What ND filter should I choose?
If you want to try shooting with one ND filter and at slow shutter speed for the first time, the best choice for now would be a high versatility ND filter, like a ND8 or ND16. As their ND value is not high, these filters are easy to use and suitable for beginners.
Can I leave my protector filter on the lens when using ND filters?
No. Before attaching a ND filter, make sure to remove any protector filter from your lens. Stacking up two filters may cause vignetting (black corners on the final image). Also, flare is more likely to occur with two filter glasses overlapped.
Exposure measurements are so hard! Is there any easy way to calculate it?
Recently dedicated smart phone apps can calculate what will be the shutter speed when using ND filters. Dedicated apps are OK.
Is a tripod that necessary?
Except for panning and snaps, yes, a tripod is a necessary tool in slow shutter photography. Make sure to choose one you find stable and robust. A cable release will be also necessary to further prevent unwanted shaking and to control timing when releasing the shutter. Tripod is necessary!
What is the correct order when stacking up two ND filters?
As a general rule, the ND filter with the higher density value goes on the outside, toward the shooting object. Before unwanted reflections occur in between the two filters, front ND filter will decrease the amount of light, that will cause that reflections. Higher ND outside!
How to set a shutter speed faster than 30 sec?
Camera settings allow setting shutter speed up to max. 30 sec. For faster shutter speed, select "bulb" (B) mode; then, with the help of a cable release, leave the shutter open for all the time you decided for your exposure time. For more accurate measurements, a cable release with timer incorporated is particularly helpful. Cable release is necessary!
Are ND filters necessary when taking videos with DSLR cameras?
When shooting video, a proper shutter speed needs to be set according to the frame rate (fps) value. (It usually equals to double the frame rate). If the shutter speed is too fast, the video images will appear unnaturally disconnected. So, the answer to this question is: Yes, ND filters are necessary for smooth and natural video footages.
Any tips to deeply understand slow shutter photography?
Whenever a photo from photography dedicated magazines, websites, SNS etc. drags your attention for its beauty and awesomeness, remember to pay attention to those data (shutter speed, aperture, ISO settings) usually reported below the image. As you keep taking your own photos while checking data from other photos, you will eventually master slow shutter photography and find your own style.