Snow - over or underexpose

aberal

aberal

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Alan
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So what's the thinking of shooting in the snow? Do you overexpose to compensate for all the light being reflected from the snow and so pick up detail in buildings/trees etc and risk blowing out the snow itself? Or do you underexpose to pick up the detail in the snow itself and risking turning it grey? I've never figured this one out properly.
 
I think the theory behind it, is if correctly exposed, then everything should be correctly exposed. But you'll always need a bit of compensation to get that correct exposure in the first place.

It did get my brain ticking over yesterday, I have to admit.
 
I over expose by +1 to take away the harsh gray colour that snow can give off.
 
On a sunny day meters will usually give an accurate reading. On a dull day they tend to see the snow brighter than it is so underexpose. Increase exposure by 1 stop or a bit more. Bracketting is your friend.
 
Actually try correctly exposing for your subject. If that is the snow itself then meter from the brightest part in which you wish to retain detail and then open up by 2 stops, then check the histogram to see if some further modification is required as depending on your sensor you may want to open up a little further.

If your subject is not the snow itself, then meter from your subject and adjust the exposure to allow those tones to fall correctly, if this causes the snow to be under or over exposed, you have to either live with it or use some other means of balancing the light (flash, reflector, graduated filters, HDR). If not, you run the risk of your subject being a silhouette.
 
Whether under sunny skies or grey skies snow should usually appear pretty bright. Personally I would use manual exposure and spot meter off the snow and set an exposure to get the snow well over to the right of the histogram. Here are two examples. Note how the histograms look....

Grey skies (I did add +0.3 to the exposure in Lightroom)....

20101128_145224_.JPG


Sunny skies (no edits)....

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As I shoot raw with a Canon I would be looking to spot meter the brightest important area of the snow, or scene, at +3 stops or close to it. I believe for Nikon shooters the figure to aim for would be more like +2.3 stops. If you shoot to JPEG you might need to ease off by 1/3 of a stop or so, depending on how you have your in camera processing set up. Either way, that's a good starting point. If in doubt fire off a test shot and check the histogram and adjust to taste. Once you have your exposure locked in manually you are free to adjust your composition without fear of the exposure being thrown off.
 
Thanks for that everyone....need to put some of that into practice now.
 
EdBray said:
Actually try correctly exposing for your subject. If that is the snow itself then meter from the brightest part in which you wish to retain detail and then open up by 2 stops, then check the histogram to see if some further modification is required as depending on your sensor you may want to open up a little further.

If your subject is not the snow itself, then meter from your subject and adjust the exposure to allow those tones to fall correctly, if this causes the snow to be under or over exposed, you have to either live with it or use some other means of balancing the light (flash, reflector, graduated filters, HDR). If not, you run the risk of your subject being a silhouette.
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That, for me, was the most concise, and informative information I have seen for photographing snow.

Just asked my boss if I can leave at 3pm to test it out....:D
 
As Ed says, expose for your subject first. Watch out for nasty overexposure though, I personally prefer to have grey snow which I can then whiten in Photoshop, than no detail in it at all.
 
Is this not where a grey card comes in handy? Im sure iv read about it in a book but cant remember the details.
 
Blessed with snow overnight, here are sample shots taken by spot metering off the snow on the lawn at 0, +1, +2 and +3. As you will note, without correction the snow has been rendered as a grey tone and there is a lot of detail lost in the shadow regions. The shot at +2 probably has the optimum appearance, and the most realistic, and has prevented loss of detail in the shadows. However, as a raw shooter, shooting at only +2 I have wasted a stop of dynamic range at the highlight end that I could have made use of. The shot at +3 makes use of that unused capacity, even though the resulting image looks overbright. Nonetheless, I have not lost any detail in the snow and with my raw editor I can adjust the image as I see fit....

(Had this been a sunny snow scene I would definitely have wanted the brightest parts of the snow to be at +3, recording them as very white, but still holding nuances of detail.)

Shot with the snow metered at +0. A lot of shadow detail has been lost and my "white" snow looks grey....

20101130_083628_.JPG



Shot with the snow metered at +1. An improvement, but still the snow is grey rather than whote and there are still some signs of clipping in the shadows...

20101130_083725_.JPG



Shot with the snow metered at +2. There is just a hint of shadow clipping, which is not significant, but the shadowy areas are not showing details well....

20101130_083809_.JPG



Shot with the snow metered at +3. Observe that without losing any detail in the highlights this exposure has picked out far more detail in the plastic cover over the garden seat and in the foliage on the left near the camera. This exposure has maximised the dynamic range potential of the camera and pulled out more shadow detail with the minimum of noise...

20101130_083907_.JPG



Just to illustrate the power of raw, here is a shot taken at +4, which of course made the scene ridiculously bright and overexposed, but with a little manipulation it's quite possible to recover a usable image. This is not a stunt you can pull when shooting to JPEG...

20101130_091128_.JPG
20101130_091709_.JPG
 
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Tim, any chance of a 100% crop of the area under the bench of the +4 stop shot, I suspect it may have a bit more noise than the +2 stop shot of the same area.

I agree with you though as matter of course on film I would shoot at +2 stops metered off the brightest snow in which I wanted to retain detail, but with digital (and raw), I would use the histogram to give me as much dynamic range as possible.

Can't do my own shots, no snow here yet!
 
EdBray said:
Tim, any chance of a 100% crop of the area under the bench of the +4 stop shot, I suspect it may have a bit more noise than the +2 stop shot of the same area.
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Ed, I'm not with you on that. Why would there be more noise in the shot that was exposed 2 stops brighter? Remember, I am not pushing the files; these are individual exposures each doubling the exposure time of the predecessor. Anyway, here are crops....

