which lense is capable to take low light photography- f1.2 or 1.4 or 1.8 orf2?

Interestingly enough, without knowing your intentions, ANY aperture is suitable for low light photography depending on duration of exposure, subject or purpose.

If you are planning to photograph people in a dimly lit room that's one thing but, if photographing a pre-dawn glow in the sky, you actually might want a longer exposure so it wouldn't really matter how large the aperture was under those conditions (within reason, of course - this said to satisfy my #1 critic who will jump on everything I say from now until eternity... LOL).

The marks you are referring too are aperture opening sizes. The lower the number (closer it is to 1) the wider the aperture opening and therefore the more light allowed to pass through towards the film or sensor in the camera. This equates directly to the length of your exposure time. Let's just say for an example you have ISO 400 FILM and can get a 1/2 second exposure for f/1.8 and you need to hand-hold the shot. Holding a camera still for 1/2 second is physically impossible for 99% of the living people on this planet. If you had the option to switch out your f/1.8 lens for a f/1.4 lens, you could change your exposure to 1/4th second (twice the speed of the f/1.8) or 1/8th second with the f/1.2 lens. 1/8th second would be desirable under those conditions, wouldn't it?

Of course, the price rises exponentially in an inverse proportion too... you are going to get a slightly faster lens in the f/1.4 for nearly twice the price of the f/1.8 and probably closer to three times or four times the price for a f/1.2 so economics does come into play too... can you afford it and, is it worth it for what you want to do with the lens?

Bottom line is that you need to decide (and photography is making decisions) what is the purpose of your purchase and is it really necessary to accomplish your goals in the field.

I can get that same result by push processing two stops, the 400 ISO film and shooting it as if it was 1600 speed film.

Decisions, decisions.

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Those are the largest aperture setting of the lens. The larger the aperture, the more light the lens gathers and 'delivers' to the film or sensor. An f/1.2 lens allows more light to reach the film/sensor than the others listest. The fastest production lens currently available is the 50mm f0.95 Noctilux for the Leica M cameras. It allows more than twice the amount of light to reach the folm/sensor than an f1.4 lens does.

Quite simply, the smaller the f number, the wider is the aperture, and therefore it lets in more light.

This is a photograph of an old lens of mine with the lenses removed so you can see the aperture (iris diapgram) quite clearly.

The f number is simply the focal length of the lens divided by the diameter of the aperture, so if you have a 'standard' lens of say 50mm focal length, f2 would make the diameter of the aperture 25mm. so you can see that the smaller the f number, the larger the diameter and vice versa.

Although only 1/2 stop faster than f1.4 the f1.2 would be the best but its prohibitively expensive so settle for the f1.4.

Actually, if you think about it, the Leica Noctilux-M 50mm f0.95 (yes, zero point nine-five) ASPH at a cost of $9,995.00 makes the Canon 50mm f1.2 at $1,549.00 seem reasonable and the Nikon 50mm f1.2 at $699.95 downright cheap.

Buy the 50mm f1.4 and enjoy your low-light adventures.

Check out the section explaining "INFLUENCE OF LENS APERTURE OR F-NUMBER"

http://www.cambridgeincolour.com/tutorials/camera-...