Lens Overview Please
 

Hey everyone,

I'm looking at getting a 35mm adapter for my XL1s. I've been reading all the posts on here and it brings up some questions that I would love some answers on.

Now, remember, I am not an MIT graduate, so please keep the tech talk to a minimum.

!. I ain't got the foggiest clue what all the different mm sizes do. I know it has to do with distances, but how exactly? What are "example setups" for the different lenses?

2. I would like a breakdown of all the f stops. What do they actually do? What works best for what?

3. What adapter is getting the best results?

I know these are basic questions and will probably take some long responses, but I want to make sure I know what I'm needing before I rush out to spend the money.

Thanks all!

im bored so ill try to save you from the <<use the search function!!>>
1. I ain't got the foggiest clue what all the different mm sizes do. I know it has to do with distances, but how exactly? What are "example setups" for the different lenses?


50mm = to how the human eye sees things (the "standard/normal" lens)

anything with a smaller than 50 you can think of as a wide angle (the smaller the wider)

anything longer is for tighter shots (portrait shots)


2. I would like a breakdown of all the f stops. What do they actually do? What works best for what?

f stops are measurements of light.. how much light can pass through the lens. the bigger the number the more light loss you would get. The importance to you = with a 35mm adapter you will have light loss. you want something that will be as good as possible in low light situations. If you light right then you wont have this problem. Also the aperture size affects your DOF. so you want something with a smaller number.. the smaller the number the more money you're looking to fork out.
f/1.8 is good enough.. 1.4 or 1.2 are even better.


3.What adapter is getting the best results?
i cant give that info away :) just kidding.. they all have their strong and weak points. it depends on what you're looking for. it comes down to price vs quality... theres some amazing adapters out there that cost alot and there are some amzing adapters out there that cost very little in comparison. i know what adapters id be buying if i had a about $10,000 + to throw around. but i dont.. read to find out which one (or concept) you like the best..


4.I know these are basic questions and will probably take some long responses, but I want to make sure I know what I'm needing before I rush out to spend the money.

take the time to read and understand before you start spending your money.


someone correct anything ive said anything wrong

I'll add some more info to the very precise and concise post by Andrew :). I don't want to get "techie", but there are some concepts you should be familiar with.

Note: I'm not a native english speaker, so my spelling and choice of words might be awkward...

All I'm saying is better explained in millions of sites, being this one (http://www.paragon-press.com/lens/lenchart.htm), an easy one to understand :)

When you talk about lens properties, you have focal length (the 28mm, 50mm, 300mm number), and aperture (the f-stop numbers).

As Andrew says, the focal length is the distance from the lens to the film when focused at infinity. small numbers give you a wide angle and larger numbers give you a narrow angle with a very zoomed-in image.

The aperture is how much light the lens lets in. the f-number is the focal length divided by the diameter of the lens (not the outer diameter, but the diameter of the actual glass). So, f/1.2 means the aperture is huge, because there's almost no difference between the focal length and the diameter. It's (relatively) easy to get an f/1.2 aperture on a 24mm lens. If you can get that kind of aperture on a 400mm lens, you'll have a pretty expensive piece of glass. Long lenses with big aperture (small f-stop numbers) cost a lot.

Now, what you really want to know and understand is how all this affect your image.

short lenses (20mm, 24mm, 28mm, etc) gives you:
- a wide angle (more than with the naked eye)
- a lot of depth of field (everything is in focus)
- depth of image (you can clearly see what's near and what's far away, etc)

long lenses (80mm, 120mm, 300mm, etc) gives you:
- a narrow angle
- shallow depth of field
- the image looks more flat

small aperture numbers (f/1.2, f/1.4, f/1.8) gives you:
- a lot of light! you have to be careful with overexposing. great for low-light conditions.
- shallow depth of field (the difference is dramatic here).
- the lens has to be of very good quality to get an even picture (the edges of the frame tend to present chromatic aberrations and soft-focus problems)

big aperture numbers (f/8, f/12, f/22) gives you
- a very dark scene ;-). If you want to take a picture of the sun, use f/22. It'll come out ok! :D
- a lof of depth of field (things tend to be all in focus)
- Normally, images taken at f/5,6 or f/8 tend to be the best ones in terms of sharpness and quality.

These concepts, borrowed from still photography, also work for video, but you have to have something else in mind. In still photography, you'll create effects and balance out the aperture size with the shutter speed. (the time the shutter is open letting light in).

You can use a lens fully opened and a very fast shutter speed to achieve "similar" image to a closed down lens (big f-number), and a slow shutter speed. They are related concepts, as both deal with how (and how much) light hits the sensor or film.

When recording video, you don't have that kind of control over shutter speed. Normally, you'll want to work with twice your fps (1/50 for ntsc, 1/60 for pal). You can change the shutter speed to let less light in (1/100, 1/120), but you can't change it to let more light in... Otherwise you get an stroboscopic effect.

Bottom line is, you want a fast lens (fast means small f-number). 50mm f/1.8 lenses are pretty much standard because they're cheap, the focal length is considered to be that of the human eye, and they give a good depth of field and image quality (they're very good for over-the-shoulder shots, for example). Also, both Nikon and Canon versions are of the highest quality for the money.

Oh yeah, one more thing... When you see this:
24mm-80mm f/3.3-f/5.6

means you have a zoom lens (you can change the focal length from 24mm to 80mm). The two f-numbers mean that when you are at 24mm the maximum aperture is f/3.3, but when you zoom in to 80mm, the aperture decreases (gradually), down to f/5.6. For video, you want a lens that can keep the aperture (same f-number) all the way across its focal length. These lens tend to be very expensive.

The best example is probably one of the best Nikon lenses. The 28mm-70mm, f/2.8, which costs 1000+

When you only have one focal length number (50mm), you hava a "prime lens". Primes have a higher quality than zoom lenses. Which means, if you don't plan to zoom in on an shot, you should use a prime lens :). Of course, having a full array of primes (let's say... 24mm, 50mm, 80mm, 120mm and 300mm) can be both expensive and tedious to carry around...

I hope this doesn't confuse you :) I tried to summarize everything in one post, but try searching google and these forums. You'll want to become familiar with how lenses work and the technical aspects of capturing light (which this is all about).