Shot exposed with the snow at +2 (unedited except WB)....

20101130_082852_3816_LR.jpg



Shot exposed with the snow at +3 (unedited except WB)....

20101130_082854_3817_LR.jpg



Shot exposed with the snow at +4 (unedited except WB)....

20101130_082856_3818_LR.jpg



Shot exposed with the snow at +4 (and pulled back to make it look about right)....

20101130_082856_3818_LR-2.jpg



Forgive lack of sharpness. These were shot through double glazed patio doors that are in need of cleaning and my focus point was well beyond the bench. Handholding at 1/15 on that last shot probably didn't help much either for scrutiny at 100%.
 
Yes, sorry my mistake! Had a numpty moment there.
 
EdBray said:
Yes, sorry my mistake! Had a numpty moment there.
Click to expand...

So long as it wasn't a senior moment. :)

Just for completeness I thought I'd repeat the test, but shooting to JPEG with the Standard picture style. Here are the results....

Snow metered at +0....

20101130_124402_.JPG



Snow metered at +1....

20101130_124440_.JPG



Snow metered at +2....

20101130_124509_.JPG



Snow metered at +3. Now we see signs of clipping, which is not desireable in a JPEG, but in this case is not criminally severe. Shooting about 1/3 stop dimmer should probably fix the problem....

20101130_124548_.JPG



Snow metered at +4. Now there is widespread highlight clipping and this file is beyond redemption....

20101130_124620_.JPG



Snow metered at +4 and then edited with a -4 exposure adjustment in Lightroom. As you can see, much of the detail in the snow has been lost for good. You could make the snow look grey rather than white, but you will not recover the details that the JPEG conversion in camera has destroyed. Where the raw version of this file was salvageable, the JPEG equivalent is toast. I've disabed the highlight clipping warnigs just so you can see how much of the snow has been turned into a featureless white mass....

20101130_124916_.JPG



By the way, while the snow will often be the brightest part of your scene, you may find at times that (parts of) the sky is even brighter, so if you want to avoid blowing the sky you will need to consider metering from the sky rather than the snow, or whatever is brightest within the scene for which you want to retain detail in texture or colour. Either way, spot metering from the brightest area at between +2 and +3 (on a Canon camera) should get you in the right ballpark. On a Nikon you might need a little less. With other brands I don't know how the metering is set up.
 
Thanks for the test shots Tim and certainly brings home the benefit of shooting in RAW. However was there any particular reason you chose the 7D over the 5D2 for this comparison ?.
 
Roguet said:
Thanks for the test shots Tim and certainly brings home the benefit of shooting in RAW. However was there any particular reason you chose the 7D over the 5D2 for this comparison ?.
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Yes. I was originally going to shoot the demo with autoexposure and exposure compensation and the 7D offers +/-3 stops of EC where the 5D2 only offers +/-2.

However, as soon as I came to shoot, and wanted to frame without the spot meter in the centre, necessitating use of exposure lock, I was reminded what a complete faff autoexposure was and reverted to my preferred technique of shooting manual. Far easier all round, and of course the 5D2 would have been fine for that, but I already had the 7D in hand so that was what I used. For the purposes of the demo it really didn't matter which camera I used. Had I been shooting a scenic image for real then I would have used the 5D2, but IQ, composition/FOV and aesthetics were not the consideration here, only a demo of metering and exposure for snow scenes.
 
Hi Alan
The exposure meter in your camera reads the light being reflected back from whatever you are photographing and is designed to give you a reading that represents a mid grey colour. This works well in most situations but when you have the light reflecting off snow your camera takes a reading to give a mid grey colour and that is what you are getting so will need to give more exposure so that your white does indeed turn out white.The same goes for the other way round of course if it is very black it will take your exposure and make it grey so you would need to underexpose to get your black.

All these relective exposure meters use the same system, so there is an inexpensive bit of kit available about £12 called a 18% Grey Card (this is the same mid grey colour the camera is measuring) So you take out your grey card take a meter reading from this and the exposure should then be ok.

Hope this info is of use Regards Jim
 
As someone who learnt on film I agree with Tim that manual exposure is the way to go.

However if you do shoot on one of the semi-auto settings (PASM) you need to know that your camera may adjust the reading it gets because it realises that you are probably shooting a snow scene.

I know that my camera will make an adjustment if I am using Matrix metering but does not adjust if I use Centre or Spot.

I have just tried it out (as an ex-engineer I know that theory often has to be adjusted to match up with what really happens :))

I used Aperture Priority for all the shots.

With Spot I got grey snow all the time, all of the histogram was left of centre.

With Matrix I got white snow sometimes and grey snow at other times, it seems to depend on what is in the scene. If it is just snow it comes out grey, if there is someting else, such as trees or bushes, the snow comes out white(ish). It probably adds one stop to the exposure.

It really does seem to be a case of checking the histogram and adjusting to suit.
 
There's another point to all this and that is that there is not necessarily a single "correct" exposure. The "correct" exposure is whatever you want it to be. If you want dazzling white snow you can achieve that. If you want regular white snow then that's possible too. If you want grey snow then you have that option. If you are shooting at dusk, or exclusively in the shade, then maybe you will purposely want to render the snow as greyish rather than bright white. If you are shooting in bright sunshine then you will surely want the sunlit patches of snow to look dazzling, and anything but grey.

It's up to you to set the camera up to achieve the exposure you want. If you don't like what the camera is giving you then change it.
 
tdodd said:
It's up to you to set the camera up to achieve the exposure you want. If you don't like what the camera is giving you then change it.
Click to expand...

Isn't this called previsualisation?
 
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