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Super Contributor
Posts: 215
Registered: ‎01-27-2018

How to take photos of the blood moon?

Hi All,

 

Wondering if anyone seen the moon of late? Not sure if it has anything to do with the fires near by, but the moon certainly look amazing. That said, I am curious what would be the best setting to take photos of the moon? I've tried manual as well as auto settings, nothing seems to work properly. I am using the 5Ds and 20-700 MK2.

 

Thanks,

LV

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Registered: ‎12-07-2012

Re: How to take photos of the blood moon?

The place to start is the Looney 11 Rule.  It says with f11, SS 1/100 and ISO 100 you will get a good Moon shot. Of course it is just a starting point.  As always you should bracket each way several stops.  Bracketing is your friend.

EOS 1DX and 1D Mk IV and several lenses!
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Registered: ‎06-11-2013

Re: How to take photos of the blood moon?

There’s a basic guideline for shooting the moon... and there’s a more complex formulat that works out what happens when the moon (or any celestial object) is near the horizon.

 

First the basic guideline:  The Looney 11 Rule

 

That’s the real name... I didn’t make that up.  Looney being a play on Lunar.

 

Anyway, the moon is lit by the Sun.  And since the rule for daytime exposures (shooting any subject in full mid-day sun) is called the “Sunny 16” rule (if you use f/16, then you’ll get a correct exposure if you set the shutter speed to the inverse of your ISO setting.  E.g. at ISO 100 use 1/100th sec.  At ISO 200 use 1/200th sec, etc.

 

You’d think you could use that rule, but it turns out the moon isn’t highly reflective.  Only about 1/8th of the light that hits it (about 12%) reflects back.  It’s roughly the reflectivity of an old black rubber tired (turned gray) or a worn asphalt road (not fresh).  Also, you’re shooting thorugh the Earth’s atmosphere.  A typical subject we shoot could be anywhere from a few feet to a few miles of air between the camera at the subject.  For the moon, it’s the height of the entire atmosphere.  Dust particles, moisture, and other scattering effects slightly dim the moon and all in, you need to add just about 1 full stop of light (going from f/16 to f/11 is one full stop of aperture).

 

So the Looney 11 rule says that if you set the aperture to f/11, then you’ll get the correct exposure if you set the shutter speed to the inverse of the ISO (e.g. at ISO 100, use 1/100th sec.). Most people tend to over-expose the moon by trusting their camera.  The “problem” is the camera sees all the dark sky around the moon and assumes it needs to increase the exposure to find the details in all that blackness.  So really you want to exposure *just* for the disk of the moon (e.g. if you used spot metering on the surface of the moon only, you’d get a better exposure than you would if you let the camera use it’s default ‘evaluative metering’ which tries to sample most of the frame.

 

If I could offer one single piece of advice... it would be to (a) know the Looney 11 rule and (b) use “spot metering” to meter the disk of the moon.  

 

But be careful with (b) because that’s really only going to work well if your lens has a long focal length (short focal length lenses will meter more than the size of the sun itself and average in a lot of the background black sky resulting in an over-exposure.)

 

 

 

 

But you mentioned you thought possible the moon was a bit more red due to smoke or other effects that alter the transparency of the air.  This effect is called “extinction”.

 

The concept of “extinction” is simple... but the rules to determine it are very very complicated.  You can do a search for “atmospheric extinction” to find articles that will go into detail.

 

But the simple idea is this:  

 

If you are at sea level then the amount of air directly above your head (drawing a line straight up to the top of the atmosphere) is 1 air mass.  

 

If you were to draw a line at a 45° angle to the top of the atmosphere then you would be looking through at 1.4x air masses — you are no longer looking through the shortest possible distance to exit the atmosphere).

 

The atmosphere is mostly transparent... so this doesn’t really effects the exposure in any meaningful way (unless the air is really loaded with things making it less transparent ... dust, smoke, water vapor, etc.)

 

It turns out, if you had no trees or buildings on the land and had a perfectly flat view to the horizon... and looked at a “star” that was just at the horizon line... you’re looking through about 40 air masses (and that *does* add up in terms of impacting your exposure in a very noticeable way).

 

The complicated bit is that there no set rule in terms of how it impacts exposure because it really depends on the transparency of the air... and that varies.

 

If an object (such as the moon) is more than about 30° above the horizon, the effect is small.  But the closer it gets to the horizon, ithe faster it ramps up.  When an object gets below 10° above horizon, it starts to ramp up quickly... and below 5° it gets quite extreme (this is why, as the sun kisses the horizon at sunset, there’s a very noticeable difference in brightness from the bottom of the sun to the top of the sun and usually the sun is heavily distorted.)

