Forums > Technical Discussion > Photography advice - Tech stuff, Night shots, Long exposure and more.

Posted: 19th May 2006
I'll try to aid your quest with my knowlege. I studied photography for 4 years so I should at least know a little.

Manual Focusing: It's definately needed for night shots. If needed you can illuminate the subject with a torch to focus then turn it off for the pic. The blurryness is caused by movement which looks cool and it's how you get the trails etc. If the subject is out of focus it will just look fuzzy and you won't get the same effect.

Distance thing all depends. For stills at night I will position myself at the needed distance to get the composition but if i'm photographing action then i'll be further back (usually for safety reasons) and zoom in to get the right composition.

Aperture is the size of the hole in the lens that lets in the light. The bigger the number the less light that comes in thus longer exposures. The aperture also affects the depth of field which means that if you want your foreground and background in focus you need to use a small aperture number (such as 2) if you want only your subject in focus then use a high number (such as 22). When photographing fire performers you'll tend to find a short depth of field is best which works well with the aperture and shutterspeeds you want.

ISO is the speed oof the film (speed at which it reacts to light). A low number such as 100 needs a lot of light but also provides very crisp clean images. A high number such as 400 will allow photo's to be taken in lower light but it means the images will be more grainy. 200 is an average and as such is the ISO most used. You can also get 3200 speed film which is super grainy but allows for the absense of flash in low lit areas (stage/live music photography).

Never heard of hyperfocal length but google told me this:

The hyperfocal distance is the near distance of the photographed scene that still is in focus when the lens is focused to the infinity. The hyperfocal distance have this interesting property: when the focus is set to the hyperfocal, all the planes from half the hyperfocal distance to the infinity will be in focus. For example, if the hyperfocal distance is 2 meters, then if the lens is focused at 2 meters, the range of good focus goes from 1 meter to infinity. Focusing at the hyperfocal maximizes the range of good focus (cheap cameras with fixed focus, sometimes announced as focus free, are usually focused at the hyperfocal distance).

If you use flash in a long exposure you will get the image from the flash as well as the image from the long exposure. This technique is known as flash blur. The flash freezes the initial scene and the shutter staying open leads to the trails. Very nice effects but very experimental and can take a little bit of time to master.

Hope this all helped. I can go into more detail on some stuff but didn't wanna blab on about loads of technical jargon so early in the thread

Could somebody stop the room please... I'd like to get off

Posted: 19th May 2006
Extremely interesting- thankyou both

Posted: 19th May 2006
Thats great noodles... thankyou...

Depth of Field... this is one of those things i dont understand very well yet...

On the aperture size... I found that my best shots were coming out with the apeture set at F4.0 which i thought was the smallest size. Now that i know its the biggest it changes things a bit.. Does it follow then that shots are more likley to be over exposed if the aperture is opened up more...

Add metering to the list here aswell.. Can this be used to improve night shots and fire shots...? could you jsut hold a flame infront of the camera measure it. then measure a shadow and balance it? Have i got the whole theory arse ways?

Love is the law.

Posted: 19th May 2006
Shots are more likely to be overexposed with a wide aperture but they are also likely to be overexposed due to long shutter speeds.

With 35mm camera's and fire shots its a very hard balence to judge. I've just bought myself a nikin d50 to go with my f80 so I now have the option of film or digital.

A general rule to follow is 'the wider the aperture the shorter the depth of field'. The focal length of the lens also effects this though.
If you can get positioned in the right place you can make the fire and performer in focus but the fore and background out of focus.

I tend to find that with night shots on a 35mm camera bracketting is essential. With digital its a thousand times easier though.

Posted: 19th May 2006
Cool seye. thanks

Theres some things in there that im not sure i really under stand though.

Depth of Field = The with of the plane of focus? Does 'shorter' mean the the depth of field is thinner or is closer to you?

What kind of depth of field would you be looking for for a close up/portrait of a performer holding firetoys? As opposed to a shot that is big enough to encapusate long arm rotations?

How does Bracketing affect night shots?

Love is the law.

Posted: 19th May 2006
No problem

A long focal length and a short distance to the subject will give a short depth of field.

If you shoot with a short focal length you will find it very easy to get large ranges in focus (like in landscape photography).

The portrait shot depends on whether you want to see the background or not. If you arent bothered shhot with a short focal length as focussing on the whole subject is much easier. If you want to blur the background shoot from distance with a long focal length.

Bracketting is just taking the same picture several times with different settings (i.e. shoot with same shutter and several different appertures). It means that you can be pretty much garunteed that one will come out as you want it.

Posted: 19th May 2006
You got a couple things backwards there noodles, that or just a couple typo's that make it confusing at least..

The higher the number on the aperture the smaller the hole, f8 vs f5.6 for example. Because the hole is smaller in f8, the light is more focused coming through, thus you have a greater depth of field. Meaning you have a broader range of distance that will be in focus. But you also have to take a longer exposure to compensate, and that can cause issues for things like spinning where there is a bright light source, constantly moving about your frame.

If you want to pause the action (in normal situation, say you're shooting someone playing sports) than you need a fast f-stop, f2.8 for example, it will give you an extremely fast shot, but a relatively small depth of field. This is why you don't see many action shots with the background in focus.

Since we're talking about the f-stop, each stop (one step, 2.8, 4, 5.6, 8, 11 etc etc) represents the halving, or doubleing of light in the exposure. A 1" exposure at f-8, is equal to a 1/2" exposure at f-5.6, what you change is mostly your depth of field, the exposure will look the same if it was a still subject.

Now, depth of field, and field of view (or angle of view)are different. Depth of field refers to the range that will be in focus, while the field of view represents how much will be captured in the image. A wide angle shot with a fisheye lense, vs a tight zoomed in shot.

When they say the depth of field is shorter, it means the range is smaller. While there are limits on how close or far away you can accurately focus, it is adujstable. It is the difference between being able to focus on a person in the foreground AND background, or just one or the other.

Since the fire and performer are moving, you're going to have some problems. If you're using a flash, the further away you are (unless you have a remote flash) the less effective that flash will become, and the more you'll have to compensate with your exposure. If you want to freeze someone accurately and sharply, you'll either need to flash them, or do a short, fast, exposure. That all depends on how still they can keep themselves while spinning as well.

It is possible, to do a "long" exposure to get the trails, and pop the flash at some point during the shot to 'freeze' the spinner. You have a few options at that point depending on your camera. You can sync the flash to either the beginning, the middle, or the end of the exposure. Or with some you can strobe the flash, and essentially stop the person at multiple poses.

Since most fire pictures are more abstract, people get away without using tripods, but if you actually want things in focus and not rely on the flash to freeze things you're going to have to use a tripod of some sort. Typically among more serious photographers anything slower than 1/60" needs some sort of support to keep it from blurring.

As for the metering, cameras aren't typically designed to be able to figure out scenes like fire spinning, they get confused by extreme contrast and tend to try to wash everything out to make it semi even. It's more of a judgement call on your part if you like what the camera is spitting out or not. If you find a shutter speed that you like (since that is what is going to effect how long the trails are) than you can adjust and bracket using the f-stop. It will affect your depth of field but I don't really see that as much of an issue with fire.

Now that i've probably confused things and made it all worse I'll shut up... I hope I got all that right up there

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