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Rumors => Lenses => Topic started by: PeterJ on September 04, 2011, 05:10:04 AM

Title: Filter for direct sun photography
Post by: PeterJ on September 04, 2011, 05:10:04 AM
In a few months they'll be a partial eclipse visible here in Tasmania and I'd like to take a few snaps of it. I don't want to fork out too much for the excercise so will be using my existing 7D + 70-200 + 2x TC but don't mind buying a filter which I'm sure I'll find other uses for. While I don't want to fry my 7D sensor I'm even less inclined to fry my eyes so after some Googling so far my thoughts are:

Purchase a Hoya NDx400 77mm filter which is a 9 stop / 1/500 filter and shoot at around f/11. I've got no intention of looking through the viewfinder so thought I'd quickly compose and focus in live view so the sensor isn't exposed a long time and then switch back to normal mode, lock the focus and take the shots using an intervalometer for a time lapse sequence. I haven't worked it out properly yet but guess at 640mm effective length the sun will be small enough and won't move enough in the 5 minute period to need me to recompose the shot.

Anyway I just thought I'd post and see if anyone sees any holes in my plan or better filters and/or techniques I can use? One possible thing I could do is 10 mins before starting is focus the lens on something at infinity and lock it, but seem to remember reading that somewhere that apparently large objects in the sky may not require infinity focus, but can't really remember the theory and if it was a reputable source.
Title: Re: Filter for direct sun photography
Post by: Haydn1971 on September 04, 2011, 05:23:25 AM
I suspect the sun will move quite a fair amount in 5 minutes !  I have a B&W ND1000 which at f22, a 25-30 second exposure is about correctly exposed on overcast and blue sky days and I've had numerous empty roads pictures, a novelty I still can't stop smiling at, but my point being that I suspect with the sun bleaching past the moon, a shorter exposure may work.
Title: Re: Filter for direct sun photography
Post by: PeterJ on September 04, 2011, 05:46:10 AM
Hi Haydn, thanks for the info. Do you know if the B&W ND1000 is still a current product? While having a look around it looked like it may be a better alternative but I got the impression they no longer made them.

I forgot when I posted I had a little app on my droid phone that calculates FOV and it comes up with 2 degrees vertically for that combination. My astronomy / trig is not so good but think at 360 degrees per day which is 1440 minutes it should move 360 / 1440 * 5 = 1.25 degrees which should be OK if I anticipate the direction and get the first shot near the edge, or could go portrait for 3 degrees and crop later. Then again that's not taking into account the size of the sun, so might be something to try in advance once I have a filter.
Title: Re: Filter for direct sun photography
Post by: lol on September 04, 2011, 05:46:44 AM
If you want to photograph the sun directly, try this stuff: http://www.baader-planetarium.com/sofifolie/sofi_start_e.htm

Example output with that filter:
(https://lh5.googleusercontent.com/-VnY9jFGHb9M/TeoiHnKUPSI/AAAAAAAAGhk/mF-rpGWKiN8/s400/sun201106040-s.jpg) (https://lh5.googleusercontent.com/-VnY9jFGHb9M/TeoiHnKUPSI/AAAAAAAAGhk/mF-rpGWKiN8/s800/sun201106040-s.jpg)
100-400L x2 for 800mm. f/11 1/1000s ISO800 cropped and resized.
Title: Re: Filter for direct sun photography
Post by: Haydn1971 on September 04, 2011, 06:03:05 AM
Hi Haydn, thanks for the info. Do you know if the B&W ND1000 is still a current product? While having a look around it looked like it may be a better alternative but I got the impression they no longer made them.

