Night/extreme lowlight Photography (C & C and hints?)

[rhett7660]

genshi

Love the last picture in the series. Excellent shot IMHO..

 

[genshi]

genshi

Love the last picture in the series. Excellent shot IMHO..

Thank you! I'm kind of partial to that one as well (people tell me it looks like an alien face.)

 

[compuwar]

Actually the only thing that isn't logical is the fact that big apertures have small numbers, and small apertures big numbers. It's a hangover from film-based photography...

It's got nothing to do with film, so it's not a "hangover." It's because the aperture is a ratio of the focal length and the effective aperture diameter. This allows the direct correlation of the amount of light let in by two lenses of differing focal lengths. The f-number is the ratio, for example, if the focal length is 4 times the pupil diameter, the f-number is f/4. The value f/N is literally "Focal length divided by N" for the diameter of the lens's aperture.

A 100 mm lens with an aperture setting of f/4 will have a pupil diameter of 25 mm. A 135 mm lens with a setting of f/4 will have a pupil diameter of about 33.8 mm. The 135 mm lens' f/4 opening is larger than that of the 100 mm lens but both will produce the same amount of light at the focal plane.

Paul

 

[maddagascar]

It's pretty logical... Make your finger and thumb into a circle; this is the aperture of your camera. To let more light through this hole, you can either make it bigger or increase the amount of time it's 'open'. Less light: smaller hole or less time open. It's juggling these two variables that allows you to get everything in focus, from a few feet to infinity (f11, say), or just a tiny part of the pic in focus (say f1.8).

With a tripod you have total control over how your pic will look. You don't have to fret that your lens isn't fast enough, etc. Actually the only thing that isn't logical is the fact that big apertures have small numbers, and small apertures big numbers. It's a hangover from film-based photography...

I 'guesstimate' the exposure (something that would have been rather expensive in the days of film...), and make adjustments from there, based on what I see on the back of the camera. Keeping everything 'manual' means you get a 'feel' for light (quality and quantity). If you let the camera make all the decisions, you don't get this extra control or 'feel'...

how do you get to focus on things from a few feet to infinity? i've been reading about far you can focus, but i don't have anything on my lens to switch up adjustments like that. it is still a lens kit.

 

[compuwar]

how do you get to focus on things from a few feet to infinity? i've been reading about far you can focus, but i don't have anything on my lens to switch up adjustments like that. it is still a lens kit.

Google "Hyperfocal distance" or "DoF calculator."

 

[flosseR]

It's got nothing to do with film, so it's not a "hangover." It's because the aperture is a ratio of the focal length and the effective aperture diameter. This allows the direct correlation of the amount of light let in by two lenses of differing focal lengths. The f-number is the ratio, for example, if the focal length is 4 times the pupil diameter, the f-number is f/4. The value f/N is literally "Focal length divided by N" for the diameter of the lens's aperture.

A 100 mm lens with an aperture setting of f/4 will have a pupil diameter of 25 mm. A 135 mm lens with a setting of f/4 will have a pupil diameter of about 33.8 mm. The 135 mm lens' f/4 opening is larger than that of the 100 mm lens but both will produce the same amount of light at the focal plane.

Paul

Compuwar now you outdone yourself. that was the simplest and most striaght forward explanation I have read on Aperture.
Excellent!

 

[rhett7660]

It's got nothing to do with film, so it's not a "hangover." It's because the aperture is a ratio of the focal length and the effective aperture diameter. This allows the direct correlation of the amount of light let in by two lenses of differing focal lengths. The f-number is the ratio, for example, if the focal length is 4 times the pupil diameter, the f-number is f/4. The value f/N is literally "Focal length divided by N" for the diameter of the lens's aperture.

A 100 mm lens with an aperture setting of f/4 will have a pupil diameter of 25 mm. A 135 mm lens with a setting of f/4 will have a pupil diameter of about 33.8 mm. The 135 mm lens' f/4 opening is larger than that of the 100 mm lens but both will produce the same amount of light at the focal plane.

Paul

How is this possible? I know the answer is staring me right in the face but it is not making sense to me. You have a larger diameter so how would the same amount of light be produced? Are you saying respectively they produce the same amount of light?

 

[compuwar]

How is this possible? I know the answer is staring me right in the face but it is not making sense to me. You have a larger diameter so how would the same amount of light be produced? Are you saying respectively they produce the same amount of light?

Yes, the same amount of light- it's basic physics. It's probably easier to see using 100mm and 200mm. So, 100/4 is 25 and 200/4 is 50. We know that light follows the basic rule that its intensity decreases linearly with an increase in distance and visa-versa (the inverse square law.) So, light that has to travel 100mm is twice as bright as light that has to travel twice as far, in this case- 200mm. So, to get the same amount of light, you need to double how much light there is- 50mm instead of 25mm of diaphragm.

This is why lenses and lens elements get larger (and hence more expensive) as we increase their light-gathering abilities. We have to get more light through the larger aperture (in focus) so that takes larger elements to go with the larger diaphragms.


Paul

 

[rhett7660]

Yes, the same amount of light- it's basic physics. It's probably easier to see using 100mm and 200mm. So, 100/4 is 25 and 200/4 is 50. We know that light follows the basic rule that its intensity decreases linearly with an increase in distance and visa-versa (the inverse square law.) So, light that has to travel 100mm is twice as bright as light that has to travel twice as far, in this case- 200mm. So, to get the same amount of light, you need to double how much light there is- 50mm instead of 25mm of diaphragm.

This is why lenses and lens elements get larger (and hence more expensive) as we increase their light-gathering abilities. We have to get more light through the larger aperture (in focus) so that takes larger elements to go with the larger diaphragms.


Paul

Ahhhh yes it was much easier to see when using the 100mm and 200mm. Thank you for the explanation.

 

[maddagascar]

soo if you had to take a night picture with a person in the foreground and the city landscape as a back ground, would you just use flash and a longer shutter speed?

i mean, i still get confused on when changing the F-stop, someone in a another thread, maybe this one said only to use a low F/stop for people in motion..but then read it was good for night shots since it can take in more light.

soo i mean, any tips on those type of shots? would you want to use the flash and immediately have the person move to take in the back ground scenery, or do you have to tell him to stay perfectly still..lol

also, for putting it in "BULB" mode, is it bad if you leave it there for a long time, like for a star trail or something? just didn't want to start a new thread for these questions.

and what does it mean to have a "fast" lens..lol..always wondered.

this is an image i saw in another thread, i like how this person got the train with a trailing light effect, but got the people still. like if they moved, wouldn't it have been blurry? can anyone tell me how this simple photo was achieved?