17 replies to this topic

[CreatorsHand]

I have access to four different name brand solar filters and I figured that there might be some interest in a head to head comparison, so when I had a few minutes of clear skies today and a few minutes of spare time I got out my Canon 7D Mark II and 500mm f/4L lens, and took a series of images with each filter. All images were captured at f/4 and ISO 100, with the lens mounted on a gimbal head on my tripod. I shot a series of 7 bracketed images 1/3 stop apart, with the only change being the shutter speed. I had intended to shoot at f/8 so I could compare to the images I captured during the eclipse in 2017 (I used one of the filters for that eclipse), but in the haste to catch a rare section of clear sky I forgot to set the aperture to f/8. I plan to reshoot them on the next clear day (which will hopefully be early next week from the forecast). I then took the ones that were visually close into Lightroom and compared histograms, and chose one from each filter where the histograms peaked and stopped at about the same point (which happened to be about 7/8 to the right edge of the histogram for each). The three "orange" white light filters each had red peaks that matched fairly well on the right end, with closely matched peaks of green (slightly) and blue (significantly) lower on the histogram, while the "white" Baader filter had color peaks that were more closely matched (the blue peak was slightly higher). The White Balance on all images was the same, which was the camera "SUNNY" setting, and came into Lightroom at 5100K. I thought that doing it by histogram instead of visually might remove some subjectivity. In the process of shooting these, I discovered how large that sunspot is.

 

The four filters I used were:

 

-1) Thousand Oaks Optical glass filter. While they aren't sold new anymore, I was fortunate to be able to purchase a used one in excellent condition. I chose this one as the reference, as they have been around a long time and people have experience with them.

 

-2) Spectrum Telescope glass filter.

 

-3) Thousand Oaks Optical SolarLite film filter. I used this for the eclipse in 2017. As you can see in the image, this has a significant color bleed into the area around the Sun, but I found that it is fairly simple to remove the vast majority of it using the Dehaze slider in Lightroom.

 

-4) Baader Astro Solar film. This was surprisingly the same exposure as the Thousand Oaks glass filter, based on the histogram peaks on the right of the histogram, although the limbs of the Sun are not quite as dark, which is also reflected in the histogram.

 

Thousand Oaks Optical glass - 1/800 sec

 

Spectrum Telescope glass - 1/320 sec

 

Thousand Oaks Optical SolarLite film - 1/60 sec

 

Baader Astro Solar film - 1/800 sec

 

 

 

Thousand Oaks Optical SolarLite film, with the Dehaze slider all the way to the right, and a slight decrease in the Shadows slider, just to show that it can be improved fairly easily.

 

These could all be edited in Lightroom or other editing software to bring up the contrast or vibrancy, or bring out the sunspots, but my goal was to showcase how my testing found they compared to help plan for this upcoming eclipse. Whether there are variations within specific filter brands I can't say, but these are the results I got today.

 

Paul

[banjo1000]

To my eye, the seeing on the final exposure with AstroSolar was poorest yet the details of the sunspots are best. In part that may be because of the balanced use of al 4 RGGB pixels. The Thousand Oaks shifts towards the red means that a single R pixel dominates so that the effective number of pixels is smaller.

You didn’t state explicitly, but it appears your test was with AS OD 5.0 visual film. Photographically, you would find superior results with AS OD3.8 photo film. I read and confirmed to my own satisfaction that OD 3.8 paired with an Oxygen III filter gave still better resolution “white” light pictures when stacked.

Edited by banjo1000, 09 February 2024 - 02:54 AM.

[CreatorsHand]

To my eye, the seeing on the final exposure with AstroSolar was poorest yet the details of the sunspots are best. In part that may be because of the balanced use of al 4 RGGB pixels. The Thousand Oaks shifts towards the red means that a single R pixel dominates so that the effective number of pixels is smaller.

You didn’t state explicitly, but it appears your test was with AS OD 5.0 visual film. Photographically, you would find superior results with AS OD3.8 photo film. I read and confirmed to my own satisfaction that OD 3.8 paired with an Oxygen III filter gave still better resolution “white” light pictures when stacked.

The images captured with the Baader filter were a couple hours after the other three, as I didn't have it available in time to use before the sky clouded over earlier, so it is very possible that the seeing was worse. A rain storm (not something I usually think about in early February in the U.P. of Michigan) started about 20  minutes afterwards also.