Bought mine about 3 months ago, about £85 for a 72mm one - it does give a slight yellow brown tint to images on my 450D, but playing with colour levels is easy.
Title: Re: Filter for direct sun photography
Post by: aldvan on September 04, 2011, 06:15:38 AM
Solar photography is quite a serious affair, something to take with great care and prudence.
The solar filter I have in my Mead LX-200 telescope seems a dark mirror and the manufacturer suggesta to check it very carefully for any small hole in the treatment, since the consequences for eyes and sensors can be dramatic. Follow a very well learned procedure before starting to aim and checking, since a small mistake can be irreparable.
By the way, the result is really exciting... I'm attaching an example from  my Meade...
Don't forget that a very dark filter requires slow exposition times, something in the 1/10-1/50 range and the sun moves very fast. For that reason a telescope follows the object by computer controlled microengines.
Title: Re: Filter for direct sun photography
Post by: PeterJ on September 04, 2011, 08:13:06 AM
If you want to photograph the sun directly, try this stuff: http://www.baader-planetarium.com/sofifolie/sofi_start_e.htm
Nice photo and that sounds like a good product, from what I could see it's just a film layer so how did you go about mounting to the front of your lens? I saw their suggestion of rolled cardboard for a telescope but can't see that working too well with the small ridge on an DSLR lens, maybe same idea near the base of the lens hood might be OK? The price versus the large size of the film certainly makes it look like an attractive option to experiment with.

Solar photography is quite a serious affair, something to take with great care and prudence.
The solar filter I have in my Mead LX-200 telescope seems a dark mirror and the manufacturer suggesta to check it very carefully for any small hole in the treatment, since the consequences for eyes and sensors can be dramatic. Follow a very well learned procedure before starting to aim and checking, since a small mistake can be irreparable.
Another impressive piece of work, thanks for the advice on pinholes I see the site lol linked to mentions the importance of that also. Don't worry I'm taking it seriously, reason for my post because I knew I'd get some great tips on things I hadn't thought of :).
Title: Re: Filter for direct sun photography
Post by: lol on September 04, 2011, 08:50:41 AM
The film has instructions on mounting it to a cardboard sandwich. I then fixed that cardboard holder onto a spare filter so I can add/remove it from the lens easily.
Title: Re: Filter for direct sun photography
Post by: TexPhoto on September 04, 2011, 11:59:24 AM
I shoot the sun all the time, even video thrugh a 400mm f2.8 and have not effected my sensor.  You could add 1 or more polarizing filters to knock down some stops. or a 3-4 stop ND filter might be more usefill for other shooting.

Of course you can use live view to avoid exposing your eyes.

A quick search of ebay for "welding glass" finds $3 sections of glass that should do what you want.
Title: Re: Filter for direct sun photography
Post by: epsiloneri on September 04, 2011, 03:06:31 PM
I shoot the sun all the time, even video thrugh a 400mm f2.8 and have not effected my sensor.

I can't believe I'm reading this advice from you! It's very dangerous to do what you suggest. Please note that you should always place any filter in front of the front lens. The 400/2.8 has a rear mounted filter which is not suitable for solar filters. The reason is that the light will get concentrated on the rear filter, which is bad if you point it towards the Sun - the filter will heat up and possibly crack/be destroyed with disastrous consequences for the sensor (or worse, your eye). Ever used a magnifying glass to light a fire? Then you know what I'm talking about.

For continuum light solar filters I've tried and recommend those from Thousand Oaks Optical (http://www.thousandoaksoptical.com/solar.html), they even have camera threaded filters. For a 400/2.8 I would recommend purchasing a mylar sheet (or black polymer) and produce a filter yourself for placement in front of the lens.

For more tips about observing total and partial solar eclipses I recommend NASA's eclipse bulletin which are published in connection with major eclipses. There is none for the Nov 25 one, but you can have a look at older bulletins as the practical information is the same: http://eclipse.gsfc.nasa.gov/SEpubs/2010/rp.html (http://eclipse.gsfc.nasa.gov/SEpubs/2010/rp.html).

Since you're in the neighbourhood, you may also want to check out the total solar eclipse on Nov 13 next year in NE Australia and New Zealand. If you haven't seen a total eclipse I would highly recommend it - a partial eclipse does not even come close in comparison.
Title: Re: Filter for direct sun photography
Post by: epsiloneri on September 04, 2011, 04:04:04 PM
My astronomy / trig is not so good but think at 360 degrees per day which is 1440 minutes it should move 360 / 1440 * 5 = 1.25 degrees which should be OK if I anticipate the direction and get the first shot near the edge, or could go portrait for 3 degrees and crop later. Then again that's not taking into account the size of the sun, so might be something to try in advance once I have a filter.

