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04/13/2006 03:52:59 PM · #1 |
I want to take a photo of the moon. But I want to try to make it similar as star trails and have a trail. But unfortantly the lens I am using can only stop down to f32. And even with an iso of 100 the longest exposure I can get without over exposing is around 30 to 45seconds. So is there a filter or something I can use that will just reduce the amount of light entering the lens. My polorizing filter does this but only about 2 f stops. I was hoping for something closer to 10 fstops or more. Thanks guys
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04/13/2006 03:55:51 PM · #2 |
You want the moon and star trails in the same shot? Or you want the moon to leave a trail during a long exposure?
The filters you're talking about are called "Neutral Density Filters" (ND) and they come in many degrees of opacity. They won't help you with the first example (the moon is too much brighter than the stars) but they will allow you to increase your exposure time dramatically so you can, in fact, show the moving moon. The result, however, will just be a smear of light, you knwo that right?
R.
Message edited by author 2006-04-13 15:56:36.
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04/13/2006 03:56:25 PM · #3 |
| Nutral density filters do this, but you'l probally have to stack them because i dont think i ever seen one that goes over 5 stops or so. |
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04/13/2006 04:09:30 PM · #4 |
Here's a great little ND Filter! You dial the density...one piece of glass and it screws on!
//www.singh-ray.com/varind.html |
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04/13/2006 04:15:28 PM · #5 |
| There are specialized ND filters for shooting the sun during eclipses. I believe it's about 15-19 stops. It's spendy though for something you'll hardly use. |
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04/13/2006 04:26:47 PM · #6 |
Wonderful filter, but $340-390 is REALLY steep... At least it's 77mm, so you can step it down to everything smaller...
R.
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04/13/2006 04:27:52 PM · #7 |
humm....thanks for all your replies. I guess this will just be one idea I will never follow through with. It looks like most ND filters don't go dark enough for what I need. And I don't like the idea of stacking lots of filtters together for obvious reasons.
To reply to a few comments first I knew I would lose the stars due to the diffrence in light. Second I knew it would be just a stream of light. I was hoping to get a photo of the moon moving through the sky over my home town.
Also that 380$$ filter someone posted. What I bet that is is two polorizing filters on top of each other. As you spin one it has the same effect as they show on that movie. But even that may not get dark enough.
Thanks for all your input. You anwsered my question :-)
Message edited by author 2006-04-13 16:29:08.
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04/13/2006 04:27:57 PM · #8 |
Originally posted by jent:
But unfortantly the lens I am using can only stop down to f32. And even with an iso of 100 the longest exposure I can get without over exposing is around 30 to 45seconds. |
If you want to shoot star trails, you'll need to shoot at about ISO100-ISO400 at around f4 to get anything like visible trails.
If you stick an ND in front of the lens you'll get no trails at all.
You might get a less 'overexposed' moon, but it will still be a streak across the scene - you won't see it as 'the moon' because it is moving throughout the exposure.
Typically for a sharp moon shot, you need to use a fairly fast exposure (sunny 16, opened up about a stop - it is a light coloured, sunlit object, after all) to get detail as it is moving quite quickly.
So for star trails, close to wide open for a long time, for the moon, quite stopped down and a fastish (>1/30s or so) shutter speed.
An ND won't help. IF you want a sharp image of the moon on a long exposure, with an ND, you'll need some sort of automatic object tracking tripod, which would stop you getting trails though (they exist for telescopes)
If you shoot the 'star trails' way, you'll get a really wide trail that was the moon (but obviously no 'moonlike' detail)
3 minute moon exposure
or you could take a fancy shot like this. How it was done is left as an exercise for the viewer ;)
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04/13/2006 04:28:41 PM · #9 |
Originally posted by Bear_Music:
Wonderful filter, but $340-390 is REALLY steep... At least it's 77mm, so you can step it down to everything smaller...
R. |
Couldn't you do the exact same thing with two linear polarizers if you were willing to forgo the autofocus? |
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04/13/2006 04:30:33 PM · #10 |
Originally posted by jent:
humm....thanks for all your replies. I guess this will just be one idea I will never follow through with. It looks like most ND filters don't go dark enough for what I need. And I don't like the idea of stacking lots of filtters together for obvious reasons. |
Most of the IR only/ IR band pass filters are also effectively a 10 stop ND. One of those might work (though I wonder if the moon really reflects much IR to earth for it to show up...) |
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04/13/2006 04:31:11 PM · #11 |
Originally posted by DrAchoo:
Originally posted by Bear_Music:
Wonderful filter, but $340-390 is REALLY steep... At least it's 77mm, so you can step it down to everything smaller...
R. |
Couldn't you do the exact same thing with two linear polarizers if you were willing to forgo the autofocus? |
I suppose so, though there'd be a vignetting effect to deal with, and the "minimum" effect would be probably still too dark for good focusing...
R.
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04/13/2006 04:37:01 PM · #12 |
| Could you no do it with a black card? Expose it for what you need to get a clean shot (or whatever you are after), put the black card in front of the lens for some period of time and then repeat. Would be hit and miss until you timed everything but might work - and it's pretty cheap. |
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04/13/2006 04:40:41 PM · #13 |
Originally posted by robs:
Could you no do it with a black card? Expose it for what you need to get a clean shot (or whatever you are after), put the black card in front of the lens for some period of time and then repeat. Would be hit and miss until you timed everything but might work - and it's pretty cheap. |
this is a great idea....i may try something like this
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04/14/2006 04:41:56 AM · #14 |
| It's possible to use two polarising filters. With the direction of polarisation on the one at ninety degrees to the other, you sort of polarise out everything. As you approach ninety degrees, the effect is gradually darker, so you can play around with it. |
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