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11-04-2014, 07:57 AM   #1
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Exposure compensation

Hi all,

I have a question regarding exposure compensation. I have never used this on regular basis and I do not understand what is going on.

If I am using manual Mode the EV changes by itself.
If I am using the TAv Mode and take a picture with EV +5 it will be the same as one with EV -5 (leaving all the other setting the same)

What do I have to do if I want to take let's say a darker picture with some give settings (aperture, shutter speed and ISO). Wouldn't a -5EV suffice?

I know there is nothing wrong with the camera and it is me so any explanation would be appreciated. Yes, I am a noob.

s

11-04-2014, 08:17 AM   #2
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In Manual mode it shows you if your will be over or under exposing the image. Manual does not have compensation. TAv is like manual mode but with autoiso so depending on how you have set your autoiso limits, shutter speed and aperture you may come to a setting where you hit a ISO limit and the ISO number starts blinking. If so the exposure will be the same
11-04-2014, 08:19 AM   #3
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The difference between -5 and +5 EV should be night and day.
In Manual mode, exposure compensation just changes where Zero is on the meter.
In TAv mode, the only thing the camera can adjust is ISO. If you compensate -5 in daylight and the camera can't adjust ISO any lower than 100, you won't see much difference.
11-04-2014, 08:24 AM   #4
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Ok, makes sense. Thanks Tjompen1968 and AquaDome. I was forcing the ISO to be the same (100-125) to see if EV would do anything in TAv but if it works as in Manual that explains the results.

So going back to the other question, I cannot leave all settings the same and play only with EV to make an image darker/brighter?

11-04-2014, 08:31 AM   #5
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Bear in mind that you can fiddle with exposure compensation in manual mode, too. The exposure itself won't change (after all, it's only the shutter speed, aperture and ISO that determine the exposure, so if you don't touch them, nothing will change), but the exposure indicator will take the compensation value into account. So, if you don't set any compensation, the indicator will show you how much over/under you are in relation to the "correct" exposure (what the camera thinks is correct). If, for example, you set a +2EV compensation, the indicator will show how far from that +2EV value you are, with your given settings. (in other words, if you set a +2EV compensation and you change the settings so that the meter is in the middle, your picture will be overexposed by 2 stops).
Also, if you're in manual mode, if you have an external flash mounted on camera in P-TTL mode, and you set the exposure compensation, that compensation will influence the flash output. So the ambient light exposure will remain the same, but the flash output will be stronger/weaker depending on the compensation.
Might sound a bit confusing at first, but give it a try and you'll get it.
And it may not be an answer to your questions Just something to be aware of.
11-04-2014, 08:32 AM   #6
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QuoteOriginally posted by sergysergy Quote
So going back to the other question, I cannot leave all settings the same and play only with EV to make an image darker/brighter?
No. EV Compensation needs to be able to adjust something up or down to add or subtract the light.
11-04-2014, 08:53 AM   #7
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Put it in P mode to see how the exposure changes with exposure compensation.


If you want to make the jpeg image darker or brighter without altering the exposure, try the high/low key setting in the custom image screen.


Regards,
--Anders.
11-04-2014, 09:07 AM   #8
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QuoteOriginally posted by sergysergy Quote
Ok, makes sense. Thanks Tjompen1968 and AquaDome. I was forcing the ISO to be the same (100-125) to see if EV would do anything in TAv but if it works as in Manual that explains the results.

So going back to the other question, I cannot leave all settings the same and play only with EV to make an image darker/brighter?
In Tv, Av, Sv, TAv and P the EV-comp will make the image lighter or darker IF there is room for it, i.e if in Av it will change the shutter speed but if you hit 1/8000 or 30s it will start blinking telling you that you have hit a limit. Then you have to adjust your aperture to give room.

Same for Tv but then it is the aperture that hits the limit and starts blinking.

