Questions on using Exposure Compensation

[michaelxjw]

I am scheduled for a cruisetour to Alaska next month and am using a Nikon D5100 camera with the Nikon 18-105 VR and Tamron 70-300 VC lenses. Since I will be viewing glaciers from a cruise ship on my vacation, I have a question regarding exposure compensation:

 

I understand that you generally must apply positive exposure compensation when viewing glaciers, particularly when viewing from a cruise ship over water. Are there any general rules for how much positive exposure compensation to apply for best results; i.e., 1/3 stop, 2/3 stop, 1 stop or more? Also, would these guidelines be different depending upon the weather conditions, such as overcast vs. a bright sunny day? Thanks for your advice.

 

Michaelxjw

[awboater]

If you take a photo of a complete white wall, it will turn out grey, as the camera will generally underexpose it by a full 2 stops.

 

Or if you take a photo of a complete black wall, it will turn out the same identical color grey, and the camera will overexpose by 2 full stops.

 

This is what you have to work with.

 

Usually this is only a problem when a significant amount of the photo is white or black; perhaps 80% or more - such as on a beach, snow, etc.

 

But if you have significantly less than 100% white or black in the scene, the underexposure or overexposure will vary accordingly - if at all, so I am not sure there is a universal rule of how much compensation to use. You will have to constantly judge the amount.

 

An alternative I think I would use, is to change the camera from matrix to spot metering (and you may have to change the focusing to spot as well), then use the selector to select the part of the scene you want properly exposed. That way, no matter how much white background, grey skies, etc you will get the intended exposure.

 

Or, learn how to use the AE-Lock (if your camera has one) and recompose. If your camera does not have such a lock, you might be able to program your shutter button's half-way down position to lock auto exposure.

 

As a general rule though, I like to use about a -1/3 underexposure in all of my photos as a slight underexposure seems to bring out colors a bit - especially the blue sky. So my cameras are all setup with a -1/3 stop exposure compensation for everything.

 

Of course, the thing is to practice with any such changes you make until you are comfortable with them before going on your cruise. You don't want to wait for the breathtaking photo to experiment.

[TheOldBear]

If you set the camera to capture images in 'raw' mode, it _may_ be possible to recover, when processing in a computer, some detail that the camera's JPEG conversion will drop [so called 'blown highlights']

 

If you are in the same light as your subject, you can approximate an incident light reading by using a neutral grey card [or even the palm of your hand, your palm is about one stop brighter than a standard neutral grey card].

 

You may also want to 'bracket' your exposure [shoot one stop smaller and one stop bigger than the basic metering suggestion]

 

Remember - the standard metering for a camera tries to make the output image average as an 18% neutral grey. If that does not describe the scene, then you will need some degree of manual input to make the exposure somewhere in the range that the camera can capture.

[the_journeyman]

RAW can help, you can make slight exposure adjustments with raw.

 

When in doubt, shoot multiple frames at different exposures. I usually go with the light meter, but also take into consideration where my spot meter is metering. It'll read very different in the same light when spotting on a dark subject versus a light subject. I look for a more neutral color if possible, and use the AE lock Bear mentions then recompose the frame how I want it.

 

I usually shoot in manual mode anyway, so 3-4 frames stopped up or down is simple.

 

JM

[havoc315]

You've gotten great advice in this thread.

Outside of exposure compensation, some things that really work:

 

-Use bracketed exposure. That will give you 3 different exposures to choose from. And also the possibility of merging them into HDR, to truly preserve the highlights and the shadows.

 

- Use spot metering and AE-lock. I'll sometimes spot on the sky, and lock the exposure there. That way my sky is always nice and blue. Otherwise, I find my skies get over-exposed. In your case, metering on the glaciers would likely lead to under-exposure.

 

-Shoot in RAW. With the warning that your images won't look as good straight out of camera, but will look much better with tiny post-processing tweaks, including much much more freedom to really adjust exposure in post-processing. (When I don't spot meter on skies, I'll often adjust the RAW with a graduated filter to save the sky).

[framer]

Does the 5100 have a histogram? I tend to check that and make adjustments with that info.

 

framer

[seadancer]

It does hard to find though. You have to take a pic and look at it on the LCD and then there's a menu from there in the picture edit section

[pierces]

Rule of thumb is overexpose +1 for bright sandy beach/desert or snow. Metering tries to make everything average out to medium 18% gray, which works out in most scenes. If you scene is predominantly white, the average places the white snow aat a point closer to grey and the scene looks "muddy".

 

As was mentioned, bracketing is a good insurance. I would bracket at +.5, +1 and +1.5 for glacier scenes with a lot of white in them. If it is overcast, you will have to overexpose considerably less.

 

Some camera's scene modes include a "Snow" or "Beach" setting which has the exposure bias built in.

 

If all else fails;shoot, chimp and adjust until you see what you like on the LCD!

 

Enjoy your trip!

 

Dave

[michaelxjw]

Thanks Pierces

 

This is exactly the type of "guidelines" I was looking for. My camera has both a Snow/Beach Scene mode and an Exposure bracketing function. I will try both in addition to applying your guidelines (not necessarily at the same time!)

 

Michaelxjw