20D Bulb exposure & metering

[Raj]

From what I know, if I choose bulb as shutter speed in Tv, shutter will be open for as long as I keep the shutter release pressed. That means my exposure time is not fixed.
So question is, in such case how do I meter such shots, i.e. lets say how do I make sure I wont over/under expose the shot ? Is it trail en error or there is some method to check this beforehand.

Thanks for your help

[robertwgross]

Try M mode.

The camera will show you the suggested metering, and you adjust it to suit yourself.

---Bob Gross---

[tim]

The only time I used bulb mode was when I was shooting fireworks. For that I used M mode, and trial and error for metering, since it's hard to meter things that change so frequently and vary so much.

Aside: I ended up with the rather ridiculous settings of ISO 400, F32, and exposures from 1-4 seconds - my only excuse for not using a larger aperture and a lower ISO is that I was drunk at the time!

[PacAce]

Try M mode.

The camera will show you the suggested metering, and you adjust it to suit yourself.

---Bob Gross---
If the exposure is going to require a shutter duration of more than a minute or two, I don't think even using the M mode is going to do any good since the camera meter will only go down to 30 seconds for the slowest shutter speed. For the shutter speed longer than a few minutes, you would have to rely on an external light meter to get acurate bulb exposure readings. And even they are limited in how long a shutter speed they will specify. For example, the Sekonic 358 and 558 both have 30 minutes as the longest shutter speed it can specify.

[robertwgross]

If the exposure is going to require a shutter duration of more than a minute or two, I don't think even using the M mode is going to do any good since the camera meter will only go down to 30 seconds for the slowest shutter speed. For the shutter speed longer than a few minutes, you would have to rely on an external light meter to get acurate bulb exposure readings.

We aren't talking about exposures that long, are we?

M mode works for up to 30 seconds, doesn't it?

---Bob Gross---

[Raj]

If the exposure is going to require a shutter duration of more than a minute or two, I don't think even using the M mode is going to do any good since the camera meter will only go down to 30 seconds for the slowest shutter speed. For the shutter speed longer than a few minutes, you would have to rely on an external light meter to get acurate bulb exposure readings. And even they are limited in how long a shutter speed they will specify. For example, the Sekonic 358 and 558 both have 30 minutes as the longest shutter speed it can specify.

Thats exactly my problem. I dont know how long my exposure will be but i expect it somewhere between 60-90 seconds, may be 120 ...

I guess I will have to stick to trail & error method in Tv or M mode. I dont have a external light meter...

[nosquare2003]

Try to use the largest aperture and observe the shutter speed. Shoot a test shot and observe the exposure, if applicable. And you can calculate the shutter speed if using a smaller aperture. Similarly, you can bump up the ISO...
(P.S. Film camera will be different but out of question here...)

[kawter2]

Aside: I ended up with the rather ridiculous settings of ISO 400, F32, and exposures from 1-4 seconds -....I was drunk at the time!


Haha reminded me of these.. (inspired by Heniken)


http://ericcotter.com/blog/images/30secs.jpg

http://ericcotter.com/blog/images/30secs02.jpg

http://ericcotter.com/blog/images/30secs03.jpg

[griff2]

my only excuse for not using a larger aperture and a lower ISO is that I was drunk at the time!

Ah yes, been there many times:mrgreen:

[PacAce]

We aren't talking about exposures that long, are we?

M mode works for up to 30 seconds, doesn't it?

---Bob Gross---
Bob, I think you need to reread the first post. He was specifically asking about using the Bulb mode, was he not? ???

[kawter2]

Ah yes, been there many times:mrgreen:


yea it sucks because you cant use drunk mode for Long Exposures :D

[Phil V]

If the exposure is going to require a shutter duration of more than a minute or two, I don't think even using the M mode is going to do any good since the camera meter will only go down to 30 seconds for the slowest shutter speed. For the shutter speed longer than a few minutes, you would have to rely on an external light meter to get acurate bulb exposure readings. And even they are limited in how long a shutter speed they will specify. For example, the Sekonic 358 and 558 both have 30 minutes as the longest shutter speed it can specify.

Yes the camera will only meter for exposures up to 30secs, but that doesn't make it useless for longer exposures, 30secs at f22 is 1min at f16, 2min f11 etc. (or even ISO changes). So you don't necessarily need an external meter for low light.

However most long exposures are for effect, ie star trails, headlight trails etc, and for these trial and error is the only way of getting exactly the shot you want.

[kawter2]

30secs at f22 is 1min at f16, 2min f11 etc. (or even ISO changes).

You might want to re-check your logic

[PacAce]

Yes the camera will only meter for exposures up to 30secs, but that doesn't make it useless for longer exposures, 30secs at f22 is 1min at f16, 2min f11 etc. (or even ISO changes). So you don't necessarily need an external meter for low light.

However most long exposures are for effect, ie star trails, headlight trails etc, and for these trial and error is the only way of getting exactly the shot you want.
First of all, I did say "If the exposure is going to require a shutter duration of more than a minute or two".

