Why?? What would you need 64 seconds for?

If 32 seconds is a stop underexposed. :rolleyes:

Seriously, there are a lot of situations that long shutter speeds are used. Like dark interiors with small apertures (for maximum depth of field) and night time skyline shots. Any specifics on why you're asking? And is it film or digital - it makes a difference because film has a reciprocity failure that needs to be taken into account.

If you're questioning why 64 instead of 60, did you ever notice the shutter speeds on the dial aren't always half or double of the one they're to? For example, 1/60 then 1/125 - or 1/8 and 1/15? It's just easier than saying 1/62.5 or 1/7.5, etc. If your camera has a 30 second shutter speed, it's probably open for 32 seconds - 60 for 64.

The reson i am asking is beacuse i experimented with the 64 second exposure at both ends of the aperture extreme, and all shots were overexposed. the photos were attempts of night cityscapes.

The particular camera is digital.

You still have to meter the light, whether it's at night or during the day. Apparently it wasn't dark enough to use that shutter speed at any aperture.

Two factors increase noise on digital shots - long shutter speeds and high ISO settings. In my experience - at least with my cameras - I have better luck with longer shutter speeds, and stick with the lowest ISO you've got.

Think about it like this Payn..

A proper expose is like a bucket properly filled with water (water being the light). There are three variables in filling the bucket. How far is your faucet open? (aperture) How long are you holding the bucket under the faucet? (Shutter speed) and What size bucket do you have? (The smaller the bucket, the higher the iso). A perfect combination of these will lead to a perfect exposure. If the flow rate of your water is very slow (either because of a small aperture or little available light) you need to use both or either of the other two options including slow shutter speeds to get a proper exposure.

Why?? What would you need 64 seconds for?
THIS is exactly the cool reason you'd need it! Ohhh, the fun you can have with it!

http://bizfx.com/darkness/3sidebw.jpg

i wonder if digital sensors suffer reciprocity effect

i wonder if digital sensors suffer reciprocity effect

They don't. However, underexposed areas or overexposed areas that are "corrected" in post might shift in color due to clipped color channels. But there is no such thing as reciprocity in how it affects color and exposure at longer exposure times.