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FORUMS Canon Cameras, Lenses & Accessories Canon EOS Digital Cameras 
Thread started 16 Feb 2015 (Monday) 13:06
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Question about Canon meter

 
jeljohns
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Feb 16, 2015 13:06 |  #1

I got an Expo disc and was reading about checking the accuracy of a meter using an Expodisc and the live view histogram. On 18% gray my histogram is in the center when my meter shows +1. I have also read this is very typical of Canon cameras. I tested this by going around the house and pointing at different subjects (light, dark). All pictures where I set my meter to +1 were properly exposed. So to get proper exposure my meter should always be at +1? Or just that all images should be 1 stop over what the meter says? So for instance if the meter reads -2/3 then I should actually be at +1/3?




  
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Sdiver2489
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Feb 16, 2015 14:47 |  #2

I think you are confused on the meter. The meter ALWAYS tries to expose the scene based on set criteria to the same overall average brightness. So there is no time that the meter will be -2/3 and need to by 1/3.

The only time the meter differs is when you feel it needs to shift based on the subject. If the subject is very dark then negative compensation might be necessary. If its very bright positive compensation might be necessary.

Therefore you should be able to leave your camera at +1 most of the time


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LV ­ Moose
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Feb 16, 2015 14:56 |  #3

I know nothing about Expodisk. I just know that on both my 5DIII and 40D I typically have EC set to +2/3 for proper exposure.


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Phototeacher
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Feb 16, 2015 15:43 |  #4

LV Moose wrote in post #17434652 (external link)
I know nothing about Expodisk. I just know that on both my 5DIII and 40D I typically have EC set to +2/3 for proper exposure.

My two 5DIIIs also require at least +.3 to +.6 exposure compensation.




  
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Feb 16, 2015 16:27 |  #5

Don't forget that the in-camera histogram is based on the jpeg processed image - change the picture settings/parameters and you can shift the histogram around...


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Wilt
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Feb 16, 2015 17:02 |  #6

jeljohns wrote in post #17434496 (external link)
I got an Expo disc and was reading about checking the accuracy of a meter using an Expodisc and the live view histogram.

Am having a hard time figuring out how you are using the Expo disc, and checking metering with it!
An Expodisc is put on the lens, then you stand at SUBJECT position and aim it at the theoretical camera position (where you will be taking the photograph from) and you get an 'incident' reading of the light falling upon the subject. Are you doing that?!


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jeljohns
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Feb 16, 2015 17:07 as a reply to  @ Wilt's post |  #7

Yes. The tutorial I read said to put the camera in live view with the histogram showing. Then with the Expodisc on you set your exposure until the histogram is in the center. When I did this I got a +1 reading (instead of zero).




  
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Wilt
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Post edited over 4 years ago by Wilt. (3 edits in all)
     
Feb 16, 2015 18:08 |  #8

It has long been a discussion point that you need to read a 12% reflective surface to get an exposure reading that results in the 'midtone' being in the center, rather than measuring an 18% metered target. The 15% target is about 1/2EV darker target than an 18% target, so if you measure 18% target it ends up to the left of midtone.


Do you have an 18% grey target, which you can measure with the camera's spotmeter, to compare that reading with the reading that you get with the Expodisk?


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Feb 16, 2015 19:30 |  #9

Heya,

I've yet to find a meter that exposed properly all the time.

I find most Canon meters, so far that I've personally used in 6+ cameras that I own(ed), I'm always at +2/3rds to +1 in terms of getting proper exposure. And for ETTR, I'm always around 1 & 1/3rd or more unless the highlights are popping off (which commonly are for me in Florida). I can at least dial it back down in post from RAW if I'm a bit too far to the right, which I'd rather be, than underexposed.

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jeljohns
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Feb 16, 2015 20:19 |  #10

I do have a gray card so I'll test that.

I guess my confusion is how to properly expose for an off meter. If I lnow my camera needs to be +1 stop to be properly exposed do I add that +1 to any meter reading?

For instance, I meter something dark. The camera essentially ends up overexposing it since it is trying to make gray...so do I still add +1 to that reading?