I checked your numbers BTW, they are OK. The Sun is only 0.5 deg in diameter. But where do the 5 min come from? The eclipse should start at least 30 min before sunset. I haven't figured out the exact circumstances, but I imagine there being an opportunity here for a nice partially eclipsed sunset image. Without a filter when the sun is close enough to the horizon, just like you normally would shoot a sunset. Trying in advance is a good idea, in particular if you want to find the best spot for the sunset.

One idea is to find the exact spot where the sun will set (e.g. by checking the day before - remember, this location moves with time so don't attempt to find it too many days in advance) then go back and compose the image well before sunset on the eclipse day and make a time series that shows the sun entering the frame and then setting partially eclipsed. For best result, use manual mode and an exposure that you determined on the previous "trial" sunset. Focus on something distant using live view and manual focus. Start your time-series 10-15 min before sunset. Don't forget to post your results here :)

I have the NDx400 filter, and it's not really dark enough for day time photography of the sun - you can do it, but only with the shortest exposure time and smallest aperture (resulting in resolution loss due to refraction). As a comparison, the Thousand's Oak solar filter I previously referred to attenuates light by a factor of 100,000, or 16.6 stops - enough to safely look through. Because your particular partial eclipse is at sunset, it shouldn't be a problem for you though.
Title: Re: Filter for direct sun photography
Post by: PeterJ on September 04, 2011, 10:44:56 PM
For continuum light solar filters I've tried and recommend those from Thousand Oaks Optical (http://www.thousandoaksoptical.com/solar.html), they even have camera threaded filters. For a 400/2.8 I would recommend purchasing a mylar sheet (or black polymer) and produce a filter yourself for placement in front of the lens.
Thanks for that and all the other tips, I've just e-mailed to get a shipping quote on a 77mm threaded filter, they sound convenient and I don't imagine I'll be buying any big primes in the near future.

I checked your numbers BTW, they are OK. The Sun is only 0.5 deg in diameter. But where do the 5 min come from? The eclipse should start at least 30 min before sunset.
I got that number from http://en.wikipedia.org/wiki/List_of_solar_eclipses_in_the_21st_century although I see now it's the central duration so I'll follow you advice of checking the position the day before for framing so it enters the frame during the sequence. Thanks once again for all the advice, I'm just about to take a better look at the NASA info and I'll be sure to post the results  :).
Title: Re: Filter for direct sun photography
Post by: epsiloneri on September 05, 2011, 02:46:47 AM
But where do the 5 min come from? The eclipse should start at least 30 min before sunset.
I got that number from http://en.wikipedia.org/wiki/List_of_solar_eclipses_in_the_21st_century although I see now it's the central duration so I'll follow you advice of checking the position the day before for framing so it enters the frame during the sequence.

Since the eclipse is partial, there is no central duration. Perhaps you looked at the wrong entry? Partial eclipses are regularly more than an hour in length, but because your starts just before sunset, you'll only have half an hour or so before the sun sets (partially eclipsed). Good luck anyway, and I look forward to see your results!
Title: Re: Filter for direct sun photography
Post by: PeterJ on September 05, 2011, 03:36:38 AM
Ahh yes I must have looked at the wrong column. Just had a check and the time of greatest eclipse is about 3 hours before sunset for that time of year. That's probably good though because from my location I don't get very good sunsets because of a mountain range that probably covers at least the last half hour of sunset.
Title: Re: Filter for direct sun photography
Post by: epsiloneri on September 05, 2011, 05:32:04 AM
Sorry, somehow I thought Tasmania was close to New Zealand, but I now realise it's much closer to main land Australia. That means the sun will not set partially eclipsed, in fact the moon will only nudge the Sun as seen from Tasmania and the eclipse will only last some 30-40 min, starting at ~07:30-07.40 UT, corresponding to 18:30-18:40 local DST, depending on where your are.
Title: Re: Filter for direct sun photography
Post by: PeterJ on September 05, 2011, 08:04:29 AM
Since having a further look today at few a links you'd provided and noticing a link on Wikipedia that shows the area that will be covered I realised it won't be too dramatic from here with probably only 10% covered. Anyway I'll proceed as planned, no harm seeing how it goes and from time to time I've seen some shots that would be interesting straight into the sun that I wouldn't want to take without a proper filter so I'm sure I'll find some other uses for it.
Title: Re: Filter for direct sun photography
Post by: PeterJ on November 25, 2011, 03:52:27 AM
Since posting I found a good Javascript eclipse calculator, coverage was only 1.6% so as you'd expect nothing too dramatic. But anyway thought as promised I'd better come back and post initial results with the 7D + 2x III + 70-200 f/2.8. I have a few more to sift through and might be able to sharpen but after a quick look this was probably the best at f/9 and 1/200 using the Thousand Oaks filter:

