I keep reading about EV and I'm not sure I understand it. Can someone recommend a good read that would explain it? I read about exposure compensation +/- 1/3, 1/2 stops etc. How is this done? Does it mean changing aperature by one setting or shifting to a faster or slower shutter speed? Any explanation would be greatly appreciated.

Mike

"Faith is the daring of the soul to go farther than it can see"
-William Newton Clark

Visit my Nikonians gallery.

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LAST EDITED ON Jul-21-01 AT 03:23 AM (GMT)

Mbowker,
EV is exposure value. This refers to the amount of light "seen" by your camera's meter. Most cameras can meter from around 0-20EV, give or take. Low candlelight is around EV 4 or so, while bright sunlight is around 16-20 depending on brightness. Any book on photo technique can explain this more thoroughly. I personally like "The Basic Book of Photography" by Tom & Michelle Grimm. Easy to understand. EV is totally separate from exposure compensation. EV is really only relevant as pertains to whether or not your camera can meter a given scene. If the scene is too dark or too bright, your camera's meter won't function.
Compensation involves knowing your camera and whether or not your given exposure mode will meter correctly based on contrast, etc. e.g., in a backlit scene such as with bright sand or snow as a background, you will often need to overexpose based on your camera's meter reading or else the subject will appear underexposed. The reverse is true of a bright subject on a dark background. Your camera, depending on exposure mode, "reads" the entire scene. If your main subject is much different than the overall scene, compensation may be helpful or necessary.
+ & - 1/3 or 1/2 stop refers to how much compensation is needed. e.g., + 1 or 1.5 stops is the norm for a strongly backlit scene where the subject is much darker than the background. Compensation can be done either with shutter speed or aperture as they both impact the overall exposure. Which one you choose depends on the situation. If shooting moving subjects, it is usual to change the aperture to maintain a shutter speed that will stop the action. Shhoting static subjects is easier. Changing aperture will affect depth of field.

Hope this helps, but it sounds like you could relly use a good photo technique book.

Good Luck,
Jeff Johnson

EV can be explained as the range of combinations of shutter speeds and aperture values that correspond to the same final exposure. If you number these ranges, you have EV (Exposure Values).
An EV of zero will correspond to the exposure time of one second and the aperture of F/1.0. EV 1 is either a half second and F/1.0 or one-second and F/1.4 and so on.
If you combine the exposure value with a specific film speed, EV numbers can be used to indicate the brightness of an object. Without the addition of film speed into the equation, exposure values indicate nothing more than camera settings.
Most camera manufacturers use EV to indicate the sensitivity of their AF and metering systems. The Nikon F5 has an AF detection range of EV –1 to EV +19 and a metering range of EV 0 to EV 20 (at a rated 100 ISO). Now, if you mounted a lens with an aperture of F/1.4 to the camera the metering system would be accurate between EV 0 to EV20. However, if you mount a lens with an aperture of F/2.8 the meter now senses three stops less light than with the F/1.4 lens so the metering system is now accurate between EV 3 to EV 23. (All EV ranges are rated at 100 ISO).
It is quite easy to set up a chart in excel to set up EV ranges. However, to try to explain it here could take some time. If you would like I have an EV chart in an excel file that I would be happy to email to you.

Doug

--Take only photographs, leave nothing but footprints--

NC, second week of October, 2001...

"Take only photographs, leave only footprints"

  

I appreciate the offer Doug, but unfortunately, I don't have excel. Do you think it would work in the MSWorks spreadsheet?

I think I'm beginning to understand about exposure compensation but I'm not sure yet. If I want to take a picture and my camera meter says 1/250 at f5.6 and it has a dark background and say...I want to lighten the background...I open the aperture to f2.8. I just made an exposure compensation, right? Now, did I just adjust it 1/3, 1/2 or what. Is each step on the aperture ring of my lens a 1/3 stop? How much of a "stop" is each change of shutter speed or does it matter depending on the ratio in the shutter speed steps? (i.e from 1/125 to 1/250 as opposed to 1/250 to 1/350 etc.)

Mike

"Faith is the daring of the soul to go farther than it can see"
-William Newton Clark

Visit my Nikonians gallery.

Visit my Nikonians gallery.

I appreciate the offer Doug, but unfortunately, I don't have excel. Do you think it would work in the MSWorks spreadsheet?
Probably not…

I think I'm beginning to understand about exposure compensation but I'm not sure yet. If I want to take a picture and my camera meter says 1/250 at f5.6 and it has a dark background and say...I want to lighten the background...I open the aperture to f2.8. I just made an exposure compensation, right?
If you are in aperture priority and you open the aperture to F/2.8 from F/5.6, the computer will lengthen the shutter speed to maintain the same exposure, and the shutter speed will move two-stops to 1/60. This affectively gives you the exact same exposure as you had before you changed the aperture. However, if you use the compensation dial on your camera, the aperture will stay at F/5.6 since this is what you manually set it to, and the computer will vary the shutter speed by the exposure compensation you requested.
For example if you are in aperture priority mode, and you set the aperture to F/5.6, and the shutter is showing 1/250, and you compensate one stop over and one stop under exposure, the camera will take three photos. All photos will be at F/5.6 however, the over exposed frame will be at 1/125 (slower shutter speed…more light), the underexposed frame will be at 1/500 (faster shutter speed…less light) and the normal exposed frame is at 1/250.
Of course, you can shoot in full manual mode and adjust both the aperture and shutter speed to what ever you consider appropriate.

Now, did I just adjust it 1/3, 1/2 or what. Is each step on the aperture ring of my lens a 1/3 stop? How much of a "stop" is each change of shutter speed or does it matter depending on the ratio in the shutter speed steps? (i.e from 1/125 to 1/250 as opposed to 1/250 to 1/350 etc.)
The standard sequence of F-stops in one-stop increments is:
F/1.0 F/1.4 F/2.0 F/2.8 F/4 F/5.6 F/8 F/11 F/16 F/22 F/32 F/45 F/64

For half-stop increments: F/1, F/1.2, F/1.4, F/1.8, F/2, F/2.5, F/2.8, F/3.5, F/4, F/4.5, F/5.6, F/6.7, F/8, F/9.5, F/11, F/13, F/16, F/19, F/22, and so on…

The standard sequence for shutter speeds is:
8, 4, 2, 1, ½, ¼, 1/8, 1/15, 1/30, 1/60, 1/125, 1/250, 1/500, 1/1000, 1/2000, and so on…

Hope this info helps.

Doug

--Take only photographs, leave nothing but footprints--

NC, second week of October, 2001...

"Take only photographs, leave only footprints"