# Do You Center The Meter?



## smoke665 (May 10, 2017)

There was a comment in another thread that led me to do a little experimenting with my camera. I discovered that when using camera spot meter, if I center the meter, I'm still about 1 to 1-1/2 stops short of a full exposure when viewing the histogram. 

Do others experience this? Do you compensate by overexposing according to the meter, or do you adjust it post? Theory behind your choice?


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## The_Traveler (May 10, 2017)

Everything depends on the nature of the 'spot' you are metering. Use exposure compensation to adjust the exposure to put that spot where you want on the histogram.


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## smoke665 (May 10, 2017)

The_Traveler said:


> Everything depends on the nature of the 'spot' you are metering. Use exposure compensation to adjust the exposure to put that spot where you want on the histogram.



I agree, but the other thread that started me checking, has me wondering now if the camera manufacturers are adjusting the meter readings to a properly exposed JPEG and not a full sensor.


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## fmw (May 10, 2017)

The Traveler has it right.  Meters are designed to render a 15% gray subject at proper exposure.  Spot meters are normally used to measure dynamic range by comparing readings between shadow and highlight.  If you put the spot on a shadow, the meter will recommend an overexposure.  If you have enough experience to recognize what would be a 15% gray area in your subject, then placing the spot there will expose that area and probably the entire subject correctly. 

In other words using a spot meter requires practice.  Spend some time comparing various results with the spot meter to the matrix meter.  In time, it will all come together.


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## smoke665 (May 10, 2017)

fmw said:


> a 15% gray subject at proper exposure



True, but is that a proper exposure for a JPEG per the camera manufacturer internal software - meaning it's hedging on a full ETTR?


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## KmH (May 10, 2017)

The file type does not matter.

Plus, being a mass produced product, each camera's meter will perform a little differently based on how accurately the meter was calibrated on the assembly line.

Note too that Nikon DSLR cameras have color -aware metering.


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## Gary A. (May 10, 2017)

Meters, all meters will calibrate to a medium gray, a gray card, (12%-18% gray).  (Internal software adjustments notwithstanding.)

If you sample a black wall, center the needle, the wall will come out medium gray.  If you sample a white wall, center the needle, the wall will come out gray.  If you sample wall that is similar in density to a gray card, your wall will be perfectly captured.

Using Spot, you need to understand how the meter reads.  If you Spot a white person's skin, you have to open up a stop to a stop and a half to compensate for medium gray, (as white skin is lighter than medium gray), and to attain a 'proper exposure'.  If metering off a person of color's skin, you have to underexposure to attain a proper exposure.

When using Spot, you really have to look hard at what is in the 'spot' then adjust accordingly, using medium gray as a reference, (either overexpose for a subject lighter than medium gray or underexpose for a subject darker than medium gray).

Spot is great for landscapes and architecture and studio work when you have time to sample different areas and find a happy exposure that doesn't clip highlights or shadows (if that is what you desire). Spot is great in a fluid/changing environment when the subject is vitally important and the other elements in the image are secondary (photojournalism).

When I use Spot, (some 90% of the time), usually I'm in a fluid environment action situation. If I am waiting for the subject I'll meter off a known substance, like grass and close it down a stop or two, a street lamp, road top, et cetera and adjust accordingly, then when the subject arrives I'm in the ballpark ... and I can shoot confidently with my original setup exposure or if I have time I can sample the subject and tweak the settings to fine tune the exposure. If the subject is a person, I'll look for something medium gray on the subject and compare that reading to reading a skin tone plus a over/under adjustment for skin coloration.

My techniques can be used with any metering mode, but with Spot you know exactly the zone/density of the sampling.

Meters are guides and are not to be taken literally.


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## KmH (May 10, 2017)

Gary A. said:


> Meters are guides and are not to be taken literally.


Yep.

And is why many photographers use a hand held meter so they can not only meter reflected light but also incident light and strobed light (flash).


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## Gary A. (May 10, 2017)

smoke665 said:


> The_Traveler said:
> 
> 
> > Everything depends on the nature of the 'spot' you are metering. Use exposure compensation to adjust the exposure to put that spot where you want on the histogram.
> ...


" ... not a full sensor ..."?
I could be wrong, but if I recall correctly, there may be a slight exposure difference between RAW and JPEG.


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## Gary A. (May 10, 2017)

KmH said:


> Gary A. said:
> 
> 
> > Meters are guides and are not to be taken literally.
> ...


Lately, with my EVF cameras, I've been getting lazy and adjusting the setting per the EVF.


