Gear Talk > Software & Accessories
Alternate uses uses for solar eclipse filters
jabbott:
--- Quote from: Drizzt321 on May 08, 2012, 08:27:23 PM ---That's a good thought.
I'm having trouble finding a Photography Solar filter film right now :( I'm trying to get ahold of some of the BAADER AstroSolar Photo film (ND 3.8 according to BAADER). Unfortunately, nobody has a sheet of the thing in stock, although supposedly a few places are going to get some more this week. I found 1 Canadian place that supposedly has some in stock (according to the online part), but I'm going to call and see if they really do, and how fast I can actually get it.
NOTE: The ND 3.8 is for Photography only, NOT for visual use, so if anyone gets some only use the LiveView or similar functionality. Get the ND 5 if you want to use it visually.
--- End quote ---
One option is to stack ND filters to reach the desired optical density. Being that the ND scale is logarithmic, it is possible to stack an ND3 and ND0.9 together to get an effective optical density of ND3.9 (~8000x light reduction). That optical density works well for solar photography when using very fast shutter speeds and strongly stopped down apertures. I definitely agree that Live View should be used to confirm framing and focus instead of the viewfinder. I will be using this technique for the May 20th eclipse as well as the upcoming solar transit of Venus on June 5th. B&H has many B+W ND3 and ND0.9 filters in stock so that is an option for folks who can't find dedicated filters. Just make sure you don't buy an ND .3 instead of an ND3. :D The added benefit of getting two separate filters is that later you can use the ND3 and ND0.9 individually for varying levels of smoothing out water and cloud movement in your photos. See more on this effect here: http://www.redbubble.com/people/peterh111/journal/4421304-the-ultimate-guide-to-neutral-density-filters
Drizzt321:
--- Quote from: jabbott on May 09, 2012, 12:15:11 AM ---
--- Quote from: Drizzt321 on May 08, 2012, 08:27:23 PM ---That's a good thought.
I'm having trouble finding a Photography Solar filter film right now :( I'm trying to get ahold of some of the BAADER AstroSolar Photo film (ND 3.8 according to BAADER). Unfortunately, nobody has a sheet of the thing in stock, although supposedly a few places are going to get some more this week. I found 1 Canadian place that supposedly has some in stock (according to the online part), but I'm going to call and see if they really do, and how fast I can actually get it.
NOTE: The ND 3.8 is for Photography only, NOT for visual use, so if anyone gets some only use the LiveView or similar functionality. Get the ND 5 if you want to use it visually.
--- End quote ---
One option is to stack ND filters to reach the desired optical density. Being that the ND scale is logarithmic, it is possible to stack an ND3 and ND0.9 together to get an effective optical density of ND3.9 (~8000x light reduction). That optical density works well for solar photography when using very fast shutter speeds and strongly stopped down apertures. I definitely agree that Live View should be used to confirm framing and focus instead of the viewfinder. I will be using this technique for the May 20th eclipse as well as the upcoming solar transit of Venus on June 5th. B&H has many B+W ND3 and ND0.9 filters in stock so that is an option for folks who can't find dedicated filters. Just make sure you don't buy an ND .3 instead of an ND3. :D The added benefit of getting two separate filters is that later you can use the ND3 and ND0.9 individually for varying levels of smoothing out water and cloud movement in your photos. See more on this effect here: http://www.redbubble.com/people/peterh111/journal/4421304-the-ultimate-guide-to-neutral-density-filters
--- End quote ---
I'm not sure that the normal ND filters will work, as they don't block enough of the IR & UV that the direct sun produces. Especially if the sun is a large portion of the with a super-telephoto.
jabbott:
--- Quote from: Drizzt321 on May 09, 2012, 12:21:21 AM ---I'm not sure that the normal ND filters will work, as they don't block enough of the IR & UV that the direct sun produces. Especially if the sun is a large portion of the with a super-telephoto.
--- End quote ---
CMOS sensors for DSLRs already have highly efficient IR filters built-in, and you can always add a UV filter to the ND stack if you are concerned about UV effects. The detail you would get is nowhere near as good as having a dedicated Hydrogen-alpha filter though. I purchased my ND filters for waterfalls and only afterward realized they could be used for solar photography when stacked... so there are definitely better options out there. According to transitofvenus.org, you can use #14 or greater welding glass as an option. I'm not sure if or how that would alter color however. The most interesting photos of the sun I've seen online use an H-alpha filter which brings out a lot of detail.
Here is a photo of the sun I took with stacked ND3 and ND0.9 filters with a 70-200 II, 2x Extender II and a Rebel T2i. I used 1/800s shutter with f/22 aperture at ISO 100 and 400mm focal length. I shot this indoors through unclean windows so that likely distorted the image somewhat. Using a diffraction-limited aperture also reduced sharpness. The dark spots shown are sunspots that I verified using the SDO/HMI Continuum image from the same day. I probably could have focused better but I kept focus time to a minimum to avoid frying things. ;)
Back to the original poster's question, I would say other uses would include 1) really long exposures of waterfalls / the ocean in brightly lit scenes, 2) photos of welding or 3) molten metal in crucibles.
Drizzt321:
Hmm...that's interesting jabbott. I'll look into that if I can't get the right kind of solar filter. I'm going to bracket every single shot anyway, that way I can try and do some stacking & maybe some HDR on the wide angle shots, or even just cut out the sun to get the correct exposure on the landscape & the sun.
PeterJ:
--- Quote from: squarebox on May 08, 2012, 08:04:55 PM ---Is there any use for a ND100000 filter outside of taking a solar eclipse?
The only thing I could think of is doing a super long exposure in the city to remove people.
--- End quote ---
I bought a Thousand Oaks Optical solar filter on a recommendation from here, it was the kind made from a blank polymer and it worked well for a partial solar eclipse. However with the idea of using it for other purposes I took it out in the back yard and manually focused a 70-200 on a rose bush, worked out the rough exposure change, fitted the filter and took a few shots around my estimated exposure time.
I seemed to get the exposure right but the colour reproduction was beyond bad, so bad you couldn't tell the difference between primary colours and the loss of contrast between features meany it was actually hard to tell what it was a photo of. No doubt it would depend on what the filter is made from but if you're considering a new one you'd want to check into it and not assume it will be OK for general photography. I didn't keep that photo but did like the results from that filter with the sun:
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