 

 

Tim Campbell
5D III, 5D IV, 60Da
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Registered: ‎06-25-2014

Re: How to take photos of the blood moon?


@ebiggs1 wrote:

The place to start is the Looney 11 Rule.  It says with f11, SS 1/100 and ISO 100 you will get a good Moon shot. Of course it is just a starting point.  As always you should bracket each way several stops.  Bracketing is your friend.


Notwithstanding the Looney Rule, why would anyone ever use f/11 to photograph the Moon? You're focused at infinity, so depth of field is not a consideration, and the subject is moving (slowly, but at the highest magnification you can manage). So why wouldn't you use the widest aperture at which your lens can give decent results, in order to maximize the shutter speed? And why, with any modern camera, wouldn't you use an ISO setting at least three stops faster than 100? No doubt the answer is incorporated in "it is just a starting point". but the rule as stated sounds like an archaic relic of the Plus-X era.

Bob
Philadelphia, Pennsylvania USA
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Registered: ‎06-11-2013

Re: How to take photos of the blood moon?

[ Edited ]

This rule is the same as the Sunny 16 rule... a way to know the exposure without needing to use a light meter.

 

You don’t have to use f/16 for the Sunny 16 rule.  You don’t have to use f/11 for the Looney 11 rule.  But once you know the exposure... you can trade stops of aperture for shutter speed to use whatever you’d prefer.

 

Both rules are used because the simple inverse relationship with ISO... and given a catchy name so they’re easy to remember.

 

E.g. suppose you want to use f/8 ... at f/8 (one stop brighter than f/11) the inverse relationship doesn’t work.  The shutter speed at f/8 is actually the inverse of DOUBLE whatever the ISO is (e.g. at ISO 100, the shutter speed is 1/200th.  At ISO 200, the shutter speed is 1/400th).  And it’s the inverse of 4x at f/5.6, the inverse of 8x at f/4, etc.  Since those are a bit more confusing then the very simple inverse at f/11... the f/11 guideline is the easy way to remember the exposure ... and then just trade exposure stops to find the equivalent exposure.

 

Tim Campbell
5D III, 5D IV, 60Da
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Re: How to take photos of the blood moon?

"No doubt the answer is incorporated in "it is just a starting point"."

 

Yes it is Robert, and do not doubt the benefit and necessity of bracketing.  It is an exposure, in toto, that can be modified but it gives you the "starting" point.  

EOS 1DX and 1D Mk IV and several lenses!
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Registered: ‎06-11-2013

Re: How to take photos of the blood moon?

BTW, this pertains a little less for the moon (any exposure for the moon will not *also* contain stars) but for photos that *do* contain stars, there's a benefit to stopping down... at least a little.

 

This shot was taken using the Canon EF 135mm f/2L USM

 

The first image was shot at f/10 for 8 minutes:

 

IMG_2719.JPG

 

This second image was shot at f/2 but for 1 minute:

 

IMG_2741.JPG

 

Both images used ISO 800.  They aren't equivalent exposures (the first image was a test shot to test tracking - to take an 'equivalent' exposure would have required about 25 minutes and I wasn't going to wait that long) but what I really am trying to call attention to are the three brightest stars on the left side.

 

This is the lower half of Orion ... but rotated 90° CCW so it's on it's side.  

 

In the first image, the stars are sharp, but at f/10 we're getting noticeable diffraction spikes from the aperture blades.

In the second image, those brightest stars are a bit bloated and showing some saggital distortion.

 

Stopping down just a touch ... maybe to f/2.8 or f/4 ... would have really helpd reduce those distortions in the brightest stars (the dim stars don't have a problem.)

 

Tim Campbell
5D III, 5D IV, 60Da
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Re: How to take photos of the blood moon?

Very nice Tim. Smiley Happy  Very nice.

I sold my Canon EF 135mm f/2L USM some time ago in favor of the 85mm f1.2L.  Your shots make me want another 135mil.  They always were great lenses even way back in the FD days.

EOS 1DX and 1D Mk IV and several lenses!
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Posts: 215
Registered: ‎01-27-2018

Re: How to take photos of the blood moon?

Curious what focal length is best for taking photos of the moon? I used 70-200 @200mm and the moon came out pretty small.

 

Cheers,

LV

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Posts: 4,250
Registered: ‎02-17-2016

Re: How to take photos of the blood moon?

[ Edited ]

At least 400, more is better.

 

You can figure out for yourself how much of the area the moon will take up, since it is about 1 degree.

 

At 400 mm the field of view of a crop frame camera is about 3.8 degrees.

For full frame, 6.2 degrees

 

200 mm will double those fields of view.

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