 

I had no idea what "AS OD 5.0" or "AS OD 3.8" even refers to, so I wouldn't have been able to state anything about it explicitly, but bought it from Astro-Physics at their recommendation for use with their telescopes (it will ultimately be used with an A-P Traveler, so I figured they would know best). Looking it up on their website, it apparently is an AstroSolar OD 5.0. I purchased the ASTF version of the Baader filter. After going to Kendrick Astro's website (they make filters that Astro-Physics has also sold), I think I may understand what you are referring to. They used to sell solar filters made for photography (using Baader AstroSolar film), but not many because it could only be used for photography, not visual (I'm guessing the 3.8 and 5.0 refer to the ND rating (?)), so they stopped selling the photographic filters in 2016 and only sell the visual filters, as they can also be used for photography. I'm wondering if liability might have also been an issue.

 

You never know what you will learn,

Paul

[RNSpeed]

I have the Spectrum Telescope Glass solar filter and I like it better than the Baader film, This is is an image straight from my Micro 4/3 OM-5 Camera from yesterday.  It was connected to my AP Stowaway

 

Camera:  OM System OM-5 Micro 4/3

Telescope: AP Stowaway

Exposure: 1/1000 ISO 200

No after processing just resized to follow forum rules, 2nd image is the copped Sun

 

Regards

 

Ray

 

 

Attached Thumbnails

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[CreatorsHand]

I have the Spectrum Telescope Glass solar filter and I like it better than the Baader film, This is is an image straight from my Micro 4/3 OM-5 Camera from yesterday.  It was connected to my AP Stowaway

 

Camera:  OM System OM-5 Micro 4/3

Telescope: AP Stowaway

Exposure: 1/1000 ISO 200

No after processing just resized to follow forum rules, 2nd image is the copped Sun

 

Regards

 

Ray

 

 

In some ways, I do too. It does a better job picking up the natural limb darkening, and I like the orange color even if the white image from the Baader filter might be more natural. I added the Baader film filter to the test because A-P, and Roland in particular, recommends it and sells them. I have a Photo version of the Baader filter coming, which has an O D of 3.8 instead of 5.0 and isn't safe for visual use since it lets 4 stops more light in but has been tested to a Strehl of 94 to 96, and plan to test that as well. I don't have a direct comparison yet, as the image with the Baader film was captured several hours after the others, and as banjo1000 pointed out above, the Seeing had apparently deteriorated due to the storm coming in, but hope to do that as soon as we get clear skies again. It is hard to compare the exposure of your image to mine without knowing what the focal ratio was, which depends on which version of the Stowaway you have and whether you used a TCC or FF. The Spectrum Telescope glass filter is definitely a viable option. Based on my comparison, it lets about  1 1/3 stops less light through.

 

Paul

[maj]

Thanks for posting those comparisons. This is a jpg image I took yesterday with a Nikon D850 w/ 500mm PF lens with Baader AstroSolar film.  ISO 200, 1/5000s, f/8.  This was shot with basic settings - I hope that the IQ could improve by adjusting camera settings to reduce the effects of mirror slap and shutter vibration.  The second image was cropped and adjusted on my iPad. I’m thinking this is probably OK for the eclipse but could I get better results with any other film or glass filter that would be available?

 

 

adjusted image:

Edited by maj, 11 February 2024 - 02:57 PM.

[CreatorsHand]

Thanks for posting those comparisons. This is a jpg image I took yesterday with a Nikon D850 w/ 500mm PF lens with Baader AstroSolar film.  ISO 200, 1/5000s, f/8.  This was shot with basic settings - I hope that the IQ could improve by adjusting camera settings to reduce the effects of mirror slap and shutter vibration.  The second image was cropped and adjusted on my iPad. I’m thinking this is probably OK for the eclipse but could I get better results with any other film or glass filter that would be available?

 

IMG_2644.jpeg

 

