What ND filter is needed, please?

[EyeDocPhotog]

I finally have a few hours to myself this weekend (read: no on-call, yard work or attempts at home repairs :-)) so I’m planning to shoot a few long exposure daytime scenes in a park near me. I have some experience in long exposure night shots, but as for daytime…. well, my knowledge ends with a basic understanding of ND filters.

I will be shooting in a very bright area, albeit during magic hour, and my Seikonic light meter has already “warned me” that at F36 and ISO 100 I would still need 1/10 Tv, which is way too fast for what I’m trying to accomplish. So an ND filter to the rescue, but which notation? ND8, or 16, 32 or beyond?

The light meter, for all of its advancements, does not give me the option of settings for ND filters. Is it just trial and error? I understand that for each f-stop, the % transmitted light is decreased by 1/2, but I also know there is no formula for “Time of day(X) times given shutter (Y) = Theorotical aperture (Z).”

Can anyone shed some light here, pun intended? 🙂

[cameraclicker]

I don’t do a lot with an ND filter, so I only have one.  It is adjustable.  The advantages are it takes less space in the bag and you can adjust it to a low density value so you can see to focus, then adjust it to a greater density for the photo.  I suspect dedicated density filters actually do a better job, but for playing around the variable one is enough.

A stop is half or twice the light.  Half or double shutter speed, half or double ISO, or adjust aperture.

 

Here is a link to a discussion about ND filters:  http://www.picturecorrect.com/tips/neutral-density-filter-tips/

 

Have to run.  Hope this is enough to get you started.

[EyeDocPhotog]

Thanks a whole bunch. The article was very helpful.

You know, I re-read what I was saying about f-stops and shutter speed and I came to realize that I had KNOWN this information all along, but because of aperture priority and shutter priority modes, my mind doesn’t have to make that calculation any longer. Indeed, even through the viewfinder on Manual mode, there is an exposure meter which will let me know if I am over/underexposed, and I’ll just flip whichever dial to center it, and bingo! Properly exposed shots.

As with anything, it’s the fundamentals which must be reviewed time and again.

Thanks again for the help!! 🙂

[nesgran]

I would think a 6-stop ND filter would be reasonable unless you are going for really really long exposures. f36 is generally a bit excessive unless you need a monster depth of field with a longer lens but for usual landscape lenses f22 or even f16 will be plenty and will give you better image quality as there is less diffraction. 6 stops should give you a 6 second exposure at f36, 3.2s with f22. If you can drop down to iso 50 even better but if you want f11 or f16 a 10 stop would probably be a better idea. You may find that the calculated shutter speed doesn’t match what makes for a good photo though and you may need to underexpose/overexpose accordingly. Shoot in raw if don’t normally as most ND filters, even B+W ones, come with a colour cast so use a grey card and correct afterwards

[EyeDocPhotog]

Thanks, nesgran, I did purchase a 10 stop ND. Between your and CC’s , I’ve received quite the education on ND filters.

You know, again, it’s all about the basics.

*** BTW: How do you reference a quote from someone’s post and have it highlighted in YOUR own post? I see many of you do this, and I haven’t yet caught on the technique.***

[cameraclicker]

*** BTW: How do you reference a quote from someone’s post and have it highlighted in YOUR own post? I see many of you do this, and I haven’t yet caught on the technique.***

Usually I copy what I want to quote and paste it into the reply window.  Then I add my own text on the next line.  And, finally I go back and highlight what I pasted, then click the toolbar quotation marks icon (or b-quote if in text mode).

 

[EyeDocPhotog]

Usually I copy what I want to quote and paste it into the reply window.  Then I add my own text on the next line.  And, finally I go back and highlight what I pasted, then click the toolbar quotation marks icon (or b-quote if in text mode)

Is that it?! See, I haven’t been missing as much as I thought. I can even change the text color! Man, I’m starting to feel like my parents when I showed them the internet for the first time…. 🙂

[EyeDocPhotog]

Actually, can only change the text color during edit mode, after posting it shows up black…. oh, well, I’m happy with the indentation.

[Bill]

EyeDoc, I know this sounds way to obvious, but often overlooked for long exposures. Make sure your lens and filter are 100% spotless, or you’ll be removing spots in post. It happens all the time, but more dramatic due to the extended exposure time.

The thing to watch for also is the angle of the sun compared to the position to the ND filter if you are shooting in high-noon or broad daylight time. The cheap variable ND’s tens to create some cross-hatching effects when the sun is at certain angles in comparison to the front element of the filter.

Give the 10-stop a try, you may be surprised to see that even with a very small aperture, it can still let in a lot of light. I shot a skyline once using a B+W 10 stop and a Lee .9 Graduated ND at ISO 400 f/14 for 30″ turned out great.
The reason why such a need for so dark of a filter was the sun was reflecting off of a glass high-rise onto a Bay, basically double reflection.

Good Luck!

[EyeDocPhotog]

Bill, thanks for the not-so-obvious tip! I learned about sensor cleaning after shooting the moon at midday, only to see the dust spots from my sensor at f32 which, of course, were not present below ~f16 due to diffraction limits. I will remember to clean the filter with my lens pen before hand.

I will also play with the angles too for your reasons stated. I’m sure this 15″ shot is going to take all afternoon for the setup. But I am looking forward to it. 🙂

[nesgran]

it is only variable NDs that suffers with angles as they are essentially two circular polarisers stacked on top of each other

[EyeDocPhotog]

it is only variable NDs that suffers with angles as they are essentially two circular polarisers stacked on top of each other

 

Yup, kinda figured that was the case. The only way to produce variable degrees of light transmittance diffusely through the entire lens is with 2 opposing polarizing filters.

[Author]

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