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## Braineack (May 10, 2017)

smoke665 said:


> I discovered that when using camera spot meter, if I center the meter, I'm still about 1 to 1-1/2 stops short of a full exposure when viewing the histogram.



the spot meter, as described, meters a small area...
the histogram, displays the content of the entire capture...

how are you using a histogram to tell you you're under exposed?

if you spot meter on the only light source in a scene, i'd expect a HEAVY left-weighted histrogram -- doesn't mean you're underexposed, just that there's a lot of black in the capture, since you exposure for the light.


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## fmw (May 10, 2017)

smoke665 said:


> fmw said:
> 
> 
> > a 15% gray subject at proper exposure
> ...



It isn't hard find out.


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## smoke665 (May 10, 2017)

Gary A. said:


> Meters, all meters will calibrate to a medium gray, a gray card, (18%-22% gray). (Internal software adjustments notwithstanding.)



You'd think but I'm beginning to wonder. Centering the meter gives a useable exposure for both JPEG and Raw, it just seems like it consistently stops short of a full sensor exposure.


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## table1349 (May 10, 2017)

Most DSLRs have meters calibrated t0 approximately 12% gray.  That is the reason for more and more gray test media being made of 12% gray material.  The differences between 12% and 18% are not much.


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## Braineack (May 10, 2017)

smoke665 said:


> You'd think but I'm beginning to wonder. Centering the meter gives a useable exposure for both JPEG and Raw, it just seems like it consistently stops short of a full sensor exposure.



but where are you aiming the center spot at?   that matters -- you're only exposing to that spot...


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## table1349 (May 10, 2017)

Centering the meter is not always the exposure you want.  I know how close to 1/3 stop each of the spots on my meter are and can adjust for the scene as necessary from the meter as I want it.  There are times to over expose a bit and there are times to under expose a bit.  Perhaps this is just a hold over habit from my film days.


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## Gary A. (May 10, 2017)

smoke665 said:


> Gary A. said:
> 
> 
> > Meters, all meters will calibrate to a medium gray, a gray card, (18%-22% gray). (Internal software adjustments notwithstanding.)
> ...


My ignorance, but what do you mean by "... a full sensor exposure"?  The Spot only samples the 'spot', (usually somewhere between 1 to 10 degree spot), and provides the exposure setting based upon medium gray for that individual spot.


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## smoke665 (May 10, 2017)

Gary A. said:


> a full sensor exposure"



As much data as possible without blowing the highlights. I may not have stated it right in the OP, I know how to get a proper exposure, how to use the in camera meter and my hand held. I routinely use a combination of judgement,  average of spot readings, and watching the histogram, to determine the "correct exposure ".  However, it's a known fact that different manufacturers apply certain "proprietary adjustments" to both the Raw file and a processed JPEG, so is it possible that they also calibrate the meter to give a proper exposure per "their standards" for a JPEG processed by their internal software, regardless of if you saving  Raw or JPEG? 

Here's an example of something I was playing with the other day. I had the camera set to Raw+ (save both Raw and JPEG to card). I maximized the exposure per the histogram (which by the meter was not quite a full stop right of center). The first image is the histogram from the Raw File. 



 
The second image below is the histogram from the JPEG created from the same exposure at the same time


 

The Raw file had maximum data and showed no sign of blown highlights when opened post but the JPEG looked over exposed. Had I centered the meter, the JPEG would have been properly exposed, and the Raw would have needed a bump in post. 

Am I missing something?


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## Overread (May 10, 2017)

Overexposure is when the line hits the far right hand side rather than when it peeks through the top of the graph; just as full underexposure is when it hits the far left hand side rather than doesn't appear at all. 

JPEGs always have some editing applied because they are essentially adjusted RAWs - even on faithful/neutral settings some changes have to be made. It's also important to realise that in the camera the RAW should have the same data because the RAW uses an embedded JPEG edited to the same standards as the settings you've got set for JPEG editing.

When you take the photo out of the camera and use software for the RAW the software has to pick a starting point for all its settings to display the RAW as an image. As a result different software options will display the same RAW slightly differently. It's still the same data underneath; just different default starting points.


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## smoke665 (May 10, 2017)

Overread said:


> Overexposure is when the line hits the far right hand side rather than when it peeks through the top of the graph;



Agreed, this represents the point where I had pulled back as more exposure sent it up the right side, but again the question I'm asking.

"Is it possible that camera manufacturers calibrate the in camera meter to their proprietary standards for a JPEG, or is it a true reading based on gray scale?"


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## fmw (May 10, 2017)

smoke665 said:


> fmw said:
> 
> 
> > a 15% gray subject at proper exposure
> ...



