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Wed Jul 24, 2013, 04:26 PM

Photography 101 ... Exposure and Metering Quirks

As the newbie as registered DUer, (long, long time lurker) I thought that since the photography group is my favorite place to post and read and visit after I scan the latest and greatest threads, I will periodically post little lessons for those interested in learning more about photography.

Most of the info I will post can most likely be found in that little manual that came with your camera ... but who reads that stuff, eh!? It can also be found all over the interwebs. But these little lessons will be coming at 'cha straight from a DUer. How great is that!?

I start with exposure and metering quirks ... one of my favorite subjects. The reason I am beginning with this is because cameras are stupid. Armed with a bit of knowledge, one can compensate for the camera's lack of reasoning and command it to do your bidding.

Let me begin. Ahem (clearing throat)

A camera on automatic setting wants to make every picture you take a perfect exposure. And this is great if what you are taking a picture of is of "average" exposure values. It's meter measures the light reflecting off your subject and adjusts itself so it is perfectly exposed .. not too light and not too dark. But problems will arise if the reflected light is really bright, an example being a sandy beach, a polar bear in a blizzard or your favorite bride, all dressed in white while standing in front of the white marble altar. It will also try to correct for really dark scenes or subjects, the classic example being the black cat in the coal bin.

Let's examine a very light subject.

I used these lovely white sea shells for this example. The camera see bunches of light coming in and says to itself, "Oh, I'm going to adjust my settings to take a perfect average picture". And this is what happens


The photo is under exposed. To the camera it is perfectly exposed. It measured the light coming in and made adjustments for an average amount of light. What the camera operator needs to do is say, "Bad camera!! It needs more light!" This is where you take over. If you have manual override you merely let more light enter the camera ... a slower shutter speed or a larger aperture (fstop). If your camera has picture modes search for the one that is for snow, or beach, or backlit, or something ... you may actually have to consult your manual for this info.

By changing my settings to allow more light into the camera a better approximation of actual scene is captured ...


The little graph in each picture is representative of how many pixels in the picture are in each tonal range ... darker pixels to the left side and lighter pixels to the left. As you can see in the top graph, everything is pushed to the dark side, Luke. In the second shot they are more evenly distributed with many more pixels in the lighter range. This is good.


The camera does the exact opposite with dark scenes and subjects. It thinks to itself, "Gee, there's not much light coming in so I better increase the exposure." The end results are an over exposed picture. We, the photographic geniuses, know that this is wrong. So we make the camera submit to our wishes and command it to cut back the exposure. A faster shutter speed, smaller aperture or some combo of both.

The overexposed dark subject


And the compensated, correct exposure


So keep in mind:
If the subject/scene is light, white, bright; don't let the camera underexpose the shot ... compensate by going manual and decrease shutter speed or use a larger aperture or a combination of both. No manual available ... check your camera's scene modes for beach, snow or backlit.

If the subject/scene is dark, black, spooky; the camera is going to overexpose. Compensate by going manual and increasing shutter speed, using a smaller aperture or a combo of both. No manual override check your scene modes for night scene, fireworks or black cat in a coal bin setting.

Remember, the camera is trying it's best but it has no idea what is correct for every subject unless you tell it. Left to it's own devices, it can and will disappoint at times.

The end.

(There will be a short quiz next week but it won't be graded)






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Arrow 20 replies Author Time Post
Reply Photography 101 ... Exposure and Metering Quirks (Original post)
MichaelSoE Jul 2013 OP
CurtEastPoint Jul 2013 #1
ManiacJoe Jul 2013 #2
Major Nikon Jul 2013 #3
Mira Jul 2013 #4
rdking647 Jul 2013 #5
postatomic Jul 2013 #6
sir pball Jul 2013 #7
ManiacJoe Jul 2013 #9
sir pball Jul 2013 #13
Blue_In_AK Jul 2013 #8
ManiacJoe Jul 2013 #10
Blue_In_AK Jul 2013 #11
ManiacJoe Jul 2013 #12
Celebration Jul 2013 #17
Blue_In_AK Jul 2013 #19
Major Nikon Jul 2013 #14
Locut0s Jul 2013 #15
JohnnyRingo Jul 2013 #16
Celebration Jul 2013 #18
a la izquierda Aug 2013 #20

Response to MichaelSoE (Original post)

Wed Jul 24, 2013, 04:40 PM

1. Excellent lesson. A difficult concept to master.

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Response to CurtEastPoint (Reply #1)

Wed Jul 24, 2013, 05:38 PM

2. It is not as hard as it seems.

The camera wants to average everything out to a nice medium gray. In general, this tends to work well. However, if your subject is more towards the edges of the exposure scale (the white shells or the black brush), the camera will need some hints from the user to keep the subject's color near the edges of the exposure scale.

The onboard computers with their exposure databases have come a long ways, but they still need some help sometimes.

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Response to CurtEastPoint (Reply #1)

Wed Jul 24, 2013, 06:01 PM

3. Just carry a grey card in your photo bag

Set your camera to manual exposure mode, meter on the grey card positioned in front of your subject parallel to your lens (not tilted). Remove the grey card, and take the picture.

