Lens Questions

C

CMS

Member
These are very simple photography questions, but I need to start somewhere. I would appreciate any help I can get from this excellent community.

Recently I had a chance to play with an XL2 and 14X manual lens. I've never done any photography before, and I'm used to the lens on the AG-DVX100 where there are no marks on the lens.

Could someone tell me what the marks for feet/distance on the lens is for? Why would it be on the lens rather than in-camera? I mean, if I'm turning the lens to obtain focus, should I be looking at the lens marks for some reason too?

I realize what the f-stop numbers are but the rest I'm unsure of...

This must be a funny question for those from a film background - I'm used to the consumer spinner rings!
 
Re: Lens Questions

The foot/meter marks are where the camera is focusing. Meaning that the camera is focused on a point exactly that far away from the image plane. You set your lens to 14'...then it will be focusing at a point 14 feet away from the CCD.

One of the many reasons the marks are on the lens is because a manual lens typically doesn't have any electronic method of transfering that data to the camera. It would be cool if a twist of the barrel would result in a digital display in the viewfinder, but that just doesn't happen.

Usually you have a 1st Assistant Camera pulling the focus on your lens while you're operating the camera, thus he needs to read the numbers on the barrel to know where he is.
 
Re: Lens Questions

The biggest single reason for focus markings on lens barrels in todays digital world of auto everything is tradition.

Once upon a time, cameras (using film) were not reflex and so you focused by estimating the distance and setting the focus and hoping the depth of field covered your subject.

Cameras were eventually designed with focussing aids of various types but in the movie world accurate markings with witness marks (actual index lines under the numbers) to show the exact distance from the film plane of the camera to the point of focus became the norm allowing you to use a tape measure to the subject and accurately set the focus.

You will notice that still camera lenses and video lenses that have footage numbers do not have witness marks, the numbers being a guide not a reference.

Motorized and servo lenses with no direct mechanical link between the focus ring and the mechanism that rotate endlessly do not lend themselves to any markings on the ring at all.

Video lenses that do have markings denote the distance from the front of the lens not the image plane (the object distance) - except for a few very pricey film style lenses made for film-style video production that have witness marks measured from the image plane .

Bill Turner
Century Division
Schneider Optics
 
Re: Lens Questions

..i wouldn't really call them useless. id much rather have them there then not whenever possible.. they are fast and easy to double check things without walking around the camera. and are really a nice visual guid and reference for changing or setting up things on the fly if you happen to have the markers in your camera turned off or covered up.
 
Re: Lens Questions

Thanks for the excellent explanations, understanding it better now, enough so that I'm sure I can tell someone else in the future. I have another question though:

"Video lenses that do have markings denote the distance from the front of the lens not the image plane (the object distance) - except for a few very pricey film style lenses made for film-style video production that have witness marks measured from the image plane."

Would the Canon 14X manual lens fall in this category? Where would one measure from on this lens, toward the front or somewhere further back wher the image plane is? Where is the image plane on such lenses anyway?
 
Re: Lens Questions

CMS,

I've been considering the 14X Manual but many folks have been pushing me towards the 16X. Since I can't decide, I'm still on the sidelines. How do you like the 14X?

Thanks,

Matt
 
Re: Lens Questions

Dear CMS, the Canon 14x and 16x lens are typical video lenses, done in the style of broadcast camera lenses. The have numbers but no index lines , the numbers indicate the distance from the front of the lens- the camera has no image plane marked on it in any case- and where is the exact point to set the focus , the middle of the number?

The film style lenses for high end broadcast camera and HD cameras typically cost over $15,000 and the focus scales are custom for each lens in most cases.

Bill Turner
Century Division
Schneider Optics
 
Re: Lens Questions

Hello MattC, I've enjoyed reading more than a few of your posts here, some good questions and advice alike.

I can't really say yet about the 14X manual - I just had a chance to check one out with the XL2 but don't have one for myself. I've never tried the 16X.

From what I could tell, I really like the manual XL2 setup - that is definitely the direction I'd like to go.

Compared with the AG-DVX100A with Century Optics Focus Ring, I like the feel and control on the "true manual" lens better. Plus everything I'm reading on photography is becoming easier for me to understand. I dunno, it's easier to understand f-stops, etc with a manual lens instead of through a menu and with a digital readout. And I don't like how the Century Focus Ring tends to move around after some use, even after tightening the screws.

Actually, this was my general impression of the XL2 - seemed like the learning curve was easier - but then again, this could be because I've spent time with the AG-DVX100  ;D. I have a ways to go still though as you can all tell.

I do miss the focus scale in the viewfinder though. Don't think the 14X sends this info to the camcorder. And I think the lack of ND filters built in will affect me where I live. Usually very sunny.

The biggest drawbacks of the 14X I think is the lack of ND filters and that you can't mount a clamp-on matte box to the front. You'll need rods for sure. So just to use ND filters and a matte box, you'd need a rods based matte box and you'll have to buy 4X4 ND filters that already comes in the 16X lens or in the AG-DVX100A.
 
Re: Lens Questions

Hello Bill, thanks for your help and replies! I read elsewhere that you're the resident lens guru and I'm glad to read your posts.

The Canon video lenses are still small time then  ;D

I'll measure from the front of the lens if ever I need to...

Thanks again.


Charles
 
Re: Lens Questions

Bill,

Question: How important are those lenses (say the 15G one compared to the 16x) in determining the quality of a shot?

Let's say you were filming something in 35mm, and all other things being equal, you shot one shot with the expensive lens, and one with the video lens. How big a difference in image quality would there be?

c.g.
 
Re: Lens Questions

Dear c.g._eads,

I am not sure I understand your question. The biggest single factor in the quality of an image(assuming quality means primarily resolution) is the size and limiting resolution of the recording media.

35mm is better than 2/3" video because of the size and resolution of the 35mm format not the lenses. The video lenses do not produce an image large enough to allow them to be used on 35mm film so any discussion about how a video lens would perform on a film camer vs a film lens seems pointless, unless I am missing something, which is always possible.

Bill Turner
Century Division
Schneider Optics
 
Re: Lens Questions

yeah, my understanding of lenses is limited, so I guess that didn't come out right. So let's start over.

Say you're filming a 35mm feature. That being said, what's the difference between using one of these really expensive lenses, and a cheap one? I mean can the average person really tell? Or do things like lighting and production design have a more of an effect over the look of the shot.
 
Re: Lens Questions

Dear c.g._eads

I am not sure I feel qualified to answer your question, assuming I understand it correctly. MY OPINION, is that the talent of the director, Directory of Photography, operator, lighting techs is more important than the equipment.

Citizen Kane was shot with a non-reflex camera and lenses that are quite poor by today's standards. I think that one should use good equipment because all things being equal, why not record the best images your budget will allow?

For the most part, the quality of most modern lenses is quite good, but the best lenses have better contrast, edge to edge sharpness (especially wide open) than their less expensive cousins. The mechanical contruction is also better. In lenses you tend to get what you pay for.

As a generalization if you shoot everything between F5.6 and f11 the differences in optical quality are reduced.

Bill Turner
Century Division
Schneider Optics
 
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