Camera Labs

[jake.rohan]

ok. what i want to be able to do, is to take long exposures (20 minutes-ish).

I'm sure you can get filters that just reduce the light entering the camera, but i cant find out what they are called, or information regarding how many i will need for different lighting conditions.

any help will be appreciated.
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[Alex_Venom]

Why do you need that? If you want to reduce the amount of light, you can just close the aperture and low the ISO.
If you get f/22 at ISO 100 it will get pretty dark!
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[Adi Zulhusni MarkII]

@ Jake

Are you taking the Bulb Mode Exposure during the daylight or nighttime ?

Yep Alex was right you need to small the aperture setting like f/22 & use 100 ISO

I been try the Bulb Mode Exposure just small the aperture setting during the night & it work ! BUT it over blown because I forgot to set the ISO to ISO 100 by that time I was using Auto ISO( Which is ISO 800! )
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[JakeOConnell]

They're called ND (neutral Density) filters, the higher the number next to them, the darker they are (ex nd-8 is darker than nd-4)

They sell things called ND-grads, in which the top is fully solid that color gray, then it slowly fades down, these could help keep the sky exposed correctly for the rest of your photo.
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[jake.rohan]

[ABHIJIT]

What are you going to shoot for 20 mints exposure? I am very sure ND filter is not solution to reduce light just because you want to do 20 mint exposure shot. If you are shooting sky at night for 20 mint, then you can get done just by selecting narrow aperture. Also during day, if you are going to do 20 mints exposure, it will over-expose photo no matter what. ND filters are used in specific situations during day time, when you want little slower shutter speed.

From wiki:

[popo]

The big problem with a small aperture is you're forced into a deep DoF, and also you will be in diffraction softening. Using ND instead means you can keep the aperture fairly wide for sharpness and have a shallow DoF if you want.

One other possible alternative. Take several shorter exposures and average the results.
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[calmac1991]

As already said, you'll need an ND (neutral density) filter. I wouldn't recommend going down to f/22 because it will reduce image quality because of diffraction.

Here is a list of how many stops each ND filter will reduce the light by:

ND2 reduces by 1 stop (requires shutter speed 2x as long)
ND4 reduces by 2 stops (requires shutter speed 4x as long)
ND8 reduces by 3 stops (requires shutter speed 8x as long)
ND16 reduces by 4 stops (requires shutter speed 16x as long)
ND1000 (should actually be 1024, but usually isn't) reduces by 10 stops (requires shutter speed 1024x as long)

On an overcast day, assuming that the correct exposure would be 1/60 at f/11, an ND1000 filter would allow for a 15" to 20" exposure at f/11 or around a minute at f/22 (which I don't recommend). You'll find it difficult to get an exposure of a minute on an overcast day, never mind twenty! As far as I know, the ND1000 filter is the strongest available.

Shooting at dusk or night time is another way to get much longer exposures (especially if you also use an ND filter).

Another option, would be to by an ND1000 filter plus another and use them at the same time. You add the number of stops together, so if you used an ND1000 (10 stops) with an ND16 (4 stops), it would total 14 stops, which allows a shutter speed 16384 times slower, which would turn the 1/60 into around 5 minutes.

Be warned that while ND filters are expensive and the similar "grey" or "gray" filters are much cheaper, NEVER get the "grey" filters because they tend to have a colour cast which will severely affect your images, especially with darker filters, unless of course you plan to convert to black and white.

However, exposure times of 15" to 20" achieved with the ND1000 alone should be long enough for most long exposure effects, such as long exposures of the sea etc. to get that strange David Burdeny-esque "misty" look to the water.

I hope I have helped! (I think the calculations are correct, but it's possible I have made mistakes).
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[jake.rohan]

yeah. thanks.

it was mostly for Sea shots and for sunset shots.

all the information has been heaps helpful. thanks.
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No guts, no glory
Canon 50D, Canon 50mm f/1.4, Canon 100-300 f/4.5-5.6, Sigma 24-60 f/2.8, canon 430EX II, Cactus v4 triggers
1970 Konica Autoreflex T, 135mm f/3.2, 52mm f/1.8, 35mm f/2.8, Konica 2x teleconverter

Wishlist: Canon 70-200 f2.8L IS USM

Flickr

[JakeOConnell]

hey,,, you can stack filters, so like 5 ND 1000's =s a nd 5000 right?



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Jake O'Connell, 40D Crew
Canon EOS 40D | 28-135mm IS | 50mm f/1.8 |Vivitar DF 383 | Vivitar 285hv
My Flickr
my Blog
"Photography isn't so much about the results as it is the collective experience, your interactions with people and with the world"

[calmac1991]