for the best choice artistically. So let me see if I got it right. In most situations, say for instance, where I'm shooting a CU, and I want shallow DOF, I would maybe choose a 50 or an 85? Maybe 50 for CU and 85 for ECU? Also, can you recommend a good source where I can learn more about lenses? Thanks!
Click to expand...

As Huy had tried to explain, if you want the frame to have the subjects forehead at the top and chin at the bottom, you will have to select a focal length and a subject to camera distance. These are almost directly related and will cancel each other out to a degree. Meaning if you have your composition but increase the focal length you are using by double you must double the distance of the camera away from the talent to achieve similar size of the subject in the frame. The depth of field will almost stay the same, except in this case have a small decrease. What will happen is that the background will be compressed. Meaning we will see a magnification of a smaller portion. This is what makes those large CoC blurs... appearing to be more out of focus.

Longer lenses do have shallower DoF, but it also depends on many more factors.


An understanding you must have at the onset of getting in deep with lenses is this:

If you have a Medium shot of a man with a wide lens, you can see lots of background. If you back the camera off double the distance it used to be and double the focal length, he will appear the same size in the frame, but you will see considerably less of the background. The background will still fill the same negative space the mans MS has always allowed. But this time it is a more magnified portion of the background, making the out of focus circles from the CoC more apparent.
 
I'm neutral here, but to set the record straight:

50mm @ f/2.8 @ 5 ft. = 4in dof
100mm @ f/2.8 @ 10 ft. = 4in dof
25mm @ f/2.8 @ 2.5 ft. = 4in dof

Technically you are both right, your are just presenting yourselves in different ways...yet saying the same thing. :)
 
Yes, but Huy can't just spit out a statement of generality like that. It's not good for people trying to learn.

If you are going to publicly declare that focal length has no bearing on DoF you must explain what you mean. Because when it's that open ended, it's a wrong statement. You must explain about keeping the subject comp/size in frame and how subject to camera distance relates.
 
Ryan Patrick O'Hara said:
Yes, but Huy can't just spit out a statement of generality like that. It's not good for people trying to learn.
Click to expand...

Sure, I'll bite. Your original statement "Longer focal length=shorter DOF and shorter focal length=deeper DOF" was pretty general too. Let the pot not call the kettle black.
 
Going back to your original questions Phil Maker:
Zeiss primes (I assume the usual super speeds not master or ultra primes) give you about two stops more to play with than a zoom. The red zoom for example, is a T2.8 (could be n F2.8 I can't remember), while zeiss super speed primes give you a T1.3 at widest aperture. That's a huge difference, and you'll find in location shooting that the primes will be a life saver because of lighting considerations. Prime lenses also have better minimum focus, meaning you don't have to be five feet away from a subject like those 12-120 angenieux or 10-100mm zeiss'. They also tend to "breathe" much less.
Those are the technical advantages of primes over zooms.
Modern zooms have a come a long way in terms of design, contrast, edge to edge sharpness, etc. but I still prefer a good set of primes. There's some panavision zooms and Fujinon Super Cine (HD) zooms I really like, and if they weren't so darn big I wouldn't mind just sticking one lens on the camera and shooting all day.
Oh, that's one more advantage - size. Primes are great for hand held. But they'll slow you down a bit, especially if you're not used to choosing the right one or you don't have a fast AC crew.
Just try to get your hands one the primes before the shoot to see what FOV they give you.
I believe Roger Deakins loves shooting with zooms among many DP's.
 
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