View Full Version : Lenses


MadMan
05-17-2008, 01:28 AM
What lens is there that has everything i focus (like a wide angle lens) but isn't toooo wide angle? So pretty much a lens with everything in focus and that i don't have to be like 2 feet away from the actor to film a normal shot of him.

Rankles
05-17-2008, 04:31 AM
I'm not sure you're too certain on how lenses work.

I only really know about Arri lenses at the minute, and high end ones at that but in terms of your question there will be many lenses that fit that description and there are many factors that determine depth of field, not just the lens itself.

If you wanted everything in focus in a shot (although if the shot has things in the distance this will look cluttered and distracting) you can't really get that whilst being two feet away from an actor because to have him in focus at that distance will throw everything out of focus past about two feet behind him.

Can you describe the shot in more detail? If he was against a wall, say, and you wanted the wall posters in focus then any wide angle lens would do.

MadMan
05-17-2008, 08:20 AM
ok...... well instead of me describing what i want can someone tell me where i can read about lenses and how they work???

oakstreetphotovideo
05-17-2008, 10:24 AM
Depth of field (what you want lots of) is dependent on 3 things:

1) the size of the aperture opening in the lens; commonly referred to as the f-stop. On video cameras the aperture is also called the iris.

2) the distance from the focal plane (in the camera) to the subject

3) the size of the focal plane (CCD or CMOS sensor on a digital still/video camera, or size of film stock on a film camera)

(DOF appears to be affected by the focal length of the lens, but that is an optical illusion. Visually however, it does have an affect because distances are compressed by longer lenses, so you may still want to consider it a factor)

regarding # 2, the further your subject (focus distance) is away, the more depth of field you will have.

regarding # 3, smaller focal planes yield more depth of field. e.g. a 1/4" CCD video camera has a lot more depth of field than a 1/2" CCD camera, which has a lot more depth of field than a 35mm (~1.4") film camera (or Red One).

What you are looking for is called "hyper focal distance", google that in quotes. The hyper focal distance of a lens is the focusing point at any aperture that yields maximum DOF. If you use hyper focal distance at f16 on a 35mm camera with a 50mm lens, the acceptable focus range will be from about 8ft to infinity. I've used this technique a lot shooting landscape photos.

You may want to also research "depth of field", also. Focus is relative, because only one plane is technically in sharpest focus at any one time. We measure DOF subjectively as the range that is close enough to being in focus that things appear sharp. It is still not a good substitute for critical focusing.

Having said all that, please try Google for more information. A lot has been written on this subject. However you will not find "the perfect lens", because it simply doesn't exist, except in CG. A lens with a very small aperture opening will give you great DOF, but you'll need to be shooting in bright sun to get enough light for your shot!

oakstreetphotovideo
05-17-2008, 10:26 AM
One more side note, related to #3 ... #3 means the cheaper the camera you buy, the more DOF you're going to have. For most film makers, that is considered a bad thing, but for you, you're in luck; spend less and get more! (inexpensive cameras often have 1/4 inch CCDs).

oakstreetphotovideo
05-17-2008, 10:27 AM
Another thought about #3 ; rather than spending $15,000 on another lens, spend $300 on a cheap camera for those shots where you want huge DOF!

Filmmaker516
05-17-2008, 10:54 AM
Well, I'm not sure if this is going to help or not, but have you tried a .7x wide angle? There is a lot less distortion and closeups are still achievable.

Hope I could help,
Steve :cool:

oakstreetphotovideo
05-17-2008, 11:37 AM
The reason that focal length doesn't technically affect DOF is because, even though a telephoto lens has less DOF at the same distance, you must back away from your subject further to get the same framing as you go with the wide angle (which increases DOF). The reverse is also true if you go wider. DOF increases at the same focal distance, but you must now move in closer to get the same framing, thereby negating the affect, as moving closer decreases DOF.

oakstreetphotovideo
05-17-2008, 11:44 AM
Furthermore ...

Wide angle lenses affect the image in ways that are often unflattering. If you're trying to make someone look like a giant, a low angle combined with a wide angle lens is perfect, but if you want natural looking shots, you really want to lean towards medium telephoto.

If you need to get a specific framing, which you do for most shots, the only way you will really affect DOF with with aperture (iris) setting and camera selection. If you shooting HD and delivering in SD, you could back further away and crop (which achieves the same affect as having a smaller CCD, because you are using just a portion of your sensor area).

The selection of a wide angle, normal, or wide angle focal length should be based on other factors than DOF, because they will affect the wideness and depth of your image. e.g. If you want to make it look like someone is running down a very long stretch of highway, a wide angle lens will make the highway look longer, whereas a long (telephoto) lens will make it look shorter. Those are the things you should be thinking of when selecting lenses. Of course you've got practical considerations if you are shooting in a small room, but that's just making due with what you have.

Don't shoot yourself in the foot to overcome a problem that can be overcome with creative shooting techniques and practice.

Doug