Exposure Bias - Setting Issue

[Snooks]

Just over the last few days an issue has arisen and it is obviously a setting. I think that I have resolved it but I would like to be sure by gaining some input because I still do not totally understand it all.

A few days ago I took some photos and all was good. The equipment in use was:

Nikon D200
Nikkor 18-55mm f/3.5-5.6

I took some photos of Roses, they were quite bright and over exposed and it was reported to me the Exposure Bias was indicated as +3 in the Exif Data. I think that is when and why I made the change, but I can't remember exactly WHAT I changed :(

So I believe, I think, I probably or I may have altered the settings. (Covered all bases LOL)

I took some images 2 days ago, it was cloudy but not that bad. The Cockys came home for a snack and Taylor had a dozen or so within 5 foot of where I was kneeling. I took some photos in Full Auto and I also took a couple on Shutter Speed priority and also Aperture priority so I could compare the different DOF's and just see what results were thrown up.

The images when uploaded into the computer looked very very black and very dark. Certainly different from normal. I took 39 in total this is just a few in a screen clip to show the computer screen and how dark they are on the screen and when you open the files.

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When I opened in RAW, if I hit Auto Adjust on colours they brightened up immediately and were ok. I edited one as normal and saved as a jpeg to compare in the screenshot. So the issue was easily resolved but obviously is an issue.

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The Exif Data varied and showed various amounts between -1.5 and one was as high as -9.

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The problem is that I am not sure exactly what setting I need to adjust to alter of affect the exposure Bias.

That term is not what I see in the settings. I did do a manual "Quick Reset" but although many things changed, I do not believe that this issue did. The uploads of any images taken then were still very under exposed.

I have been through the Settings Menu, focused on the Exposure / Metering Branch and I have checked, altered and fiddled with settings. All seems to be correct and complient with the recommendations Ken Rockwells Manual suggests. A tests photo outside seems correct but today is very sunny.

I just don't want to go out sometime, see a great opportunity and then have it spoilt by this issue again. As such, I think running it by the Forum will probably be the easiest way to fix the problem because i'm sure someone has had this issue before. I'm really sure it's a setting...... but which one?

Any advice would be appreciated :)

[nardes]

On my Canon DSLRs, you can rotate the Rear Wheel when in either P, Av, T Mode (there may be more but these are the ones I use).

This has the effect of increasing or decreasing the camera suggested exposure by + or - the stops you set.

I have set my Adjustment Steps to 1/3 of a stop, so each turn of the Rear Wheel in one direction would decrease the exposure by -1/3, -2/3, -1, -1 1/3, stops etc.

Turning the Rear Wheel in the other direction would increase the exposure by +1/3, +2/3, +1, +1 1/3 stops etc.

It is easy to accidentally turn the Rear Wheel and this stays locked in, even if you power off the camera, so you have to manually turn the Rear Wheel to set the Exposure Compensation back to "0" i.e. what the camera reading is.

Cheers

Dennis

[ameerat42]

Gosh! - A bit of a mystery tour, Snooks... :scrtch:

Easiest first: RAW and Auto Adjust. This shows the latitude of tones a raw file can have. (Good to remember.)

2nd: How to set Exposure Compensation to 0: see P 72 of the manual, or page 72 of this link. (http://download.nikonimglib.com/archive2/wA0rL00RpGgd01x3Hi344FzbGJ59/D200_NT(En)05.pdf) That's shown as "Exposure bias" in the EXIF.

3: The mystery: Going on what the conditions were - cloudy but not too dull and using one of Auto/Av/Tv - I cannot explain the results you have shown.
I assume the lens is fully compatible with the camera ("CPU lens", I think they call it.)

Well, See P72 of that KR manual to set the Exposure Compensation to 0.

After that, try to simulate the shots of the cockies, no matter what the light conditions.
(Use a white folded cloth or so in the middle of the frame.)

The frame you showed is certainly under-exposed by a few stops.
Your EXIF shows CW Average for metering, so leave it at that first. I can't believe that
the metering threw the settings off by so much. See if you can get more "normal" looking
shots under these controlled conditions.

Change the mode to Tv (shutter) and later Av (aperture) priority for another series of shots.

At some time, try Manual exposure. You will know when the exposure is "about right" by the
position of the indicator in the LCD panel as you change the shutter/aperture/ISO. I suggest
that you leave the ISO set (say 200) for each series of shots UNTIL you do s series on ISO change.

Best if you just try to "re-do" the "cloth-cockies" first and post just that up for analysis.

[fillum]

A couple of 'theories'...

Check that you don't have exposure bracketing enabled (not sure how this works on D200 - check the manual)

Check that you aren't accidentally pressing the +/- button (near the shutter I think) when rotating the dials.


It's a good idea to check the histogram, at least periodically, to confirm that your exposures are at least reasonable.



Cheers.

[Tannin]

Simple rule: the camera wants to turn everything medium-grey. If you are taking a picture of a snowfield, you need +ive EC to make it brighter than the camera thinks (snow is supposed to be white). If you are looking at a coal mine, you need -ive EC to make it black.

[Snooks]

Thank you so much to everyone for the assistance and I am 100% confident that the issue was fixed.

when taking photos I think i have mentioned that I turned the rotating wheel at the rear whilst doing a bracket, so it would make minor adjustments and I can compare or choose what image is best. At some stage I have also, either intentionally and i cannot remember or accidentley with my big hands, rotated the wheel whilst i had the little +/_ Button depressed and I subsequently changed the Bias. When i just checked it I was still at +3.5 .