Easy enough to find out.


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## Ysarex (May 10, 2017)

smoke665 said:


> Gary A. said:
> 
> 
> > a full sensor exposure"
> ...



A little fly in the ointment -- that's not a raw file histogram you're looking at there. That's the histogram of an RGB file processed from the raw file and already substantially manipulated by the processing software. If you exam the actual raw histogram I suspect you'll find the discrepancy you've noted is in fact greater than this would indicate.

Joe


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## Ysarex (May 10, 2017)

smoke665 said:


> Overread said:
> 
> 
> > Overexposure is when the line hits the far right hand side rather than when it peeks through the top of the graph;
> ...



The camera manufacturers calibrate their camera meters to a standard brightness (gray scale if you like) for the ISO value they've assigned to the camera. Now think of that and your original question in light of this simple fact. The sensors in your and all of our cameras do not have rated or assigned ISO values.

Joe


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## smoke665 (May 10, 2017)

Ysarex said:


> That's the histogram of an RGB file processed from the raw file and already substantially manipulated by the processing software



I forget a lot of things, but most of what you've told me I remember, this is one of those things I remember.



Ysarex said:


> Now think of that and your original question in light of this simple fact. The sensors in your and all of our cameras do not have rated or assigned ISO values.



So if I extrapolate this statement, combined with other information I know then the  answer to my question is yes? Camera manufacturers can/do adjust the in camera meter to a proprietary setting, other than adhering to a standardized gray scale reading.


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## Gary A. (May 10, 2017)

Yes.  Sorta like film.  Different color films have different characteristics even though they may share similar ASA.  Difference cameras will put an individual manufacturer's fingerprint on your capture.


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## Ysarex (May 10, 2017)

smoke665 said:


> Ysarex said:
> 
> 
> > That's the histogram of an RGB file processed from the raw file and already substantially manipulated by the processing software
> ...



Not exactly. They calibrate the meter to achieve a standard brightness level in the output JPEG. If you look at the ISO standard for a digital camera, the ISO value is set based on the output of the camera's JPEG processing software. That's why I mentioned that the sensors don't in fact have assigned ISO values.

So the meter is well calibrated to do its job and the brightness level standard (good exposure) is shared between the different manufacturers. The point where they put a spin on it all is in the processing software that creates the JPEG. Here they make a conservative choice between JPEG exposure versus raw file exposure and that's the discrepancy you're seeing. They design the JPEG processing software to render a standard brightness JPEG from a conservatively (under) exposed raw file and the meter is adjusted to that software's JPEG output. So the calibration for the meter isn't what's proprietary here so much as the processing software that creates the JPEG.

Joe


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## smoke665 (May 10, 2017)

Ysarex said:


> The point where they put a spin on it all is in the processing software that creates the JPEG



True to a point, though we've had the conversation before as to what they actually apply to a Raw file. IE pretty much accepted that all manufacturers apply  some noise reduction regardless of the menu settings.


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## Ysarex (May 10, 2017)

smoke665 said:


> Ysarex said:
> 
> 
> > The point where they put a spin on it all is in the processing software that creates the JPEG
> ...



Oh sure -- they do a whole basket full of stuff as they convert and process the raw file into a JPEG, including stuff they keep locked in a safe. The raw file is demosaiced, white balanced, tone curve applied with any user supplied additions like highlight/shadow settings, distortion adjusted, CA removed, noise filtered, and at least sharpened. All of that is spin and all of that is the end product they're selling. They sell a camera that creates a finished photo when you click the shutter.

If you save a raw file as well you'll find that they designed all of the above to make a good JPEG from a raw file that's conservatively exposed.

Joe

P.S. The free software RawTherapee includes an option to display a raw file histogram.


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## DanOstergren (May 13, 2017)

I use it as a starting guide, then adjust the exposure according to how I want it the look.


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## smoke665 (May 15, 2017)

DanOstergren said:


> I use it as a starting guide, then adjust the exposure according to how I want it the look.



Agree, pretty much SOP for most. My post was more to the question of understanding how camera manufacturer's might "alter" the meter reading. To find a common starting point to adjust from.


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## Bebulamar (May 15, 2017)

When I use the spot meter my exposure can be all over the place because it depends on where I point the spot to.


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## pez (May 20, 2017)

I use back button spot focus and let the camera do average metering, shifting to a different area of the frame briefly and holding the exposure button if there is back lighting, etc. Sensors are so good now that you can pull out a couple of stops one way or the other in post if you have to...


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## table1349 (May 24, 2017)

How to Understand Your Camera's Light Meter and Get the Exposure You Want


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