adjusted image:
DSC_1149.jpeg

You are welcome maj. Assuming that your settings are correct as posted, and your shutter speed was 1/5000 sec, you must have the O D (Optical Density) 3.8 Photo version of this film, as (based on my calculations) those settings are 3 2/3 stop less exposure than my Baader Astro Solar image (which was captured with a filter with the O D 5.0 material), and O D 3.8 theoretically has 4 stops less Optical Density than the more common O D 5.0 AstroSolar Safety (Visual) film. If, on the other hand, that is a typo and the shutter speed is actually 1/500 sec, then that is equivalent to 1/3 stop less exposure than my image, which would make sense as well. Note that if you do have the O D 3.8 AstroSolar, that is not safe for visual use, so make sure that nobody looks through a telescope with an eyepiece using that filter. To the best of my knowledge, there is no other filter that is better for clarity than one using Baader AstroSolar filter material, which has been tested to have a 94 to 96 percent Strehl rating, according to Baader. The main difference between the two versions seems to be the O D rating, and whether it is safe for visual use. I did find reference to the Baader Solar Continuum filter, which is supposed to enhance details details on the Sun's surface. Your images does have more surface details than I have seen with any other filter I have used. As for mirror slap/shutter vibration, it has always been my understanding that would really only be a problem with shutter speeds in the neighborhood of 1/8 sec, and that significantly longer or shorter shutter speeds would not be effected. The bigger problem would be atmospheric turbulence (less than Excellent Seeing), which would likely have much more effect on the image clarity than mirror slap. That all being said, I am certainly not a solar filter material expert, and what I have stated is based on my current understanding.

 

Paul

[maj]

Thanks for the input Paul.  The settings that I posted (ISO 200, 1/5000 sec, and f/8) were correct.  I used an Astromania Deluxe Solar Filter that appears to be sold as a telescope filter.

 

https://astromaniaop...riantsId=10156 

 

They did not post specs, I got it for the 2017 eclipse with good results. For the full disk in 2017, my settings were ISO 640, 1/6400 sec, f/8.  The web site claims that the filter complies with ISO 12312-2: 2015.  If this filter is OD 3.8, l’m now wondering if it’s safe to view through the camera viewfinder?

[CreatorsHand]

Thanks for the input Paul.  The settings that I posted (ISO 200, 1/5000 sec, and f/8) were correct.  I used an Astromania Deluxe Solar Filter that appears to be sold as a telescope filter.

 

https://astromaniaop...riantsId=10156 

 

They did not post specs, I got it for the 2017 eclipse with good results. For the full disk in 2017, my settings were ISO 640, 1/6400 sec, f/8.  The web site claims that the filter complies with ISO 12312-2: 2015.  If this filter is OD 3.8, l’m now wondering if it’s safe to view through the camera viewfinder?

You are welcome maj. I would say that with your Astromania filter it would be, as the settings you used in 2017 would be equivalent to 1/1000 second at f/8 and ISO 100, if my calculations are correct, which is 1/3 stop less exposure that I got with both my Thousand Oaks Optical glass and Baader AstroSolar film filters. I would say that, based on your settings for the Baader AstroSolar you posted previously, that it is NOT safe to look through the viewfinder when you are using that filter, and I would tape the viewfinder off to make sure you don't use it in the excitement of eclipse day, or while you are practicing. I would also recommend using the lowest ISO you can, to pick up the maximum dynamic range your camera can capture, since shutter speed should not be an issue.

 

Paul

 

Paul

[JethroXP]

I purchased the Thousand Oaks Optical Silver-Black polymer sheets to make my own filters.  But as I read a bit more I came to the conclusion that their SolarLite film was probably better for photography (thus the higher price) so I ordered that too and that's what I made my initial homemade filters with.  I finally had a sunny day to test and I struggled to find focus, even beginning to suspect there was something wrong with my camera or lens.  The 500mm lens I'm using has an aperture range of 6.3 to 32 and while I intended to use it wide open at 6.3 I could only get passable focus at f/32.  Then I decided to try the Silver-Black polymer.  I hadn't fashioned it into a filter yet so I just cut an appropriately sized piece and taped it to the end of the lens. I was amazed at the difference, I was able to obtain a sharp focus on the visible sunspots even at f/6.3.  I've also since ordered some of the Baader AstroSolar film and will made filters from it and the Thousand Oaks optical Silver-black polymer to compare.

[CreatorsHand]

I purchased the Thousand Oaks Optical Silver-Black polymer sheets to make my own filters.  But as I read a bit more I came to the conclusion that their SolarLite film was probably better for photography (thus the higher price) so I ordered that too and that's what I made my initial homemade filters with.  I finally had a sunny day to test and I struggled to find focus, even beginning to suspect there was something wrong with my camera or lens.  The 500mm lens I'm using has an aperture range of 6.3 to 32 and while I intended to use it wide open at 6.3 I could only get passable focus at f/32.  Then I decided to try the Silver-Black polymer.  I hadn't fashioned it into a filter yet so I just cut an appropriately sized piece and taped it to the end of the lens. I was amazed at the difference, I was able to obtain a sharp focus on the visible sunspots even at f/6.3.  I've also since ordered some of the Baader AstroSolar film and will made filters from it and the Thousand Oaks optical Silver-black polymer to compare.

