Neutral Density Filters

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The following is excerpted from the buying guide Nick provided us and I don't understand it: "[if] a 6-stop ND puts you in the 2-4 minute range, a 10-stop ND would push the exposure past 8 minutes."

Let's assume the 6-stop ND exposure lasts only 2 minutes. A 7-stop ND would add another 2 minutes beyond the 6-stop ND, totaling 4 minutes. An 8-stop ND would add another 4 minutes, totaling 8 minutes. A 9-stop ND would add another 8 minutes totaling 16 minutes and a 10-stop ND would add yet another 16 minutes, totaling 32 minutes. That's not remotely close to the 8 minutes explained in the buying guide.

There has got to be something I'm missing. What is it?
I agree with you computations. I use ND filters of a variety of strengths. I will sometimes use my free “ND Timer” app to quickly compute exposures when using the filters. The app then initiates a countdown timer for the exposure.

Glenn
 
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The buying guide is misleading. The writer may not understand the different ways ND filter strengths are quoted.
On the other hand you could argue that 32 minutes is "beyond 8 minutes".
If only all ND filter specs were written as stops.
This excellent page has a useful table half way down:
https://www.bhphotovideo.com/explora/photography/hands-on-review/a-guide-to-neutral-density-filters
Here is a portion of it:
View attachment 1686859
I don't think Graham Clark, of Breakthrough filters is confused. Here is a table from his guide (a free download) to long exposure photography:

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Remember too that ISO and aperture also contribute to the exposure time.
 
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Thanks, Nick, but I didn't see any discussion in the buying guide of variable ND filters.
In his free download, guide to long exposure photography he touches on Vari ND filters and goes on to say if you must use a Vari ND, go with the Singh Ray!
Screen Shot 2021-07-25 at 07.34.37.jpg
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This excellent page has a useful table half way down:
https://www.bhphotovideo.com/explora/photography/hands-on-review/a-guide-to-neutral-density-filters
Here is a portion of it:

Though I'm not an engineer, I follow the details enough to get thoroughly miffed :ROFLMAO: when charts are just plain wrong. Even the chart Richard provided is wrong. Notice that the heading in the column on the far right indicates the amount of light that is reduced. So, based on that inaccurate heading, one would read that a 2-stop filter reduces the light by 1/4th. Not true! The numbers in that column pertain to the fraction of light allowed into the lens compared to when not using an ND filter. If the heading was changed to "Amount of Transmission" as similar to the example of the chart Nick provided, one would accurately read that a 2-stop filter allows 1/4th the amount of light.

Surely there is a wall around here that I can bang my head against. No wonder this stuff can become so confusing.
 
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Though I'm not an engineer, I follow the details enough to get thoroughly miffed :ROFLMAO: when charts are just plain wrong. Even the chart Richard provided is wrong. Notice that the heading in the column on the far right indicates the amount of light that is reduced. So, based on that inaccurate heading, one would read that a 2-stop filter reduces the light by 1/4th. Not true! The numbers in that column pertain to the fraction of light allowed into the lens compared to when not using an ND filter. If the heading was changed to "Amount of Transmission" as similar to the example of the chart Nick provided, one would accurately read that a 2-stop filter allows 1/4th the amount of light.

Surely there is a wall around here that I can bang my head against. No wonder this stuff can become so confusing.
Café Drinking Team standing by . . . .
 
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I had a chance to read through the guide that I got from the website that Palouse recommended. I also checked the maximum exposure time for my Leica CL. It has a maximum exposure of 30 seconds. Based on that restriction, I think a 3 stop ND filter is probably the best option for me.

Any thoughts on this?
 
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I had a chance to read through the guide that I got from the website that Palouse recommended. I also checked the maximum exposure time for my Leica CL. It has a maximum exposure of 30 seconds. Based on that restriction, I think a 3 stop ND filter is probably the best option for me.

