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When I take pictures of objects in the sky (aircraft, birds, etc.), I frequently find that the entire sky looks underexposed. I typically take such pictures in Program mode ("P"), because there is often not a lot of time between hearing or spotting the object in question, rushing to get my camera, and aiming the camera to take a few shots before the opportunity passes. There is not a lot of time to fiddle with camera settings or make test exposures. I shoot through the lens and not with "live" mode and don't have any feature like a live histogram available.

I have seen this behavior with a variety of shooting angles relative to the sun. I would expect that as aim closer to the sun, any object I am photographing would become more backlit and in its own shadow and thus appear dark. But the entire sky seems dark, and I see this even when shooting with the sun at my back. In the pictures below you can see the parts of the aircraft facing the sun and in the shade but the sun lit side seems very dark to me in the "normal" (+0EV) exposure. I mainly this phenomena at telephoto lengths, making me suspect the lens, but since metering is through the lens I would expect that this shouldn't make a difference, at least not this much.

Typically, adding two stops to the exposure makes the shot better match my expectations. To me this seems like a lot, like the metering system is seriously misreading the scene, yet the scene does not seem that complicated. But am I expecting the wrong thing? Am I just expecting the picture to be too bright? Is there some obscure setting I am missing?

Here is an example. Both images shot on a tripod around 2p.m. on a sunny day at ISO 100 f/6.3 with a Nikon D5100, a Tamron 18-270mm f3.5-6.3 VC len at 270mm (VC off) as part of an exposure bracket (-2EV, 0EV, 2EV). Active D-Lighting is set to the highest setting. (This setting for Active D-Lighting has shown the brightest sky images in all my tests.) No other in camera adjustments. These pictures were taken with "multi-segment" metering, which if I understand correct is looking at a large part of the sky and so shouldn't be underexposing the whole picture.

1/1250s, +0EV, full image scaled to 25% enter image description here

1/1250s, +0EV, cropped image at full resolution enter image description here

1/250s, +2EV, cropped image at full resolution enter image description here

My understanding is that for security purposes the meta-data may be stripped by SE sites, but I can post any additional metadata needed (there are over 200 individual pieces, so I'm not posting it unnecessarily.)

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    Does this answer your question? Dark Image at longer focal (aviation photography) – Michael C Jan 16 at 7:34
  • Part of your problem is that the sun is high above. You make much better pictures with the sun in your back, and a bit lower on the horizon. From experience, I aim the camera to the part of the sky where the subject will be shootable, and wait for it to appear there (it usually does at some point). Fortunately, the more interesting planes are usually towards the end of the show, at the end of the afternoon. – xenoid Jan 16 at 10:32
  • @xenoid Yeah, I recognize the issues with the sun. If you're shooting at a show I imagine you have much better opportunities to get a good angle. – Michael Jan 16 at 19:13
  • Not that much... the public is parked in a specific area, and there are other photographers around you. However shows are normally over an East-West track with the public on the south side (our eyes are even more sensitive than our cameras). But a blue sky is an easier background than overcast/clouds. – xenoid Jan 16 at 20:55
  • Because metering assumes your scene is 18% grey, on average. The camera doesn't know that you're taking an image of an object that is brighter than things that aren't in the frame. The exposure looks dark to you because the sky is bright relative to other things but those things aren't in the frame so the camera doesn't know this. This is why typically white scenes (snow) are underexposed and dark scenes (night) are overexposed. In both cases you have to compensate with +/-EV to move the midpoint's tone to the right place. – Martin Krzywinski Apr 18 at 5:53
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The others have explained why the metering is causing issues, but I would like to add that active D-lighting actually underexposes the image in order to preserve highlights (~1 stop at max), and then processes the data/jpeg to restore midtones/shadows... IMO, it is not really helping you.

Personally, with the D5100 I would be shooting in manual mode for this subject/situation (in order to force lower shutter speeds) with auto ISO and matrix or CW metering (resulting in underexposure). And I would be recording raw files.

With the D5100 there is essentially no penalty to recording darker raw file images as long as it is done by using lower ISO's... The camera is very nearly entirely ISO invariant; so when the image is recovered in post it will look essentially identical to having used a higher/correct ISO. Except you can do selective recovery and retain the highlights if you want. http://photonstophotos.net/Charts/PDR_Shadow.htm#Nikon%20D5100 http://photonstophotos.net/Charts/PDR_Shadow.htm#Nikon%20D5100

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    Yeah, I'd turn off Active D-lighting (or the Canon equivalent: Highlight Tone Priority) as well. – Michael C Jan 16 at 19:33
  • Although I upvoted all the other answers that helped me (and some of them were very informative) I'm accepting this answer because I have found shooting in RAW and post-processing very helpful. Aircraft flying overhead often give little warning and I don't always have time to fiddle with the settings, and leaving it on +2EV just in case my next shot is of the sky often means I forget and overexposure a totally different type of shot. I've had good results bringing up the shadows in post using RAW when images do wind up looking too dark. – Michael Apr 15 at 20:41
  • Yeah, the D5100 supports 14-bits per color (RGB) vice only 8 in the processed jpeg so you have a lot more room to adjust in post from raw. Double check that it is set to 14-bit raw and not 12. – user10216038 Apr 16 at 2:26
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This is usually caused by the camera taking the scene as a whole and treating it as 18% gray. This is the way light meters (and camera meters) are calibrated to see the world. Scene mostly snow? 18% gray. Black cat in a coal mine? 18% gray. The camera doesn't know what you're taking a picture of, so it assumes that the scene is, on average, 18% gray and exposes accordingly. Your adjustment using the +-Ev feature is what we do to tell the camera what the real world looks like. Snow? +2Ev. Black cat? -2Ev. Here is a more detailed discussion of exposure compensation and how, why, and when to use it.