(http://i44.tinypic.com/znv6v5.jpg)

Anyway good practice run for the fuller eclipse next year, might even see if I can get more up north of the country where it'll be a full eclipse ;D.
Title: Re: Filter for direct sun photography
Post by: handsomerob on November 25, 2011, 05:38:16 AM
nice shot! thx for sharing.
Title: Re: Filter for direct sun photography
Post by: epsiloneri on November 25, 2011, 06:55:33 AM
Nice! The softness of the sunspots and lunar rim is likely due to the low angle of the Sun over the horizon (giving a large airmass with turbulence). Was it handheld or on a tripod? I find the best focus for partial eclipses is achieved using "live view" on the lunar rim.
Title: Re: Filter for direct sun photography
Post by: PeterJ on November 25, 2011, 07:42:51 AM
Nice! The softness of the sunspots and lunar rim is likely due to the low angle of the Sun over the horizon (giving a large airmass with turbulence). Was it handheld or on a tripod? I find the best focus for partial eclipses is achieved using "live view" on the lunar rim.
Thanks for your earlier advice epsiloneri, I hadn't thought about air turbulence but at that time it was getting close to a mountain range that does have a lot wind and cloud cover. I was using a fairly decent tripod and shutter release, only thing I realised later is that I should have used mirror lock-up as well, just had it in stuck in my mind not to use it because of the sun but of course wouldn't have mattered with the filter ::).

I had a play around with various focus options yesterday taking a few test shots with manual / AF and viewfinder / liveview. Apart from liveview / contrast detect AF which was a dodgy as usual I didn't find much difference between all of them, so ended up just taking an initial phase-detect focus on the center AF point making sure it was on the edge of the sun. Would that  have technically been an OK thing to do, the lens seemed to be spot-on the infinity mark for 200 but would the practical focus change over 30 mins or so?
Title: Re: Filter for direct sun photography
Post by: nubu on November 25, 2011, 08:47:49 AM
Hi!
I also use the Baader filters http://www.baader-planetarium.de/sektion/s46/s46.htm that can be cut in all sizes for use IN FRONT of eyes, lenses and telescopes...

Attached you find some examples of use on
1) EF 100-400 (no sunspots during that eclipse)
2) EF 500/4 (during sunrise with "solarpower" foreground)
3) same eclipse but later with the sun higher up, leading to colour change!
4) 6" telescope showing the now much more active sun a few weeks ago

Always EOS 7D or 5DII...

With such a protection view and makeing pictures are save!!!

Cheers
Franz
Title: Re: Filter for direct sun photography
Post by: lol on November 25, 2011, 12:41:13 PM
The commonly available H-alpha photographic filters are NOT for photographing the sun. They're primarily intended to be used with deep sky objects. You need a much narrower bandwidth than the deep sky H-alpha filters to do that. Look at the dedicated solar scopes for an idea. I have an entry level H-alpha filter at 12nm bandwidth which I also tried with the sun just to see what happens. It doesn't resolve any detail you don't already get without the filter. The narrowest one of that type I've seen is 3nm. A dedicated filter in a solar scope is 0.1nm or less. You need it to filter out the other stuff and only look at the sun's H-alpha.

