My XTi... Exposure Problem?

jsedlak

I am trying to find out a way to test if my XTi has an exposure problem or if I am doing something wrong. Yesterday after work ended (5:30) I attempted to take pictures of the electrical power grid next to us as it got lit up by the falling sun... they all came out quite a bit dark until I adjusted the shutter speed so that the meter would be at +1.

Click for full resolution (Very large). The area was a lot brighter than the images display. Indoors I seem to have to use ISO1600 or the images won't come out bright enough, or they will come out too blurry (low shutter speed).

Shutter Speed: 1/400s
ISO: 200
FStop: 5.6


Shutter Speed: 1/200s
ISO: 200
F-Stop: 5


Any help is appreciated... I just got the camera and am not sure what to do. :cry

~John

Edit, Should probably add these are taken in JPG mode. Maybe it is just time to switch to RAW? *oh noes plz not yet!*

pathfinder

John, I cannot evaluate the exposures of these images without more information.

ISO 200 and shutter speed are insufficient to determine exposure. What what the aperture used? Were these images shot in Av, Manual, Tv or Program modes??

These images look rather like an exposure of a shaded area and a very bright sky. One of these areas is NOT going to be optimally exposed with only one single exposure. The contrast range is just to large. These look like a fair compromise for the shaded areas.

As for requiring IO 1600 indoors, again not sure what you are doing. I can shoot with ISO 100 with a point and shoot if I am careful and the light is adequate indoors. With a DSLR and a good lens, you can usually shoot with ISO 400 or 800 pretty easily, unless your lens is very slow.

Sunny 16 rules for outdoor exposure, would suggest that at ISO 200, a bright sunlit subject, with an aperture of f16, would need a shutter speed of about 1/200th.

jsedlak

The thing is that although the parking lot wasn't getting hit directly it was definately brighter than it is showing up in the pictures.

F-Stops (Thanks for reminding me, I knew I forgot something) were 5.6 and 5 respectively. Indoors I use the 50mm at 1.8.

Is there a test I can do to allow a better/easier judgement?

Jeffro

jsedlak wrote:

The thing is that although the parking lot wasn't getting hit directly it was definately brighter than it is showing up in the pictures.

To tell if the exposure was correct, or if there was a problem, it would help to know what metering mode you used.

The parking lot will be darker, if the sky is metered. A camera just can't expose the sky (highlights) and the ground (shadows) both correctly, as pathfinder said. You pretty much have to choose which you want more correct or invest in a graduated nuetral denisty filter set or take a picture of the ground at it's proper exposure, then one of the sky at it's proper exposure and merge the to with PS trickery.

And the camera will not see light as well as your eyes.....it can't.

pathfinder

According to the Sunny 16 rules for estimating outdoor exposure, shade is three f stops darker than a frontal sunlit subject. SO, at ISO 400, shutter speed of 1/400th suggests an aperture of f16 for the sunlit area, and three stops lighter for the shaded area or f5.6

So your exposure was about right for the parking lot with ISO 400. Digital sensors have very little latitude for the correct exposure, and trying to capture deep shade and sunlight within the same frame is a very difficult road to hoe.

Graduated Neutral density filters can be sued with a camera on a tripod, but are not very useful for handheld snapshots. You can also shoot two frames at different exposures and blend them in PS, but this requires planning in advance also. Shooting in RAW and creating two jpgs at different exposures is also possible.

jsedlak

Weird. I guess I went a little nuts when I saw the shots. With all this talk going around about the XTi having exposure problems, I am watching my results very closely.

erich6

They look reasonable to me. You needed the + exposure compensation in the first one because of all the sky. The camera meter will try to make the average look like a midtone grey but in this case the sky should be part of your highlights.

You should be able to handhold the camera with no problems with 2-4 times longer exposure than you showed here (I'm assuming you are using the kit lens).

One thing you can do is to use evaluative metering. In that case the camera will set the right exposure for the autofocus point you have selected.

Erich

wxwax

You may have heard that digital cameras have a narrow "dynamic range."

Your two photos illustrate this perfectly.

jsedlak

wxwax wrote:

You may have heard that digital cameras have a narrow "dynamic range."

Your two photos illustrate this perfectly.

Care to explain?

erich6 wrote:

They look reasonable to me. You needed the + exposure compensation in the first one because of all the sky. The camera meter will try to make the average look like a midtone grey but in this case the sky should be part of your highlights.

You should be able to handhold the camera with no problems with 2-4 times longer exposure than you showed here (I'm assuming you are using the kit lens).

One thing you can do is to use evaluative metering. In that case the camera will set the right exposure for the autofocus point you have selected.

Erich

I definately can hold it fine down to about 1/30s and then my hand isn't steady enough. I am using the kit lens for this shot.

And I have it set to Evaluative Metering.

mr peas

Are you sure you're metering from the same parts? If you meter (point at) from the sky it will turn out darker in the foreground, and if you meter from the dark foreground, it will make the entire photo brighter.

You can meter off diff objects by pressing the button labeled * near your right thumb. Press that before focusing on something but have it pointed to where you want to the camera to meter off, then focus and shoot.

Its easy for a new shooter to not know that you can 'meter off' diff objects. I think thats what you're doing. I believe in your first dark photo you pointed at the sky. Then in the second you pointed at the foreground.

Really play with the button labeled "*" near your right thumb on the left side. I think you will see that its very helpful.

BrianJA

Hey... OT, but is that in Rahway? It just looks really familiar.

If it is, the shop that did my stereo system used to be in there and has moved to the new building in front.

jsedlak

BrianJA wrote:

Hey... OT, but is that in Rahway? It just looks really familiar.

If it is, the shop that did my stereo system used to be in there and has moved to the new building in front.

Yep!

800 New Brunswick Ave...

BrianJA

jsedlak wrote:

Yep!

800 New Brunswick Ave...

Bingo... can't believe I recognized that.

Thanks for the confirmation.

wxwax

jsedlak wrote:

Care to explain?

Sure.

Let's start with film, for the sake of comparison. Film used to make prints (not slides) has a lot of exposure latitude. This means it can capture detail across a wide range of light - from fairly bright highlights to fairly dark shadows.

Digital cameras (and slide film) do not have a wide exposure latitude. If you expose for bright highlights, you usually lose shadow detail. If you expose for dark shadows, you usually lose detail in bright highlights. Digital sensors, so far, cannot handle the range of light from sunlight to shadows.

Your two photos are a perfect illustration. The first is exposed for the bright sky, and so the shadows lose detail. Your second is exposed for the shadows, and so the sky and metalwork are overexposed.

More technical people can explain with numbers.

People like me compensate by shooting in RAW. Or by shooting multiple exposures from a tripod and then combining them.

Shooting in RAW adds a couple of stops to your exposure latitude. But to take advantage of it, you have to make two exposures out of your RAW file (one for highlights and one for shadows) then combinne them in your computer using software like Photoshop or Paint Shop Pro.

The other way is to actually make two different exposures in your camera (again, one for highlights and one for shadows.) This gives you complete control of the scene. Again, in your computer you combine the two different exposures.

I see one risk with blending exposures. If you're not careful, the scene doesn't have enough contrast.

Read here.

And here.