Time-lapse speeds
Clouds moving very slowly, interval of 10 seconds.
Clouds moving normally: interval of 5 seconds.
Clouds moving very fast: interval of 3 seconds.
People walking down the street: interval of 2 seconds.
Path of the sun on a clear day, interval of 30 seconds.
Night landscapes, stars, moon, etc.: Interval of 20 to 30 seconds.
Shutter speeds for astrophotography: 500 Rule
500 / (focal length) = (shutter speed)
Full Frame Sensor with 24mm lens
500 / 24 = 20.8 - 20 seconds
APC-C Sensor with 24mm lens
500 / (24 x 1.6) = 13.02 - 13 seconds
Stacking Images
For those interested in stacking with Photoshop, here's how to do it:
Combine the separate images into one multi-layered image.
You can also combine images using a script – File > Scripts > Load Files into Stack.
Select All Layers.
(Edit > Auto-Align Layers) and select Auto as the alignment option. If Auto does not create good registration of your layers, try the Reposition option. If that fails, set all layers to the Lighting blending mode and manually align each image, this can take a bit of time but it's not too bad.
Layer > Smart Objects > Convert to Smart Object.
Layer > Smart Objects > Stack Mode and select a stack mode from the submenu. For noise reduction, use the Mean or Median, I usually use Median.
To change the rendering effect, choose a different Stack Mode from the submenu. Stack rendering is not cumulative—each render effect operates on the original image data in the stack and replaces previous effects.
Now you can stretch the histogram with your normal PS workflow