So unless you do go for the dedicated setup for the sun, you might as well go cheap with the reflecting filters for safety.
Title: Re: Filter for direct sun photography
Post by: TexPhoto on November 25, 2011, 02:49:57 PM
Shooting video of the sun with my 400mm f2.8 has not damaged my sensor at all, and most of us have included the sun in a photo from time to time without effect on the sensor.

Eyes on the other hand do deserve more protection. I use a welding shield I have, and can stare at the sun all day long.
Title: Re: Filter for direct sun photography
Post by: epsiloneri on November 26, 2011, 03:38:57 AM
I had a play around with various focus options yesterday taking a few test shots with manual / AF and viewfinder / liveview. Apart from liveview / contrast detect AF which was a dodgy as usual I didn't find much difference between all of them, so ended up just taking an initial phase-detect focus on the center AF point making sure it was on the edge of the sun. Would that  have technically been an OK thing to do, the lens seemed to be spot-on the infinity mark for 200 but would the practical focus change over 30 mins or so?

If you change nothing else, the focus should stay fairly constant (it can change if e.g. temperature or humidity changes appreciably). For accurate focus I use live view with magnification and manual focus. Phase detection can be a bit challenging sometimes in difficult conditions, but if it worked for you, then fine.

I would highly recommend you to attempt to catch the 2012 total solar eclipse, it's much more impressive and a completely different experience that does not compare to a partial eclipse!
Title: Re: Filter for direct sun photography
Post by: epsiloneri on November 26, 2011, 03:42:31 AM
I also use the Baader filters http://www.baader-planetarium.de/sektion/s46/s46.htm that can be cut in all sizes for use IN FRONT of eyes, lenses and telescopes...

Very nice Franz, in particular the one in front of the power station! I looked at your link, the films seems to have quoted neutral densities between 3.4 and 5. That seems a bit low, are you using multiple layers? Are the quoted numbers photographic stops or magnitudes?
Title: Re: Filter for direct sun photography
Post by: epsiloneri on November 26, 2011, 03:48:25 AM
Shooting video of the sun with my 400mm f2.8 has not damaged my sensor at all, and most of us have included the sun in a photo from time to time without effect on the sensor.

You have shot the sun with a 400/2.8 with video without a filter at all? Without destroying your sensor? I have a hard time believing that, and I will not be tempted to prove you wrong by trying it out myself... ;)
Title: Re: Filter for direct sun photography
Post by: nubu on November 26, 2011, 06:07:50 AM
I looked at your link, the films seems to have quoted neutral densities between 3.4 and 5. That seems a bit low, are you using multiple layers? Are the quoted numbers photographic stops or magnitudes?

ND 5 (17 apertures) is for visual work, ND 4 (13 A) for photography to give you short exposures. One may combine these filters with one of their solar continuum filters to have higher contrast:
http://www.baader-planetarium.de/sektion/s37a/s37a.htm. For Visual work I use the ND 4
plus a narrow band continuum. Its very nice and save since they all have IR/UV blocking.

I used the later for the detail pic with the 6" telescope shown above...

Franz
Title: Re: Filter for direct sun photography
Post by: TexPhoto on November 26, 2011, 10:30:10 AM
Shooting video of the sun with my 400mm f2.8 has not damaged my sensor at all, and most of us have included the sun in a photo from time to time without effect on the sensor.

You have shot the sun with a 400/2.8 with video without a filter at all? Without destroying your sensor? I have a hard time believing that, and I will not be tempted to prove you wrong by trying it out myself... ;)

Take a look at my video from about 0:28 - http://www.youtube.com/watch?v=hUp7fmM2wY0 Have shot similar scenes 10-20 times with 5DII and 7D.  Think about it though.  If the sun was going to damage your sensor, it would do it with a 50mm, or a fisheye.  It would just damage a smaller area.  And an f1.4 50mm would put a much brighter if smaller spot on the sensor tan a 400 f2.8.  And again we all include the sun in a photo from time to time, and I'm sure those who shoot video do so with video.  And yet there are not 1000s of reports of sun damaged cameras out there.