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    Interesting... I have a black dog and usually I wind up overexposing pictures of him too, otherwise I just see a black blob... :-D Also to add, that article was interesting and it linked to a second article on ETTR which mentioned that low contrast scenes tend to meter to underexposed (and vice versa) so that is something I will also keep in mind. – Michael Jan 16 at 5:33
  • Rather than thinking of cameras assuming the world is 18% gray, I think it's more useful to think in terms of assuming that the brightest and darkest parts of a scene will be within about 2.5 f-stops of the average intensity (18% gray is 2.5 f-stops below 100%), which will work out well with films that have about 5 f-stops of useful dynamic range. – supercat Jan 16 at 20:21
  • @supercat: The math is more complex than simply "18% ~ 100% / 2**2.5". There's a lot more than just 2.5 stops between middle gray and pure white. Films and digital sensors have had more than 10 stops of dynamic range for a long time now. – Eric Duminil Jan 18 at 12:41
  • @EricDuminil: The dark ends of film and digital don't have a hard saturation point, but do have a drop-off in quality. If one is shooting a dark scene, increasing exposure as much as possible without blowing highlights, motion blur, or unwanted focus blur, will allow one to achieve better results in later processing than would have been obtained if one simply shot dark. – supercat Jan 18 at 17:22
  • @supercat: Yes, but I don't see how it's related to your previous comment. It's simply wrong to say that middle gray is 2.5 stops below pure white. – Eric Duminil Jan 18 at 17:38
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Your camera's light meter measures brightness, but it can't tell if the brightness level it is measuring is a black cat in a coal mine or a white cat in a snowstorm.¹ It assumes everything you point your camera at is somewhere about halfway in between those extremes.

¹ Sure, the scene with the white cat will probably be brighter than the scene with the black cat (unless our blizzard is at midnight on a moonless night somewhere out in the boonies where there is no light pollution or maybe our coal mine is very brightly lit due to OSHA regulations), but the camera usually can't tell if that cat and its background is supposed to be black or white.

Unless you tell it otherwise, many cameras will try to expose whatever you point it at to that medium value.

Light meters have gotten a little more sophisticated in recent years, but you have to give them something to work with. When almost the entire field of view is more or less the same color and brightness, such as the sky in your examples, the added logic doesn't have much to go on. It's going to attempt to expose the sky as "medium brightness."

Some cameras are getting pretty good at guessing better with actual scenes, especially those with RGB+IR light meters which use all three primary colors plus near-infrared to meter the scene and compare it to a library in the firmware that will probably be able to tell the difference between a bright blue sky in the top of the frame and dark green forest in the lower part of the frame. The light meters in older and many entry level cameras are monochrome and can't meter in color, so they have to guess even more and often get tricky situations completely wrong.

Guidance from the photographer can go a long way, sometimes even when the photographer isn't necessarily very knowledgeable about the intricacies of exposure. One way a novice photographer can give the camera a hint is with scene modes. Most entry level cameras have a few or more scene modes.

Scene modes are a way for the less knowledgeable or less experienced photographer to tell the camera in what conditions the photo is being shot so that the camera can use the appropriate settings to maximize the chances of a successful photo.

One classic example: Snow or beach scene.

The more experienced photographer understands that a camera doesn't know if we are metering a black cat in a coal mine or a white cat in a blizzard. The more experienced photographer knows how to alter the camera's settings to make the scene look bright without totally overexposing the image or look dark without totally underexposing the image. The novice does not usually know they need to do this, much less how to do this.

Unless we tell the camera to do differently, the camera will try and make everything a medium brightness. So if the camera is set on full "Auto", a picture of a bright, sunny beach (or mostly empty sky) will underexpose a small, darker object on that beach (or in that sky) because the camera will expose the majority of the scene as medium bright!

"Snow/Beach" scene mode to the rescue!

We don't have to know how to adjust exposure for snow or bright sand at the beach, we just have to know to tell the camera we're taking a picture of a very bright scene by turning the mode dial to "Snow" and the programming in the camera will do the rest!

The same is true of the many other scene modes. It gives the less knowledgeable photographer a way to tell the camera what kind of scene they are shooting and the camera will attempt to pick the best combination of shutter duration, aperture, and ISO to use for that particular kind of scene. The photographer doesn't really need to know what the camera does to get there. They just need to be able to recognize the difference between a bright sunny day at the beach (Snow/Beach scene mode) and a night out on the town (Night portrait scene mode). They just need to be able to tell the camera they are shooting a running subject (Sports scene mode) or a static nature scene (Landscape scene mode). This allows the camera to emphasize what is most important for a particular type of shot. If conditions are less than ideal, the camera will use one of the other, less important factors for a particular type of photo to compromise and keep the most important thing as optimal as possible.