So i just went outside, a bright sunny day, on full auto a quick snap of the rock that the Cocky was sitting on and also a rose bud


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The exposure bias shows as

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So thank you everyone, the issue is fixed and i feel so relieved. I was starting to panic and think that I had changed something that could never be reverted back to normal.

Now I feel awesome and i'm looking for something to take a photo of :tog:

[ameerat42]

H:party7::party7:ray for working it out. I take it no white cloths were harmed
in the meantime :D

[Snooks]

H:party7::party7:ray for working it out. I take it no white cloths were harmed
in the meantime :D

Not until I got upset and blew my nose :(

[arthurking83]

Good to see you worked out how to sort it.

2 points to note(when shooting). .. actually it may well end up a few more points to note, but that's just the way it usually ends up for me .. I waffle on sometimes.

1/. take note of the exposure meter in the viewfinder. there is a 0 point and then dots either side of it.
By default(in the D200's day) any dots in the meter on the right indicate -ve exposure compensation, dots on the LHS of the zero mark = +ve exposure compensation(compensation = bias).

so look for the meter reading at the bottom of the viewfinder. On the far left you should have meter setting(ie. spot, centre or matrix), then as you move to the right, it'll be shutter speed, aperture and then close to centre is the meter indicator. , then ISO and whatnot.

1/. (a) choose your metering mode wisely!! Nikon have given you a very conveniently places meter flip switch toggle, to go from one to another quickly by feel.
I tend to use spot almost all the time, but when I'm lazy I feel like switching to matrix. I've only ever used centre a few times, mainly testing/fooling around. The part (a) is then related to the next point ...

2/. having worked what metering mode works best for you, then read Tannins' comments re exposure compensation based on the colour of your scene!
Be a bit aware of what it is that's actually being metered.
In a Nikon camera matrix is supposed to be meant to meter the whole scene, but in reality there is a weighted component to some parts. I can't remember the exact numbers, but it reads the entire scene, but then places more importance on the central part of a scene(I think it assumes a person is there so wants to help get a non too dark exposure of the person(that may or may not be there).
Either way, I never trusted any other than spot metering mode.
But there's a small catch. You have to do a bit of thinking, estimating and calculating to get it to work for 'ya properly .. most times.

If it helps, I did a small(small for me, but tedious/long for most folks! :p) write up on how modes work, how to setup/read and 'meter' correctly so that the camera exposures close to ideally.

See this thread (http://www.ausphotography.net.au/forum/showthread.php?132254-Camera-metering-what-it-s-doing-and-why-it-s-dumb&highlight=exposure+metering)
It basically tells you that colour = exposure .. what Tannin said. white is brighter, so compensate 'brighter'.
But it's also important to note that white may not be white.
eg. a white cocky having just rolled around in muck may not be 'quite bright white'. Young tin lid, in full sunlight wearing a freshly washed white t shirt is probably brighter than white.
The term white is a relative thing, and changes. As you get experience you instinctively tune the exposure to suit the scene.

Think back to how you can rotate a dial and it sets exposure compensation(bias.. but I prefer comp!).
This feature is called 'quick compensation', and can be turned off, but I always recommend to leave it on. You can also change the way it compensates with the direction of rotation too.
When using spot metering, the size of the subject in the frame makes a huge difference to how accurately it measures it's colour. Smaller = less accurate.
So take the cocky scenario again.. if you had a 500mm lens and were 5meters away, the cocky would have been large in the viewfinder. spot would have given a very accurate colour reading(ie. exposure).

For a cocky in amongst shadows I usually shoot it neutral(have done many times, its exposure usually good. But then the lens used comes into the mix too, I have a very dark 500mm lens, that prefers +ve exposure for exposure correctness, so I'll shoot that lens +0.3 Ev, ie. one click of the rear dial when in aperture priority mode to the left.
Remember by default, left click on a Nikon = more bright(+ve) right click = -ve compensation.
Because you mentioned clicking the rear dial, I suspect that you primarily use Aperture priority mode?
This is usually how it works.
If you use Shutter priority mode(and don't disable quick compensation), then adjusting the front dial is the quick compensation variable.

So you see the cockatoo, you zoom in, it's about 1/2 the height of the vf frame, you're in [A]perture priority mode, its full sun so it's white is very bright, (before you take the shot) you quickly glance at the meter in the vf (it shows no dots, so it's set to 0 compensation), you quickly click the rear dial 2 clicks to the left (which set +2/3Ev compensation), and what all this does is expose the cocky a bit brighter than it would otherwise be, but all the surrounding area isn't black!
All that takes literally a split second, maybe less than half a sec.
if the cockatoo is too bright(ie. it's lost some fine detail in the feathers) you then use your software to reduce the highlights a very small amount.

[Snooks]

@ AuthurKing83

Thank you so much for this very detailed explanation. I will read and re-read this and then actually go through it again with my camera in hand so I can understand it fully. (It's late now and I daren't wake the wife up turning lights on).

What I read will certainly be very helpful and thank you for taking the time to provide such a detailed and informative post. I am sure it will help me a lot :)

Cheers.