The only light source I've ever heard of damaging a DSLR sensor is lasers, typically at concerts/ laser light shows.
Title: Re: Filter for direct sun photography
Post by: dr croubie on November 27, 2011, 12:44:05 AM
I still blame the sun for the dead pixels on my 7D, it was just after I took photos of the eclipse of 04/01/2011 that I noticed all the dead pixels. Was with my 70-300 non-L and 15-85, at 300mm and 85mm, so both f/5.6 for framing but f/18-22 for the pics, some at f/36, speeds from 1/640s for the wide-shots but 1/2500-6400s for the 300mm shots.
I started off with the viewfinder but gave up after half a second and moved to live-view, I tried to keep my finger on the DOF-preview button but couldn't always. If I had an ND, that would have been when to use it, but I didn't at the time.
It was 2 weeks later doing long-exposures that I noticed the dead spots and put my camera in *3* times for warranty-fix (took them that many times to actually get rid of them all). I've just had another look, and I can even see the dead pixels in high-iso shots I took that night after the ecplise, and I can't see them in night shots taken a week before.

So yeah, I'm not pointing my camera at the sun ever again, without a pinhole or 20+ stop ND. Feel free to do it to your own camera though...
Title: Re: Filter for direct sun photography
Post by: PeterJ on November 27, 2011, 02:37:35 AM
One interesting thing as a side-note is that after the filter first arrived I took a a snap as above, minus the eclipse and the histogram wasn't like anything I'd seen before:

(http://i44.tinypic.com/x6kbqg.jpg)

I was expecting the peaks to be evenly spaced, I wondered if the filter and/or lens was doing anything funky but it does much up well with the Wikipedia "color vision" article that has a diagram showing human eye response:

(http://upload.wikimedia.org/wikipedia/commons/thumb/0/04/Cone-fundamentals-with-srgb-spectrum.svg/287px-Cone-fundamentals-with-srgb-spectrum.svg.png)

Still the peaks seem to drop off more rapidly, I guess just a sensor limitation where the silicon / bayer filter response doesn't match the eye exactly? It looks pretty predictable so I thought that might have been the sort of thing that would be corrected, although that was a RAW import into lightroom so maybe it does happen during the display and/or export stages?
Title: Re: Filter for direct sun photography
Post by: nubu on November 27, 2011, 04:23:02 AM
Never unfiltered Live-View with sun in the field of view, especially when on tripod!!! Normal exposures (no tele..) are no problem. Its the longer exposure time (the shutter does not close with live view) that kills the pixels...
Title: Re: Filter for direct sun photography
Post by: Fleetie on November 27, 2011, 02:23:35 PM
One interesting thing as a side-note is that after the filter first arrived I took a a snap as above, minus the eclipse and the histogram wasn't like anything I'd seen before:

(http://i44.tinypic.com/x6kbqg.jpg)

I was expecting the peaks to be evenly spaced, I wondered if the filter and/or lens was doing anything funky but it does much up well with the Wikipedia "color vision" article that has a diagram showing human eye response:

(http://upload.wikimedia.org/wikipedia/commons/thumb/0/04/Cone-fundamentals-with-srgb-spectrum.svg/287px-Cone-fundamentals-with-srgb-spectrum.svg.png)

Still the peaks seem to drop off more rapidly, I guess just a sensor limitation where the silicon / bayer filter response doesn't match the eye exactly? It looks pretty predictable so I thought that might have been the sort of thing that would be corrected, although that was a RAW import into lightroom so maybe it does happen during the display and/or export stages?

I don't think you're comparing like with like. The x-axis on your photo histogram is NOT frequency/wavelength. But it is on the spectrum from wikipedia. There is no reason why the graphs should match. As I understand it, the histogram's x-axis is "pixel intensity (black at the far left, and saturated/maximum at the right)", and the y-axis is "number of pixels at this intensity".

But if I have misunderstood what you were saying, forgive me.