Determining exposure with long shutter speeds

[tony868]

Hello all. I'm heading out on a much needed vacation to the beach in a week and would like to try my hand at some landscape shots. I'd love to get some sunrise/dusk shots among other things. I have a tripod and cable release for long exposures but what is the best way to determine how long to keep the shutter open? Is this mainly a trial and error situation or are there guidelines to use? Thanks for any help! BTW, I'm shooting film, not digital, in case that makes a difference.

[another view]

Tony, determining exposures in low light is just like determining exposure in any other kind of light. I usually shoot in manual mode and use a spot meter in cases like this. A spot meter takes some time to master (which I'm not going to say I've mastered it yet!) but it's a very useful tool and well worth the effort. Save this practice for a time other than vacation, other than maybe a couple of shots after you've taken your shot the way you usually work.

The first thing to do, even before taking the camera out of the bag, is to figure out what you want to shoot. I'm really not trying to be too basic here, sounds like you have been shooting for a little while anyway, but this is important of course. Then figure out how you want to shoot it. Long shutter speeds give an effect and let's say that this is the effect that you want. If you have an SLR camera with a built-in light meter and has manual control, this is a good time to use it. Set the shutter speed on what you would guess that you want to use, then adjust the aperture until the light meter tells you that you have the correct exposure. Maybe you've selected a shutter speed too slow for even the smallest aperture to give you a proper reading - in that case, pick a faster speed. Exposure is an equation - changing one of the three variables will affect the others. The three variables are shutter speed, aperture and ISO (film speed). I generally don't often use the smallest aperture that a lens has because it's usually not the sharpest setting. Usually one or two stops open from the smallest aperture will be very good though.

Couple of other things - if you want slower shutter speeds than you can get, you have several options. Wait until the light level is lower, but the look will be different too. Use a ND (Neutral Density) filter which is like sunglasses for a camera lens. Common ND filters are two or three stops but others are available too - or use a polarizer which can help too. Another option is to use a slower film, but that's not always convenient.

One thing to be aware of is reciprocity failure. Tell me what film you plan to use and I'll explain it...

[Ronnoco]

Well the simple approach is about 1/60 sec. at about f. 2.8 handheld. To get fancier, it is a tripod with a neutral density filter to tone down the exposure for the bright sky and bring up the detail in the foreground. You might want to even experiment with both a polarizer and a neutral density filter. Adjusting colour balance and using flash in a very careful precise manner can also add some detail in the foreground without making it look unnatural. Depth of field may be a challenge if you also want to include a foreground branch or other frame, but if absolutely necessary it is still possible to post process the depth of field.

Ronnoco

[another view]

Well the simple approach is about 1/60 sec. at about f. 2.8 handheld.

How do you come up with an exposure without knowing about the light level or film speed being used?

[Loupey]

AV summed it up pretty good in his original reply.

I would just like to add that your camera's built-in meter always tries to make everything a neutral gray (18% gray). To keep things simple, once you have framed the shot you want, look within it and pick out an area you want to be neutral. Meter on that. Recompose and shoot.

Determining exposure is easy if you keep it simple and especially if you shoot in manual mode. When I head out to shoot wildlife, I meter on grass when I first step out of the truck then lock it in at that setting and shoot the whole day with it (as long as the subject is in the same light ).

Hope that helps.

[tony868]

Thanks for all the good advice! I haven't ventured into manual mode yet so I'll have to practice a little first. As I am looking through books and see people using exposure times that are several seconds (or even minutes) long, are they most likely using light meters to figure that out?
AV, not sure what kind of film I'm going to use yet. Most likely it will be color negative film in the 200 range.
Thanks again...these boards are very helpful for a beginner like myself!

[another view]

As I am looking through books and see people using exposure times that are several seconds (or even minutes) long, are they most likely using light meters to figure that out?

Absolutely. The light meter is a tool for you to determine the exposure that you want. Using a spot meter and working with the camera on manual mode is the way I like to do it, but it's not the only way. You may be looking at some shots taken with a very slow film like Fuji Velvia slide film (the original ISO50 speed, which may not be made anymore). A lot of times I exposed that film at ISO40, and with reciprocity failure, an aperture of about f11 and a fairly low light level you can easily get a shutter speed of several seconds or more.

Basically, reciprocity failure is where the film needs more exposure due to using a slow shutter speed. With most films, at 1/30 or faster you don't have to worry about it and it's actually a pretty minor thing anyway. If you were using Velvia at 1/8 sec then you might have to add in 1/3 stop which is a slightly longer shutter speed. With color neg film I usually overexpose by 2/3 stop anyway because the negs come out better (my opinion) so you really shouldn't need to worry about this anyway. For ISO200 film, that would mean setting the camera for a film speed of ISO125. Hope I'm not losing you here - there are some weird concepts I've been bringing up - but they are all part of the craft!

[Ronnoco]

How do you come up with an exposure without knowing about the light level or film speed being used?

Oops! I should have added ISO 100.

Ronnoco

[another view]

Oops! I should have added ISO 100.

Ronnoco

Tony, I'm going to take this as an attempt at humor. You will need to use a light meter to determine exposure. One thing to be careful of when shooting manual is not re-checking your exposure from time to time. When the sun goes behind a cloud, suddenly your light level changed a lot...

Truthfully, some street photographers don't use a light meter; or at least not often. They've shot a ton of film and can guess exposure by looking at it. Usually these photographers use B&W film which can have more latitude (margin of error, basically) so even if they're off a little it's not much of a problem. In that type of shooting, I'd say that getting the composition is much more important than having a technically perfect print - but some street shooters are really good in the darkroom too. With landscape work, you will have time to properly meter the scene so by all means take the time to do it.