The correct exposure time with ND filter

ND filters (also known as neutral density filters or neutral density filters) have the property of absorbing part of the incident light and thereby adjusting the exposure time in order to realize a picture with the desired exposure time. It is precisely this property that makes the gray filter so unique and at the same time irreplaceable, since this effect can hardly be achieved in digital post-processing. The merging of different recordings, i.e. the attempt to artificially simulate a long exposure, almost always shows the problem of possible artefacts. These problems do not occur when using an ND filter. In addition, with a neutral density filter, you only have to take one shot to get the desired result immediately.

How do you calculate the correct exposure times with an ND filter?

Don't worry, you don't need to be a math pro! For example, you can simply use our conversion table or one of the various apps. But if you prefer to use a clear table when taking pictures, or if you prefer to learn how to calculate the shutter speed with ND filters, this guide is just the right thing! Below we have shown a conversion table of recording times with ND filters for you. If you would like to learn more about neutral density filters in general, we recommend our FAQ article. If you only want to work with one table, you can simply skip the next paragraph.

Read also:

All about ND filters

When should you use ND filters

Landscape photography with ND filters

In order to gain a general understanding, it is important to know by how many stops an ND filter darkens. The different strengths of the filters indicate by how many apertures they reduce the light. For example, an ND8 filter darkens by 3 f-stops, an ND1000 filter by 10. With this knowledge, you as a photographer should be able to understand the following calculation more easily.

Calculation of shutter speeds with ND filter

Calculating shutter speeds with ND filters is a simple process that requires just a few steps and should be easy for any photographer. A pocket calculator is an advantage for the procedure, but you always have it with you in the form of your cell phone. You can see the necessary steps here:

First you install all the filters, with the exception of the gray filter, in your filter holder or screw them directly onto the lens. Then you take a correctly exposed test shot and note the length of the exposure time. In our example 1/125 seconds.
Now we mount the gray filter, for example the Kase ND1000 100x150 mm, and notice that the designation is ND1000. The 1000 indicates the value by which the shutter speed must be multiplied when the filter has been mounted. Because with the filter installed, 1000 times less light hits the sensor. Therefore, the exposure time has to be increased by a factor of 1000.
If a shutter speed of a fraction of a second was output from the camera (here 1/125s), the value should be converted to seconds. So 1/125s = 0.008 seconds, i.e. 1 divided by 125.
This value is multiplied by 1000, which means 0.008s x 1000 = 8 seconds. So this is the exposure time needed to get a shot with the same exposure after attaching the ND1000 ND filter. The camera default mode will then be set to 15 seconds as that is the closest value that can be set. It would also be possible to set the exposure time to an exact exposure of 16 seconds with a timer remote control.
Now if we use an ND64 100x150mm, for example, the calculation would be 0.008s x 64 = 0.512 seconds. This gives a shutter speed of about 1/2 second.
However, these calculations can sometimes be impractical for landscape photography in nature. Our simple table can help you avoid the calculations.

ND filter table

Below is the simpler method using a conversion table. Reading it off is very simple: First, find out which ND filter you want to use. In the left column you will then find the time that you set on the camera for the test recording. In the right columns you will find the appropriate exposure time after you have installed the ND filter in front of the lens. The table can also be used the other way around, i.e. if you want to achieve a certain exposure time and you want to know which ND filter you should use for this.

ND Filter Exposure Table

Exposure times chart with different filter strengths

Exposure time without ND filter	3 Stops 0.9 ND8	4 Stops 1.2 ND16	5 Stops 1.5 ND32	6 Stops 1.8 ND64	7 Stops 2.1 ND128	8 Stops 2.4 ND256	9 Stops 2.7 ND512	10 Stops 3.0 ND1000	11 Stops 3.3 ND2000	15 Stops 4.5 ND32000
1/8000s	1/1000s	1/500s	1/250s	1/125s	1/60s	1/30s	1/15s	1/8s	1/4s	4s
1/4000s	1/500s	1/250s	1/125s	1/60s	1/30s	1/15s	1/8s	1/4s	1/2s	8s
1/2000s	1/250s	1/125s	1/60s	1/30s	1/15s	1/8s	1/4s	1/2s	1s	16s
1/1000s	1/125s	1/60s	1/30s	1/15s	1/8s	1/4s	1/2s	1s	2s	32s
1/500s	1/60s	1/30s	1/15s	1/8s	1/4s	1/2s	1s	2s	4s	1m 4s
1/250s	1/30s	1/15s	1/8s	1/4s	1/2s	1s	2s	4s	8s	2m 8s
1/125s	1/15s	1/8s	1/4s	1/2s	1s	2s	4s	8s	16s	4m 16s
1/60s	1/8s	1/4s	1/2s	1s	2s	4s	8s	16s	32s	8m 52s
1/30s	1/4s	1/2s	1s	2s	4s	8s	16s	32s	1m 6s	17m 6s
1/15s	1/2s	1s	2s	4s	8s	16s	32s	1m 6s	2m 13s	33m 20s
1/8s	1s	2s	4s	8s	16s	32s	1m 4s	2m 5s	4m 10s	1h 6m 40s
1/4s	2s	4s	8s	16s	32s	1m 4s	2m 8s	4m 10s	8m 20s	2h 13m 20s
1/2s	4s	8s	16s	32s	1m 4s	2m 8s	4m 16s	8m 20s	16m 40s	4h 26m 40s
1s	8s	16s	32s	1m 4s	2m 8s	4m 16s	8m 32s	16m 40s	33m 20s	8h 46m 40s
2s	16s	32s	1m 4s	2m 8s	4m 16s	8m 32s	17m 4s	33m 20s	1h 6m 40s	17h 23m 20s
4s	32s	1m 4s	2m 8s	4m 16s	8m 32s	17m 4s	34m 8s	1h 6m 40s	2h 13m 20s	1d 12h 24m 32s
8s	1m 4s	2m 8s	4m 16s	8m 32s	17m 4s	34m 8s	1h 4m 18s	2h 13m 20s	4h 26m 40s	3d 0h 49m 4s
15s	2m	4m	8m	16m	32m	1h 4m 18s	2h 13m	4h 26m	8h 53m	5d 16h 32m
30s	4m	8m	16m	32m	1h 4m	2h 8m 36s	4h 26m	8h 53m	17h 6m	11d 9h 4m

Which effects can be achieved with a gray filter?

The gray filter is not only used to take photos in bright sunshine. A gray filter can be used to create a wide variety of effects, such as making people disappear from busy squares. As a rule of thumb, you can remember that the darker the gray filter, the stronger the effect that is achieved. The following effects are the most common and most requested by most photographers:

When shooting architecture, you can make people disappear
Wiping effects on water or clouds
Solid light trails can be generated by moving cars

What tools do you need for long exposures with a gray filter?

Especially when photographing landscapes and buildings, an image that is not blurred is essential. The following equipment is almost mandatory so that the selected motif is represented perfectly in the photo.

Stable and not too heavy tripod
remote trigger
Correction table or a calculator for setting the exposure times

Even with a very good and stable tripod, blurring can occur in the image. This is usually not due to an insufficiently stable stand, but to the mirror lock-up of the camera. In order to create the perfect recording, it is therefore important to avoid even the slightest vibration. To achieve this, you can simply turn on the mirror lock-up on SLR cameras.

By activating the mirror preset, the mirror of the camera is already folded up before the actual picture is taken. The mirror then remains in this position. If you then press the shutter button on the camera, the shock caused by the folding up of the mirror has already happened. Then only the "curtain" of the camera is opened to carry out the exposure, which means that the folding of the mirror can no longer have a negative effect on the image.

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