Any thoughts on this?
Nearly any camera should be able to extend exposure times by selecting the “bulb” setting for shutter speed. Bulb allows you to activate the shutter manually…you can then start and stop the exposure for any length of time. I have exposed images for 15 minutes. When doing long exposures, a cable release is recommended so that you don’t shake the camera by making contact with it directly when activating the exposure.

Glenn
 
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I found a three-year-old thread on the Leica forum indicating that the Leica CL has a maximum exposure of 30 seconds even when it is set to "T," which presumably means Time. The thread also indicates that there is no cable release. I find all of that unbelievable for a $3200 camera. Hopefully the camera's firmware has been updated to allow longer exposures.

https://www.l-camera-forum.com/topic/288174-could-bulb-mode-be-implemented-on-cl/
 
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@jbird: If you have a camera that allows longer exposures, consider using that instead of your Leica CL. If you don't have one, consider buying an inexpensive camera, perhaps a used model that is no longer being manufactured, that you could use solely for long-exposure photography. As an example, a very old, discontinued Nikon D7000 can be purchased for $300. Indeed, that model is my backup camera and I use it regularly in my makeshift studio.
 

Growltiger

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... even when it is set to "T," which presumably means Time.
Traditional meanings:
B means Bulb - you press to open, and when you release the shutter closes.
T means Time - you press and release to open. Then press and release again to close.
The point of T was so you didn't have to stand there for 10 minutes squeezing the bulb.
 
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@jbird: If you have a camera that allows longer exposures, consider using that instead of your Leica CL. If you don't have one, consider buying an inexpensive camera, perhaps a used model that is no longer being manufactured, that you could use solely for long-exposure photography. As an example, a very old, discontinued Nikon D7000 can be purchased for $300. Indeed, that model is my backup camera and I use it regularly in my makeshift studio.
I checked my D7100 specs on line. It has a maximum of 30 seconds too. I need to check the manual though there may be some other settings that allow for longer exposures.
Just because of residual health issues from the cancer, carry multiple cameras is not a viable option. Th CL is a good lightweight option for me.
The CL also does not have any external ports other than the hotshoe. The remote release is activated via the smartphone app. I have used the app on several occasions. It works well.
 
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Traditional meanings:
B means Bulb - you press to open, and when you release the shutter closes.
T means Time - you press and release to open. Then press and release again to close.
The point of T was so you didn't have to stand there for 10 minutes squeezing the bulb.
I have had film cameras in the past with the B setting on the dial. I don’t think my DSLR cameras do.
 
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I found a three-year-old thread on the Leica forum indicating that the Leica CL has a maximum exposure of 30 seconds even when it is set to "T," which presumably means Time. The thread also indicates that there is no cable release. I find all of that unbelievable for a $3200 camera. Hopefully the camera's firmware has been updated to allow longer exposures.

https://www.l-camera-forum.com/topic/288174-could-bulb-mode-be-implemented-on-cl/
I don’t care much for that site. I am a member there but a lot of the people ther are a bit full of themselves. Especially one of the moderators. This is a much friendlier and helpful community. I also like DPR’s Leica forum there is a good group of people there.
 
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I checked my D7100 specs on line. It has a maximum of 30 seconds too. I need to check the manual though there may be some other settings that allow for longer exposures.
Just because of residual health issues from the cancer, carry multiple cameras is not a viable option. Th CL is a good lightweight option for me.
The CL also does not have any external ports other than the hotshoe. The remote release is activated via the smartphone app. I have used the app on several occasions. It works well.
You need to be in Manual (M) mode to get Bulb (B) to show up:

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Just because of residual health issues from the cancer, carry multiple cameras is not a viable option.

I hope your health is improving!

Though I've never done long-exposure photography, it seems to me that most if not all of the time all of one's energy and time is dedicated to it. In that situation, you would need only one camera once you've arrived at the ideal location. If I'm right about that, an ND filter that reduces the light at least 6 stops could be a wonderful fit with your D7100 because of its Time setting using either a cable or infrared release (though I haven't checked which of those are supported by that camera).

Whatever you decide, I hope it works out well for you.
 

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