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Occasional Contributor
Posts: 5
Registered: ‎08-03-2017

solar filter

Ok...I am new to this and dont really know much but I have a canon rebel t5 and I am going down to TN to try my hand at photographing the eclipse. I bought a filter to fit my camera and dont know what 18 stop means. Can anyone enlighten me?

Respected Contributor
Posts: 1,771
Registered: ‎02-17-2016

Re: solar filter

[ Edited ]
Occasional Contributor
Posts: 5
Registered: ‎08-03-2017

Re: solar filter

Thank you sir.

 

Esteemed Contributor
Posts: 2,929
Registered: ‎06-11-2013

Re: solar filter

18 stops seems an odd number... but it'll work.  

 

Most solar filters are "ND 5.0".  ND means it's a "neutral density" filter and the "5.0" is the density value.  Each "0.1" worth of density is exactly 1/3rd of a photographic "stop".  So "ND 0.3" would be just one photographic stop.  ND 0.6 would be two photographic stops, ND 0.9 would be 3 photographic stops, etc.  And by that math... ND 5.0 is actually 16 and 2/3rds of a photographic stop (just shy of 17 stops).  

 

The "stop" means it cuts the light exactly by 1/2.  So a 1-stop filter cuts light transmission through the filter so that only half of it can pass through.  A 2-stop filter means it's 1/2 of 1/2... or a total of 1/4.  A 3-stop filter is 1/2 of 1/2 of 1/2 (or 1/8th of the light can pass through).  

 

For an ND 5.0 filter, it means only one photon of light out of every 100,000 can pass through (it blocks 99.999% of the light).  If you were to attempt to hold the filter between you and ... say a desk lamp... you wouldn't be able to see any light from the desk lamp (it isn't nearly bright enough).  

 

Remeber that you only use the filter BEFORE or AFTER totality.  DURING totality you may look directly at the Sun (and your camera can directly photograph the sun without any filter).    It is the only time it is safe to look at the sun without proper protection.

 

Also... if the camera is on a tripod, you'll need to nudge the composition along to keep up with the apparent movement of the Sun & Moon (since the Earth is spinning).  You should do a final check of your framing and focus about 1-2 minutes before totality begins but do this WITH the filter still on the camera.  You may remove the filter about 20 seconds before totality (and no sooner than 50 seconds before totality).  Once totality ends, you should put the filter back on the camera at 20 seconds after totality.

 

The reason for removing the filter those few seconds before totality is because the "diamond ring" effect is usually visible about 9 seconds prior to totality and the "baily's beads" effect is usually visible about 1.5 seconds before totality.  You would want the filter off to photograph those.  Both of these repeat after totality ends but the effects would be completely over within 20 seconds of the end of totality.

 

You can find exposure guidance here:  http://mreclipse.com/SEphoto/SEphoto.html

 

 

Tim Campbell
5D III, 5D IV, 60Da
Honored Contributor
Posts: 7,780
Registered: ‎12-07-2012

Re: solar filter

" I bought a filter to fit my camera ..."

 

What lens?  If you got it for the standard Rebel kit lens, you will not get a very good shot of the Sun.  The Sun is the same size as the Moon so you might try a few shots of it before to see what you may expect.

A lot of Canon stuff. Along with, a lot of other stuff.
Esteemed Contributor
Posts: 4,862
Registered: ‎08-13-2015

Re: solar filter

[ Edited ]

ebiggs1 wrote:

" I bought a filter to fit my camera ..."

 

What lens?  If you got it for the standard Rebel kit lens, you will not get a very good shot of the Sun.  The Sun is the same size as the Moon so you might try a few shots of it before to see what you may expect.


Taking a few shots of the Moon is a good idea.  It gives you a chance to practice focusing, because the focus for the Moon will be ideal for the Sun.  It also gives you practice at working in the dark, as well as, a chance to rehearse what you want to do during Totality.  You should figure out all of that stuff ahead of time.  Find out how long it will last, too.

 

I hope you have a robust, professional grade tripod.  They don't sell them at the Big Blue box stores, just plastic ones that shake and break.  When you use longer focal lengths, any camera shake becomes magnified, so a good stable platform is a must. 

 

Another "must have" is a remote shutter, so that you don't have to touch the camera to fire the shutter.  Using the camera's built-in 2-10 second shutter delay works, too, but  you may miss "the moment" of the diamond ring because of the delay.

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"I don't rent software. I use Photoshop CS6, ACR 9.8 and Lightroom 6.8 ."
Occasional Contributor
Posts: 5
Registered: ‎08-03-2017

Re: solar filter

I bought a 5.4 18 stop filter from Firecrest Filters Formatt Hitech. I bought this camera to photograph the sun and I also bought a tripod from Orion designed to hold a camera with a equatorial motorised tracker. And any advice I could get between now and then is greatly appreciated.

Occasional Contributor
Posts: 5
Registered: ‎08-03-2017

Re: solar filter

Thank you for your input. I bought a Canon EF 75-300mm 1:4-5.6 III. I have been shooting the moon for practice and got the stacking software and have some pretty good shots so far. I have been practicing on the sun hoping to catch the sun spots but havent stacked them yet. Now I am hoping you are going to tell me it is at least adequate.

Esteemed Contributor
Posts: 4,862
Registered: ‎08-13-2015

Re: solar filter

[ Edited ]

Lloyd_Welch wrote:

Thank you for your input. I bought a Canon EF 75-300mm 1:4-5.6 III. I have been shooting the moon for practice and got the stacking software and have some pretty good shots so far. I have been practicing on the sun hoping to catch the sun spots but havent stacked them yet. Now I am hoping you are going to tell me it is at least adequate.


That lens is a good starter lens.  Avoid the low value f/stop settings, which means the aperture is opened wider.  You will get better results at f/8, with the aperture stopped down a bit.  Practice on the Moon, too. 

 

Use ISO 100, the lowest setting, as much as practical.  Of course, that should mandate a tripod.  Look at the Benro brand from online retailers like B&H and Adorama.  Avoid eBay and Amazon like the plague.  The only thing I would consider buying from those vendors are paperback books.

 

[EDIT]  You should figure on spending $150-$250 for a quality tripod, not unless you catch one in that price range on discount.  You want one with a decent load capacity, for added stability when you raise the center column.  You will get the most stability, and the best images, with the center column lowered to its' minimum height.  I recommend a tripod/head combo that can support at least 15 pounds for a T5 and the EF 75-300mm combo.  

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"I don't rent software. I use Photoshop CS6, ACR 9.8 and Lightroom 6.8 ."
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Honored Contributor
Posts: 7,780
Registered: ‎12-07-2012

Re: solar filter

"I bought a Canon EF 75-300mm 1:4-5.6 III."

 

IMHO, 300mm is too short.  Way too short. Again, IMHO, 400mm is minimum focal length and 600mm is a whole lot better.

But if it is giving you what you want, fine. 

 

You do not need to track the Sun eclipse or the full Moon. Exposures will be fast enough.

A lot of Canon stuff. Along with, a lot of other stuff.
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