Easiest mode is P or Sv because it has two values to play with. When one hits a limit is will edit the other. (If P + AutoISO it will edit the ISO first)

Using TAv mode you need to give the camera room to work, i.e setting the ISO-limits to 100-125 it will have no room to adjust. Only by ISO25 which is pretty much no visible change... I use 100-8000.

11-04-2014, 09:30 AM   #9
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QuoteOriginally posted by sergysergy Quote
So going back to the other question, I cannot leave all settings the same and play only with EV to make an image darker/brighter?
Nope. There is only one way to make an image darker or brighter: change the exposure.

And there are three ways of changing the exposure, of course:
- change the aperture
- change the shutter speed
- change the ISO value

If you don't let the camera change either of those three it can't possibly make an image lighter or darker. (Well, unless you let it add flash...)

The point of the EV comp is to tell the camera to pick an exposure that is different from what it would otherwise have picked. Trying to take a picture of a bird flying over a bright sky will typically make the camera expose for the sky, not the bird. So then you can dial in +2 EV to tell the camera to brighten up the image, even if it means turning the sky bright white.
11-04-2014, 09:49 AM   #10
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QuoteOriginally posted by savoche Quote
Nope. There is only one way to make an image darker or brighter: change the exposure.
What he said!

The difference between metering and exposure is a common source of confusion. The meter measures light. That is all it does. The various exposure modes in conjunction with EV comp* reflect different ways of leveraging the meter to control the exposure. In M mode, you have complete control of all three exposure variables (aperture, shutter, and ISO) and the meter serves mostly to advise.


Steve

* EV compensation merely applies an additive bias to the meter reading. At +2 EV comp, a meter reading of EV 8 is treated as EV 6 (2 stops less light requiring 2 stops more exposure). It does not make the meter any more or less sensitive or change the sensor sensitivity or anything else. All that changes is a number.

Last edited by stevebrot; 11-04-2014 at 10:01 AM.
11-04-2014, 10:42 AM   #11
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QuoteOriginally posted by sergysergy Quote
What do I have to do if I want to take let's say a darker picture with some give settings (aperture, shutter speed and ISO). Wouldn't a -5EV suffice?
So, yes, as others have said, you cannot. Aperture controls the amount of light hitting the film plane (sensor), shutter speed controls how long the light is hitting the sensor, and the ISO is the sensitivity of the sensor to light. Apart from using photoshop or other editing programs after you take a photo, these are the only ways to achieve brighter or darker photos. It is a balancing act, to get a shutter speed fast enough for sharp photos (no hand-shake blur, no subject movement blur), and aperture for a good DoF (small f-number means shallow DoF with lots of blur, while high f-number means wide Depth of Field/focus area). A high ISO number can introduce digital noise, so it is good to keep it as low as possible, but going up to ISO 1600, 3200 should be no problem with modern digital cameras.

EV is only exposure value. Each scene, room in front of you, has a certain amount of light. This is measured by EV. Digital cameras don't tell you what EV is out there, they just compare it to EV=0, which should be the "perfect" exposure according to the camera. When you choose EV -1, it only means the camera will select a higher aperture, lower ISO, or faster shutter speed to make the photo darker by 1 EV. This is why in M mode, you cannot choose EV, the camera just shows you what EV your current settings give you.
11-04-2014, 10:45 AM - 1 Like   #12
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QuoteOriginally posted by savoche Quote
Nope. There is only one way to make an image darker or brighter: change the exposure.

And there are three ways of changing the exposure, of course:
- change the aperture
- change the shutter speed
- change the ISO value
Ok, this is what I have always done with all my cameras. I just thought I was missing something something with the EV. I guess I will leave it untouched then. Thanks so much for all the explanations for dummies!
11-04-2014, 02:44 PM   #13
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Basically when in TAV mode you are telling the camera, Hey I want this Aperture and that Shutter Speed, you do what you have to do to make it happen. So the ISO gets adjusted to oblige. What I have found, at least on my K3, is that if I forget all this and dial in an EV adjustment when in TAV mode all I need do is switch to P mode and the desired EV is already there waiting for me!

Jeff
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