# Nikon D90 not detecting exposure properly?



## coldmm803 (Apr 17, 2011)

Hi all, this is my first post. I'm relatively new to photography, got my D90 about a year ago.
How could I determine if my camera is or is not properly determining exposure?

I'm trying to learn some basics of photography and saw an article about the Sunny 16 rule. With my camera, I feel like the exposure would be awful at the setting suggested by this rule. Is the rule based on the camera facing the sun or away from it?

A few days ago on my way to work (7am) I took a few pics and to get what I feel is proper exposure I had my settings at ISO 250, f/6.3 and exposure 1/40. Are these setting reasonable for this photo?



DSC_1552 by coldmm803, on Flickr


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## shufti (Apr 17, 2011)

Hi. Read this through. I think it will answer your question and it's a great tutorial.
Understanding Histograms


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## shufti (Apr 17, 2011)

And the linked page towards the end of that explanation..
Expose Right


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## KmH (Apr 18, 2011)

Your D90 has 3 metering modes; Spot, Center-weighted, and Matrix.

Each has it's uses.

Spot is the most accurate, but it only samples about 2.5% of the scene. (see page 87 of your D90 users manual) 
Center-weighted can be set to sample using a diameter of 6 mm, 8 mm, or 10 mm (Custom Settings menu b3. See pages 87 and 178 of your D90 users manual)
Matrix mode samples, and averages, the entire scene.

Also on page 178 is menu b4, for fine tuning the optimal exposure in 1/6 EV increments  up to +- 1EV.

The sunny 16 rules is used only to get your exposure in the ballpark, and is not an absolute. Plus you have to adjust the exposure settings if you use a different aperture, which make understanding what a 'stop' is very handy.

In short, a stop is a halving or a doubleing.

You posted a photo that you made using the settings: ISO 250, f/6.3 and exposure 1/40

All 3 of the settings are the exposure. all of the following settings combinations would give *the exact same exposure* that ISO 250, f/6.3, 1/40 gave you.
ISO 250, f/4.5, 1/20 (ISO unchanged, 1 stop larger lens aperture, 1 less stop of shutter speed)
ISO 500, f/6.3, 1/80 
ISO 500, f/9, 1/40 
ISO 200,  f/5, 1/20 
ISO 200, f/7.1, 1/10

But there would be slight differences in how the different lens aperures would render depth-of-field (DOF), how effective shutter speed would be at stopping motion, and because of the ISO setting how much noise each exposure would have.

Many combinations of ISO, aperture, and shutter speed will give the same exposure, but only 1 of those various combinatioons will use settings that produce the DOF and motion stopping you want for the photograph.


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## coldmm803 (Apr 18, 2011)

shufti said:


> Hi. Read this through. I think it will answer your question and it's a great tutorial.
> Understanding Histograms


Are you suggesting that as long as my histogram is good to not worry about what the settings actually are? 

KMH, thanks for the response.
Maybe I should have added this to my first post. What throws me off about the sunny 16 rule is that at ISO 200, f/16, my shutter should be around 1/200.
The progression of 1 stop aperture and 1 stop shutter is:
ISO 200, f/11, 1/500
ISO 200, f/8, 1/1000
ISO 200, f/5.6, 1/2000
Unless my lighting conditions at 7am were way too dark for the rule to apply, I don't see how I can come close to a shutter speed of 1/2000...or 1/500 for that matter


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## shufti (Apr 18, 2011)

Yes, unless that's a barbed question. Obviously your exposure can be good but the image suffers from camera shake. The old rule for handheld is shutterspeed at least equals focal length mm. So a 50 lens is used minimum 1/50th sec. You have IS of some sort so 50 should be ok. Personally, more and more I find to double that rule.

If 1/50 is underexposed, raise ISO, open-up or maybe try a flash.


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## molested_cow (Apr 18, 2011)

Exposure reading is just a suggestion. Histogram is the result analysis. They are not directly related if you understand what I am trying to say.

It's like you go to a restaurant, asks the waiter to make you a suggestion. You can take it or choose your own. Then when you've tried whatever you eventually ordered, you can then judge if it was the right choice. The light meter is the waiter. Your taste bud gives you the histogram.


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## shufti (Apr 18, 2011)

Kudos to know and employ the sunny 16, cloudy 11, under a bush 4, or whatever you want to style it. But you have a camera with TTL metering and the histograms. If you're au fait with using a cameras metering modes, the histogram will ensure you have a decent exposure after a single try or a few. The histogram isn't necessarily 'result analysis'. Cameras have live histogram readouts that enable you to nail exposure before you take a shot.


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## OrionsByte (Apr 18, 2011)

At 7am, the sun's only been up for a half hour or so, right?  You're still in the "golden hour" at that point, and the "Sunny 16" rule isn't going to really be all that helpful because the sun is still being diffused by a lot of atmosphere.

As KMH mentioned, it's more of a guideline to help you get in the ballpark.  "Sunny 16" doesn't take in to account what your subject is, whether the things around the subject are bright, dark, reflective, or matte - your camera's meter does, at least if you're in matrix mode, which I'm guessing you are.

Go out at high noon on a bright sunny day with no clouds, set the camera on manual, ISO 200, 1/200, f/16.  Point the camera at something reasonably well sun-lit and shoot.  Chances are it's going to be close.  Change to aperture-priority mode, and depending on the scene, your camera will adjust the shutter speed to something it thinks is a better choice _in context_, but it will probably not be too far off from 1/200.

Also, whether your meter is working or not has no bearing on what the exposure of the photo looks like.  In other words, that shot you took at ISO 250, 1/40, f/6.3 would look exactly the same exposure-wise whether it was taken on your camera, my camera, or anyone else's camera, regardless of whether or not the meter thought the scene looked wrong.  I kind of got the impression that because the settings were not what you thought they should be based on the Sunny 16 "rule" that you thought there might be something wrong with your camera, but that's not the case.

Now on the other hand, if your camera told you that those settings would give you an on-the-nose exposure, and you snapped it and it was extremely over-exposed, _then_ you probably have a problem with your meter.


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## shufti (Apr 18, 2011)

@coldmm803 Sunny 16 is with sun roughly overhead/direct sunlight. Not into-the-sun/contre-jour, not 6/10s cloud and not in the shade.  It comes from film days with films possesing a certain latitude +- a stop. Digital raw does too. But set your picture style contrast at a minimum. The histogram is probably calibrated to JPG tolerance even if you shoot raw. Get as much of your image data in the highest two stops of the histograms as possible without clipping off the top. That's more than 50% of your camera's ability to encode the scene in terms of levels of luminance.


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## coldmm803 (Apr 18, 2011)

OrionsByte said:


> Also, whether your meter is working or not has no bearing on what the exposure of the photo looks like.  In other words, that shot you took at ISO 250, 1/40, f/6.3 would look exactly the same exposure-wise whether it was taken on your camera, my camera, or anyone else's camera, regardless of whether or not the meter thought the scene looked wrong.  I kind of got the impression that because the settings were not what you thought they should be based on the Sunny 16 "rule" that you thought there might be something wrong with your camera, but that's not the case.
> 
> Now on the other hand, if your camera told you that those settings would give you an on-the-nose exposure, and you snapped it and it was extremely over-exposed, _then_ you probably have a problem with your meter.


 
I hadn't thought about it that way...obviously. I think that was exactly what I needed to hear or read. I'll keep my eye out for a sunny day at noon and see what happens.
Thanks all :thumbup:


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