  
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Feb 16, 2015 20:53 |  #11

jeljohns wrote in post #17435121 (external link)
I do have a gray card so I'll test that.

I guess my confusion is how to properly expose for an off meter. If I lnow my camera needs to be +1 stop to be properly exposed do I add that +1 to any meter reading?

For instance, I meter something dark. The camera essentially ends up overexposing it since it is trying to make gray...so do I still add +1 to that reading?

Heya,

Depends on the metering method you're using. Spot & Evaluative, for example, will yield very different results depending on what your center point is facing (or the selected AF point depending on camera model).

If I'm shooting AV, I just dial in an extra +1 or +1 & 1/3rd EC on the meter. To force that.
If I'm in Manual, I just look at my histogram, check the meter, and push it to the right until it looks right on the histogram, or, if I see the meter at 0, I push it to the right until it's closer to +1.

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Post edited over 4 years ago by Wilt. (3 edits in all)
     
Feb 16, 2015 21:02 as a reply to  @ jeljohns's post |  #12

The 18% grey card should end up at the center of the histogram if you read the 18% card with the camera's spotmeter and add 1/3EV to the suggested exposure.

If you read a 12% grey card, the 18% grey card should end up at the center of the histogram if you read the 12% card with the camera's spotmeter and expose at the suggested (unmodified) exposure.

IF you have to increase exposure more than 1. the suggested exposure (12% card) or 2. by adding 1/2EV to the suggested exposure (reading the 18% card) you meter is off.

Assuming, for example, that you find your meter is off by 0.66EV, you add 0.66EV when metering the 18% grey card. But if the surface you measure is 0.66EV brighter (light grey) than 18% grey card, you have to add 1.13EV (0.5EV correction for meter error + 0.66EV for brighter target surface used for metering)


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sandpiper
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Feb 16, 2015 21:11 |  #13

jeljohns wrote in post #17435121 (external link)
For instance, I meter something dark. The camera essentially ends up overexposing it since it is trying to make gray...so do I still add +1 to that reading?

No, you use your judgement to decide how much you need to correct for the dark tone and adjust from that, taking the fact that you like to shoot at +1 for a "typical" scene. So, if you have a black subject filling a large part of the frame, you would expect to have to use a setting about one and a half stops below typical to keep it black. In that case you would set it about half a stop under.

Similarly if shooting a snow scene, where you want to keep the snow white and the meter wants it grey, you would normally expose by maybe one and a half stops above typical, so allowing for your normal +1 that would mean setting two and a half stops above the meter reading.

I imagine my 5DIII is also around the same metering as others here, I am more often shooting at +ve EC (or equivalent in manual) but I don't simply set +1EC all the time. On a shoot it can vary between -2 and +3 depending on what I am shooting at the time, I suppose I am typically between 0 and +1 for the majority though. You just have to use the meter (and histogram) to guide you and your judgement to know when, and by how much, to modify the exposure. I shot an event a while ago when the whole event was shot at between -1 and -2 because they held it at lunchtime, in direct sunlight, with some participants wearing white outfits. One person I know left his camera at +1 "because it always needs to be +1 on Canons" and said I would get crap results. However, whilst I did have to bring up the exposures in post, my shots were fine and I had lots of detail in the whites. His, on the other hand, were positively glowing, they had huge white holes in the images with heads and hands sticking out of the blown out clothing.

So, yes, take the +1 into account, but also take into account what you are shooting and the lighting (+1 may still work with white clothing on a dull day) and if in doubt, take a test shot and see how the histogram looks. Remember if shooting raw that you are best with a "faithful" or "neutral" picture style as they give a more accurate histogram. Turning on the "blinkies" can also help as you can see where the image is blowing out - it may be somewhere that doesn't matter.




  
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jeljohns
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Feb 16, 2015 21:26 |  #14

Thanks Sand Piper. I think I get it now.




  
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GeoKras1989
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Feb 17, 2015 04:14 |  #15
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EC is available for a reason.


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Question about Canon meter
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