I'm not familiar with the T O Silver-Black Polymer film (in 2106 I purchased their Black Polymer film prior to the Mercury Transit for my first filter, which they apparently don't sell anymore; maybe the Silver-Black polymer film is a variation of that). I find it interesting that you were able to focus at f/32 but not wide-open; I would think that would make the view extremely dark. The Baader film and filters made from it are recommended by, and sold by, Astro-Physics as the best option optically. At this point I am planning on using a  Baader O D 5.0 filter on my Traveler, and a Baader O D 3.8 filter on my 500mm f/4. It would be interesting to know what you find with the comparison. The Baader will likely allow faster shutter speeds, but will give you a whitish image instead of the orange of the TO film.

 

Paul

[JethroXP]

I'm not familiar with the T O Silver-Black Polymer film (in 2106 I purchased their Black Polymer film prior to the Mercury Transit for my first filter, which they apparently don't sell anymore; maybe the Silver-Black polymer film is a variation of that). I find it interesting that you were able to focus at f/32 but not wide-open; I would think that would make the view extremely dark. The Baader film and filters made from it are recommended by, and sold by, Astro-Physics as the best option optically. At this point I am planning on using a  Baader O D 5.0 filter on my Traveler, and a Baader O D 3.8 filter on my 500mm f/4. It would be interesting to know what you find with the comparison. The Baader will likely allow faster shutter speeds, but will give you a whitish image instead of the orange of the TO film.

 

Paul

Hey Paul,

This is the Silver-Black Polymer
https://thousandoaks...polymer-sheets/

And this is their SolarLite Polymer
https://thousandoaks...-filter-sheets/

And this is how they describe the difference between them:

What is the difference between Silver-Black Polymer film and SolarLite film?

Silver-Black is good for up to 100x magnification, SolarLite up to and over 100x.

 

And yes, at f/32 I had to increase the exposure to 3/10ths of a second vs. 1/100th of a second at f/6.3 and that was concerning as well because it was going to throw of the timing I'd planned for the images.  Unfortunately we have another round of rain and snow in the forecast so while the Baader film is supposed to be here in a couple days, it will more a week or more before I can test again.

[CreatorsHand]

Hey Paul,

This is the Silver-Black Polymer
https://thousandoaks...polymer-sheets/

And this is their SolarLite Polymer
https://thousandoaks...-filter-sheets/

And this is how they describe the difference between them:

What is the difference between Silver-Black Polymer film and SolarLite film?

Silver-Black is good for up to 100x magnification, SolarLite up to and over 100x.

 

And yes, at f/32 I had to increase the exposure to 3/10ths of a second vs. 1/100th of a second at f/6.3 and that was concerning as well because it was going to throw of the timing I'd planned for the images.  Unfortunately we have another round of rain and snow in the forecast so while the Baader film is supposed to be here in a couple days, it will more a week or more before I can test again.

Thank you for the links, Jason. What is interesting is that if you zoom in on the instruction sheet for either of them, it talks about glass filters (which they don't sell anymore), SolarLite film and Black Polymer film, so I may have surmised correctly that the Silver-Black Polymer is a variation of the original Black Polymer film.

 

We have had nearly constant clouds for months here, and it has been hard to get out to test filters, but I did have a sunny day a couple days ago. Based on my most recent tests, I intend to use the following for planning purposes, and for my filters, believe these are comparable exposures. Based on images captured with a 7DII and 500mm f/4L at f/8, ISO 100

 

-SolarLite: 1/15 sec

-Baader AstroSolar O D 5.0: 1/500 sec

-Baader AstroSolar O D 3.8: 1/8000 sec (If I use this filter, I will probably use 1/4000 sec at f/11)

 

As you can see, the Baader AstroSolar O D 5.0 (which is what I assume you have coming) lets substantially more light through than the SolarLite. The Baader AstroSolar O D 3.8 lets an additional 4 stops of light through, and is NOT safe for visual use, which means you can't use the camera viewfinder either, and should block that off if you were going to use it. This will give you a starting point, but you should test things for yourself and compare. It is difficult to compare images between SolarLite and AstroSolar film as the color palette is different between the two filters, and what you decide is a comparable exposure may vary depending on what criteria you use to compare them, and how you test them, so you should compare images captured with your equipment and decide for yourself what settings to use. The good thing about it is as long as they are not overexposed, the exposure of images can be reduced in post-processing, and as you probably know it is easier and gives better results to reduce than increase exposure so you don't have to get it perfect..