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Response to MichaelSoE (Original post)

Wed Jul 24, 2013, 07:25 PM

4. THANK YOU - I am thrilled you are taking the time

to do this.
Please keep it up.

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Response to MichaelSoE (Original post)

Wed Jul 24, 2013, 09:41 PM

5. another trick

if you dont want to use manual exposure
use the exposure compensation button on your camera

if its a bright scene add a positive ex comp value
if its a dark scene use a negative value.

its a little trial and error/experience but it comes in handy

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Response to MichaelSoE (Original post)

Wed Jul 24, 2013, 10:02 PM

6. Very good tutorial

I actually go old school and use a light meter when I want a good exposure. Otherwise I usually just correct in post, if I can.

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Response to MichaelSoE (Original post)

Thu Jul 25, 2013, 01:45 PM

7. Important if you're shooting Velvia, but I just wing it with digital.

Knowing the difference between what the meter sees and the actual scene is indeed crucial for an extremely unforgiving media like slide film, or for properly working the Zone System. I still have my greycard from B&W 101 and know how to use it, with spot metering if need be.

But with my 5100 I just shoot Program or Aperture, EV -2 and then pull the lightness up in postprocessing. Sensors these days have such lovely shadow detail that it's really not worth the extra time in the field to work out the perfect exposure; I feel it's better spent getting more shots instead. Just my 2 though.

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Response to sir pball (Reply #7)

Thu Jul 25, 2013, 05:57 PM

9. Seems like this would generate more digital noise than necessary.

But with my 5100 I just shoot Program or Aperture, EV -2 and then pull the lightness up in postprocessing. Sensors these days have such lovely shadow detail that it's really not worth the extra time in the field to work out the perfect exposure; I feel it's better spent getting more shots instead. Just my 2 though.


Normally you would want to go the other way: slightly overexpose the image (since there is tons of data room in the highlights) and darken the picture in post-processing.

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Response to ManiacJoe (Reply #9)

Fri Jul 26, 2013, 12:38 PM

13. Not (for me) at low ISOs and a couple of stops

At 6400/-4 in a dark bar it gets pretty nasty, but I almost never switch from 100 and -1.3 (I thought it was -2, but I was wrong...shows how often I change that!) so it's really a nonissue. I really hate the abrupt clipping when digital highlights blow out, and it seems that even the most sophisticated matrix metering tends to wipe out a lot of the sky. For a shot where I'm taking the time to think or watch the histograms, and definitely with film, nothing beats correct exposure - but I'm willing to compromise a wee bit for convenience's sake most of the time.

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Response to MichaelSoE (Original post)

Thu Jul 25, 2013, 04:41 PM

8. I had a heck of a time getting exposures right

while we were on vacation. Large backyard swimming pool with white concrete around the outside, while my subjects were sitting in the shade. If I got the pool right, the people vanished into black, and if the people were right, everything else was blown out. Can't really do multiple exposures with moving subjects either.

The shots are mostly for memories, not perfection, so I'm not too concerned, but high-contrast situations always give me fits.

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Response to Blue_In_AK (Reply #8)

Thu Jul 25, 2013, 05:58 PM

10. This is where gradient ND filters can help.

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Response to ManiacJoe (Reply #10)

Thu Jul 25, 2013, 06:32 PM

11. Which I don't have but probably need. :)

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Response to Blue_In_AK (Reply #11)

Thu Jul 25, 2013, 06:35 PM

12. I am in the same boat.

I have the rectangular filter holder but no filters yet.

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Response to Blue_In_AK (Reply #11)

Tue Jul 30, 2013, 08:40 PM

17. What do you use in post processing?

Photo Director handles this issue really well--you just highlight the portion you want to change and you can lighten or darken just that portion. I just assumed most programs would do this. I don't have that much experience with post processing, but I use this capability on Photo Director quite a bit.

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Response to Celebration (Reply #17)

Wed Jul 31, 2013, 01:22 PM

19. I have PaintShopPro, and, yes, I can usually fix things in post-processing,

but it would be nice to have it good out of the camera.

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Response to Blue_In_AK (Reply #8)

Fri Jul 26, 2013, 11:13 PM

14. Use a flash to decrease contrast

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Response to MichaelSoE (Original post)

Sat Jul 27, 2013, 08:33 PM

15. Fantastic work MichaelSoE, thank you for this!...

This is JUST the kind of thing I need to be working on. I have something of a handle on composition and, lighting etc but getting the right exposure still bothers me. Thanks

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Response to MichaelSoE (Original post)

Tue Jul 30, 2013, 07:44 PM

16. Thanx... I learned a thing or two.

But that's why I love this group. The collective knowledge and experience here is it's own reward.

I believe I've become a considerably better photographer only because of those who post here.

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Response to MichaelSoE (Original post)

Tue Jul 30, 2013, 08:41 PM

18. Thank you

I definitely checked recommend for this thread.

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Response to MichaelSoE (Original post)

Thu Aug 1, 2013, 06:41 AM

20. Danke!

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