And secondly, the lowest EV that the camera meter will give would be for a shutter speed of 30" at whatever the largest aperture is, such as f/2.8 or f/1.4 or whatever. Not the smallest, like f/22 or f/32.

But, again, I think the original poster was talking about knowing how to figure out the exposure when using the Bulb setting. I don't know about everybody else but the only time I would resort to using the Bulb setting is when I know the EV I'm going to be working with is going to be lower than what the camera can handle with it's own meter. And if that's the case, to get an acurate exposure, I would need to rely on a external light meter.

[PacAce]

Thats exactly my problem. I dont know how long my exposure will be but i expect it somewhere between 60-90 seconds, may be 120 ...

I guess I will have to stick to trail & error method in Tv or M mode. I dont have a external light meter...
Unless you want to use trial and error by checking the LCD and the histogram the best way to get acurate exposure using the Bulb setting is to use an external light meter. The other method which could also work for you if you are shooting a "standard" scene or subject is to rely on EV tables which show you "typical" scenes and what their EV values are.

Here are links that feature an EV calculator or table:

http://www.robert-barrett.com/photo/exposure_calculator.html
http://www.fredparker.com/ultexp1.htm

[robertwgross]

Bob, I think you need to reread the first post. He was specifically asking about using the Bulb mode, was he not? ???

Yes, I read it. Bulb works good, and manual mode works good, for at least 30 seconds. Beyond that, I have not tried it much.

---Bob Gross---

[Phil V]

First of all, I did say "If the exposure is going to require a shutter duration of more than a minute or two".

And secondly, the lowest EV that the camera meter will give would be for a shutter speed of 30" at whatever the largest aperture is, such as f/2.8 or f/1.4 or whatever. Not the smallest, like f/22 or f/32.

But, again, I think the original poster was talking about knowing how to figure out the exposure when using the Bulb setting. I don't know about everybody else but the only time I would resort to using the Bulb setting is when I know the EV I'm going to be working with is going to be lower than what the camera can handle with it's own meter. And if that's the case, to get an acurate exposure, I would need to rely on a external light meter.

What made you think I was arguing with what you did say I was answering the original post, (I know my logic got twisted oops:o), however in the original question he never mentioned coming up against the lowest EV the camera would measure, just the longest shutter speed the mode would show.

I still stand by the advice of trial and error, because in the sort of pictures I've guessed he's talking about there isn't a reasonable 'average' light to read. no matter how sophisticated a meter is used. If my assumption is wrong, the poster needs to be more specific about the subjects he aims to capture.

[Titus213]

Raj,
Trial and error. When you think that photographs were being taken long before there were sophisticated meters available you have to wonder why it's all necessary now. It's not. It's nice, but not necessary. And with digital trial and error costs you a few minutes time. And if it's a once in a life time shot, oh well, maybe next life...:lol:

[Raj]

Everybody, thanks for your suggestions & links, appriciate this very much. I will stick to trial & error & see how it goes this weekend.

Another question, after trial & error suppose I have to stick to a particular shutter speed & f value for the effect I want to create & if this is overexposing the picture, then can I use a ND filter (in night) to control this ? Does anyone uses ND filter for night shots ?
I purchased ND just yesterday for daylight shots but havent used it yet.

[Jon]

You can use an ND filter any time you need to reduce the overall light level hitting the lens, day or night.

[PacAce]

Yes, I read it. Bulb works good, and manual mode works good, for at least 30 seconds. Beyond that, I have not tried it much.

---Bob Gross---
Bob, seems like we've been hit by a little bit of a "language barrier" in our discussion here. Please accept my apologies. You were also correct in your recommendation for using the "M" mode (depending on what camera Raj is using). It just occurred to me that a 1D series camera (which I what I am currently using as my main camera) has the Bulb setting as a separate selection whereas on the 20D, 10D and I'm sure on the DReb camera, Bulb mode is selected by setting the camera in "M" mode and setting the shutter speed to Bulb. I guess this is one reason why it helps to know what camera it is that we are talking about, eh? :)

[robertwgross]

I've spent many years working for international companies where the biggest problem was: "What the hell are they talking about?"

I've tried to put myself more into the perspective of the questioner. Once we understand the real question, often we can develop an answer sooner.

My favorite phrase to decipher was "Plus Driver." This was spoken by a Japanese man. Translated into American English, it became a Philips head screwdriver. Think about it.

---Bob Gross---

[PacAce]

I've spent many years working for international companies where the biggest problem was: "What the hell are they talking about?"

I've tried to put myself more into the perspective of the questioner. Once we understand the real question, often we can develop an answer sooner.

My favorite phrase to decipher was "Plus Driver." This was spoken by a Japanese man. Translated into American English, it became a Philips head screwdriver. Think about it.

---Bob Gross---
LOL :lol: And a regular screwdriver is know as "minus driver" or just plain "driver". :D

[robertwgross]

Then the Japanese speaker hit me with "Monkey Spanner." (?)

He had been taught in British English. To a Brit, a spanner is a wrench. So, we were talking about a monkey wrench.

---Bob Gross---