 

Clear skies,

Paul

[WillyKidAZ]

Hi Paul. Thanks for sharing! Quick question, what was the SKU and/or manufacturer model number for the Spectrum Telescope glass filter you used that fit your 500mm lens?

[CreatorsHand]

Hi Paul. Thanks for sharing! Quick question, what was the SKU and/or manufacturer model number for the Spectrum Telescope glass filter you used that fit your 500mm lens?

Hi Willy, you are welcome. The Canon 500mm f/4L is somewhat in between the sizes they offered at the place I purchased it, at least if you want to put it on the lens hood. I got their model ST712G, which is a little oversize, and added some felt tape to make it fit. It looks like their Model #ST600G would fit just about perfect if you wanted one that would fit the front of the lens without the lens hood. Since I had to take it off during the eclipse and put it back on, I chose the larger one so I could use the lens hood. Looking at Spectrum Telescope's website, they also have a Model #ST675G, which wasn't offered where I purchased my filter, which should fit just the lens hood just about right; the lens hood for mine (I have version I, and I think the hood for the IS II may be larger) measures 162mm, and the ST165G is supposed to fit 158mm to 169mm. I hope that helps.

 

Paul

[JethroXP]

Thank you for the links, Jason. What is interesting is that if you zoom in on the instruction sheet for either of them, it talks about glass filters (which they don't sell anymore), SolarLite film and Black Polymer film, so I may have surmised correctly that the Silver-Black Polymer is a variation of the original Black Polymer film.

 

We have had nearly constant clouds for months here, and it has been hard to get out to test filters, but I did have a sunny day a couple days ago. Based on my most recent tests, I intend to use the following for planning purposes, and for my filters, believe these are comparable exposures. Based on images captured with a 7DII and 500mm f/4L at f/8, ISO 100

 

-SolarLite: 1/15 sec

-Baader AstroSolar O D 5.0: 1/500 sec

-Baader AstroSolar O D 3.8: 1/8000 sec (If I use this filter, I will probably use 1/4000 sec at f/11)

 

As you can see, the Baader AstroSolar O D 5.0 (which is what I assume you have coming) lets substantially more light through than the SolarLite. The Baader AstroSolar O D 3.8 lets an additional 4 stops of light through, and is NOT safe for visual use, which means you can't use the camera viewfinder either, and should block that off if you were going to use it. This will give you a starting point, but you should test things for yourself and compare. It is difficult to compare images between SolarLite and AstroSolar film as the color palette is different between the two filters, and what you decide is a comparable exposure may vary depending on what criteria you use to compare them, and how you test them, so you should compare images captured with your equipment and decide for yourself what settings to use. The good thing about it is as long as they are not overexposed, the exposure of images can be reduced in post-processing, and as you probably know it is easier and gives better results to reduce than increase exposure so you don't have to get it perfect..

 

Clear skies,

Paul

Paul,  This great insight, thank you!  This also explains why in my initial testing with the SolarLite filter my images seemed much darker than I expected.  I was using the exposures recommended by Elcipse Orchestrator for my ISO and f-ratio but I suspect EO is probably assuming the use of Baader film or similar filter since the exposures all seem too fast for the SolarLite.  Or maybe EO is tuned to true ND 5.0 which the Baader film is but perhaps the SolarLite has a higher ND value?

[JethroXP]

So I think I answered my own question, I just noticed that on Xavier Jubier’s eclicpe exposure calculation page he lists SolarLite as ND 5.6 and the exposures using SolarLite need to be 4x longer than those with an ND 5.0 filter.  Now it’s all making sense!

 

http://xjubier.free....seExposure.html

Edited by JethroXP, 25 February 2024 - 12:58 PM.

[JethroXP]

Having tested Thousand Oaks SolarLite and their Black Polymer, as well as Baader AstroSolar (ND 5.0) film I can say unequivocally that the Baader film is better for photographic use.  I struggled to find good focus with my Nikon Z6 (500mm) and Nikon P1000 (up to 2000mm) using the SolarLite.  The Black Polymer was definitely better, but the Baader AstroSolar easily outperforms them both.  I haven't yet done a visual comparison, but for photographs Baader is the clear winner.  I also found it very easy to colorize the images from the Baader film to give them a pleasing orange color if you might be concerned about that compared to the already-orange films from Thousand Oaks optical.

Edited by JethroXP, 06 March 2024 - 04:03 PM.