Posted: 8/9/2007 5:45:53 PM EDT
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I recently picked up a 70-200mm lens for my camera. I normally shoot aperture priority and with this lens my pics are under exposed using the same f-stop as my 18-55 mm. I know this is something simple and I'll kick my ass but being on the upward slope of my learning curve it's got me stumped. |
Not so fast there. That's what you should be shooting for IF that's what you want.  See, exposure compensation (the correct designation imho is EV, not EC) is a good thing if you know how to use it. Sometimes you need to compensate for the exposure the camera selects. For example, let's say you're shooting grandma and the sun is to her back so she doesn't have to squint. That's all well and good since she'll have a nice, happy expression. You set your nifty dial to Av (aperture priority) and dial it in to about f/4 to give a moderate depth of field. The camera meters the scene, sets the shutter speed and you snap the pic. Damnit! Grandma's face is so dark you can barely see her.  wth? Stupid camera's a POS. Well, not really...What happened is when the camera metered the scene to make its shutter selection, the bright light from the sun backlighting grandma confused it. It was too bright and the camera thought, "Oh dear, I really need to set a fast shutter speed to ensure the picture isn't overexposed." By setting a fast shutter speed it didn't allow enough time for grandma's face to be properly exposed. A simple solution to this is to use +EV. You need to experiment with how much is enough, but you might try adding one stop (+1EV). I bet the next pic you take will let you see grandma's face now. Of course the same concept works in reverse. Shooting youth sports (team/individual) I often use +EV to set a proper exposure w/o having to pop the flash. Hope that made sense. |
In Aperature Priority mode, they camera determines the shutter speed, based upon the ISO value and aperature you chose. When you turn the dial, you are changing your Exposure Compensation which afects your shutter speed as a result. You aren't adjusting the shutter speed, you are telling the camera how much, or how little, light should be allowed in based on it's "reading". Since you have manually set the ISO and Aperature, the only thing the camera can change is the shutter speed. If you were in Shutter Priority mode, turning that dial would set the EC, and the camera would be forced to open or stop down the aperature to compensate from it's base reading. If you are in manual mode, you set the aperature, shutter and ISO. The needle in the camera will tell you if it believes it's internal meter agrees with your settings. To do your testing, set the EC to 0. Shoot a scene with both lenses at the same ISO and Aperature, and distance. |
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Your pic turned out fine. By exposoure, I mean Your camera catches reflected light to make the image. Look at the shadow. The light is coming from the man's front. How much light is going to hit directly on his back, to reflect to the camera? Not a whole lot. If you had metered for the light reflecting off the man's back, you would have ended up with overexposing the sky and the landscape as well. The sky would have been blown out, and the colors in the landscape would be washed out. In these types of situations, you need some sort of fill. Either fill flash, or using a reflector to add light into the dark areas. |
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That picture looks exactly as it ought to. The sky and the grass are exposed well. What to do about that dark figure? 1) Expose for the figure, not the scenery. You can do this any of a few ways... a. Use a spot meter and use the subject to lock the exposure so that when you recompose, the figure is properly exposed. b. Use a spot meter, and in manual mode, set the aperature/shutter/ISO to give you the proper exposure while you are pointing at the subject. Recompose and shoot. c. Use your regular matrix meter, and dial in an EV value of +1.0 to +2.0 trying various values in between as well. This will bump the camera's exposure up that number of stops from it's automatic setting. 2) Use a fill flash!  3) Take a series of bracketing photos from a tripod, using shutter speeds from -3 EV to +3 EV, and then choose the two or three with the best earth and sky and subject, and layer them in Photoshop. Layer them from light to dark, with light being on the bottom, and then erase away the under exposed areas of the dark exposure, revealing the properly exposed portion of the lower layer. This takes time, but is the only way to stretch the dynamic range of a digital photo to match what the human eye can see. |
Options a and b would overexpose the scene, as they are correctly exposed now. If the shutter is left open longer to correctly expose for the mans back, the rest of the scene will be overexposed. Option C is a good way to go, as well is using a reflector. Option D will also work, I'd suggest learning how to capture the image in the camera correctly the first time, rather than adjusting for it in photoshop. Learning how the camera and meter work, would make you a better photographer and would take a LOT less effort than trying to fix it in post. |
+1 |
+1 Another tip: When shooting on big flat surfaces (fields, the beach...) kneel or sit down. That way, you can raise the horizon line much higher in the picture, without having to avoid the look of shooting at the ground. Your pic doesn't suffer from this, but many I see do. On my most recent vacation, I forced myself to do this by using a monopod, and keeping it most of the way collapsed for some scenes. shooter |
Thanks for the tips guys. I've used photoshop to fix what I thought were under exposed pics before. The only flash I have right now is the one one the camera. Would it work as a fill flash at that distance? |
thanks again for the help. I'll give it a try asap. It's easier to find excuses to shoot pics then it is targets.. |