As a photographer begins to advance their knowledge and skill level, they learn how to use exposure compensation to tell the camera about the scene in front of them. Eventually they learn about different metering patterns and when each is most useful and how each affects what their camera's meter is telling them.

For example, rather than using positive exposure compensation with matrix/evaluative metering to brighten the sky, one could use spot metering to tell the camera to only meter a small portion of the field of view at the center of the scene. In the case of a black helicopter or airplane, for example, spot metering may actually require negative EC to prevent the black aircraft from being exposed as medium gray!

Notice, though, that due to the speed of the helo's motion, when your camera was at 1/250 seconds to expose more brightly the helicopter was blurrier than in the 1/1250 shots. In such a situation many photographers might consider intentionally underexposing by a bit, saving raw image files, and bumping up the exposure in raw conversion with relatively little penalty when compared to the disadvantages of trying to raise the brightness of an underexposed JPEG.

Ultimately, most experienced plane/bird in flight/airshow shooters wind up using manual exposure mode. One trick is to meter planes on the ground that are the same color and receiving the same light as the planes in the air. Another is to push the highlights in the sky to right at the edge of overexposure. Metering is followed by examining the histograms of test shots and adjusting if necessary. This works well on a clear day but may give mixed results if clouds are moving in and out of the sky while one is shooting.

There are a few manual exposure snobs that think shooting in any exposure mode other than manual exposure mode is unprofessional. I am not one of them. There is certainly a time and place when manual exposure is the best choice, but there are also other situation when other exposure modes may be better suited to getting the results one wants. Use what works for you in each situation that you find yourself shooting.

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    Spot metering when shooting planes require a very good aim. But a softer center-weighted option can help. – xenoid Jan 16 at 10:22
  • @xenoid It can really depend on the specific situation. What focal length/angles of view are involved with both the entire frame and the size of the specific camera's spot/partial metering circle? 1.5%, 2.5%, 5%, 9%, 12%? What size and at what distance are the aircraft? Etc. Sometimes center weighted average is not much better than evaluative/matrix at concentrating on the sky to the exclusion of the darker aircraft. – Michael C Jan 16 at 18:06
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    Great mention about the scene modes. I took the opportunity to reread about all the ones on my camera. "Beach/snow" is not something I would have thought about using for shooting at the sky, but I'll definitely try that! – Michael Jan 16 at 19:15
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    Yeah. Unfortunately, by the time a photographer realizes what a particular scene mode actually does to get the shots it gets and how that can be adapted to scenes other than the ones in the description, they no longer need the scene mode. They can dial the camera in themselves in PSAM/PTvAvM modes. – Michael C Jan 16 at 19:31
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    Does the D5xx0 series include spot metering that centers on the selected AF point, or is that only higher tier models? – Michael C Jan 16 at 21:10
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Other users here have given the technical answer to your question (which is correct too). Go to your camera settings and change metering option to spot metering. Thats it.

Go shoot!

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    Spot metering uses a spot of a defined size, and shooting a plane in the air will mean that even the spot is mostly sky with a plane shape in it. This might help, and is good for other uneven scenes, but probably won't expose properly. – JPhi1618 Jan 16 at 19:59
  • @JPhi1618 If the plane is not at least one third of the frame, the picture is usually not worth taking anyway. Unless you also want the smoke trails but then you expose for them, too. – xenoid Jan 16 at 21:04
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I would say it's all about exposure. Because how much lighter and darker the photos would be that relies upon shutter speed, aperture, and ISO. There must be limitations with all the values that allowed less light hence dark image.

Work again with your instructions manual and start by switching to S or A mode. Set your ISO to auto or something larger than 100, 400 should be enough. If the photos still turn out dark, your lightmeter might be defective.

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As mentioned in other answers, exposure compensation is an essential part of using any of the automatic modes (P,A,S). The good news is that is really not as difficult as it sounds.

Try not to think about light meters and how to compensate. Just remember that your camera want to make everything averagely bright. If you want your picture to be bright, set exposure compensation to +1 or 2, if you want your picture to look a bit darker, set it to -1 or 2. Very simple. I want my beach on a sunny day to look nice and bright, so I set it to +1.3 and I want my night shots to look much darker than a sunny beach, because the night is much darker than a beach, so I set exposure compensation to -2 for night shots.

This becomes second nature very quickly if you remember to consider exposure compensation for every shot in an automatic mode.

Also note that you do not need to look at the display for setting exposure compensation. Exposure is such an important setting, that every camera shows it in the viewfinder. Your camera has a big bar at the bottom showing the setting.

It is possible to use a different metering mode than evaluative, such as spot metering. That is not an alternative for using exposure compensation. The camera still goes for averagely bright, the only difference is that is only looking at a very specific spot now, instead of the whole picture. You will still need to turn down the exposure for your black dog, because it just isn't averagely bright.

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