hensil
Guru
Ankur,
Recently I have also got interested in astrophotography. According to my limited understanding Arshad is correct. The 500 rule (which is not actually a rule of physics but approximate value) is for full frame and for APS sensor it should be multiplied by 1.5. As you correctly said the focal length of a lens does not change on different size sensor but the angle of view certainly does and that is small sensor will render narrow FOV.
Also the star movement is there (earth motion) in a picture irrespective of focal length or sensor size however it is less noticed in wide angles compared to telephoto because the stars are less magnified.
To get sharp picture of stars one has to use the camera on a tracker.
Now to answer the OP's question, if you want to focus at infinity you could easily do it focusing on the moon, even auto focus. The scene you wanted to shoot, that is the mountains and lake would certainly be at infinity. If there is no light source for focusing use a torch light to light an object at 20 ft or further or place the light at that distance and focus on it.
If you want to shoot stars without noticeable trails then use the following settings
500/focal length for FX, for DX x1.5
for exposure use the following
f/1.4 - ISO 400 - 30 secs
f/2.8 - ISO 1600 - 30 secs
f/4 - ISO 3200 - 30 secs
f/5.6 - ISO 6400 - 30 secs.
If you have older camera with not good high ISO sensor you'll have to use a technique called pictures stacking using specialized software. Astrophotography do this to get deep sky photos like galaxies.
Henry
PS:If you just want to shoot landscape in the moon light, use a tripod, keep whatever aperture and use corresponding shutter speed in bulb mode.
Recently I have also got interested in astrophotography. According to my limited understanding Arshad is correct. The 500 rule (which is not actually a rule of physics but approximate value) is for full frame and for APS sensor it should be multiplied by 1.5. As you correctly said the focal length of a lens does not change on different size sensor but the angle of view certainly does and that is small sensor will render narrow FOV.
Also the star movement is there (earth motion) in a picture irrespective of focal length or sensor size however it is less noticed in wide angles compared to telephoto because the stars are less magnified.
To get sharp picture of stars one has to use the camera on a tracker.
Now to answer the OP's question, if you want to focus at infinity you could easily do it focusing on the moon, even auto focus. The scene you wanted to shoot, that is the mountains and lake would certainly be at infinity. If there is no light source for focusing use a torch light to light an object at 20 ft or further or place the light at that distance and focus on it.
If you want to shoot stars without noticeable trails then use the following settings
500/focal length for FX, for DX x1.5
for exposure use the following
f/1.4 - ISO 400 - 30 secs
f/2.8 - ISO 1600 - 30 secs
f/4 - ISO 3200 - 30 secs
f/5.6 - ISO 6400 - 30 secs.
If you have older camera with not good high ISO sensor you'll have to use a technique called pictures stacking using specialized software. Astrophotography do this to get deep sky photos like galaxies.
Henry
PS:If you just want to shoot landscape in the moon light, use a tripod, keep whatever aperture and use corresponding shutter speed in bulb mode.
