Need some help/ideas with digi rebel.

[Glaive]

Well this is a plea to all photo genuis peeps.

Today I went out shooting, 4th day in a row, and I set my ISO on my rebel down to 100. <Much better than the 1600 it was on. So now the pictures are much cleaner. However I hit a few spots where lighting was not visibly different than others and yet I ended up with Darker to black pics <same lense>. I hope some one can help me understand why via the metadata below. Thank you in advance.

Good pic meta data:
Camera
Make Canon
Model Canon EOS DIGITAL REBEL
Orientation upper left
X resolution 180
Y resolution 180
Resolution unit 2
Primary chromaticities (0.64,0.33,0.21,0.71,0.15,0.06)
YCbCr coefficients (0.299,0.587,0.114)
YCbCr positioning centered
Whitepoint (0.313,0.329)
Exposure time 1/100 s
F-number 3.5
ISO speed ratings 100
Shutter speed value 0.010000 s
Aperture value 3.61472
Exposure bias value 0
Max. aperture value 3.61472
Metering mode Pattern
Focal length 18 mm
Exposure mode Auto exposure
White balance Auto white balance
Scene capture type Standard


Bad pic meta data:
Camera
Make Canon
Model Canon EOS DIGITAL REBEL
Orientation left lower
X resolution 180
Y resolution 180
Resolution unit 2
Primary chromaticities (0.64,0.33,0.21,0.71,0.15,0.06)
YCbCr coefficients (0.299,0.587,0.114)
YCbCr positioning centered
Image
Whitepoint (0.313,0.329)
Exposure time 1/100 s
F-number 5.6
ISO speed ratings 100
Shutter speed value 0.010000 s
Aperture value 4.97086
Exposure bias value 0
Max. aperture value 4.97086
Metering mode Pattern
Focal length 54 mm
Exposure mode Auto exposure
White balance Auto white balance
Scene capture type Standard

[Glaive]

Well after doing some research I would venture to guess it has to with fnumber/fstop?
The 18mm focal distance shot had an fstop of 3.5
and the 54mm focal distance shot had an fstop of 5.6

Which translates to 1 1/2 fstops roughly, which in turn makes for 3x as much light getting to my sensor?

No one responded to teh initial question, please if you know the answer tell me if I am correct in my assumption.

Thanx

[jennigypsy]

<ow! all that info made my brain squeek>


LOL
Sorry I'm no help.....maybe FINZ would be the man to ask.

[Glaive]

Lol I'd agree JG.
Fortunately with simultaneous reading of my manual and a camera/photography terms web page I was able to discern where I went wrong.

I now know that my camera talks to me and what to do when it tells me I am messing up the expossure of a picture.

PS JG you think that hurts your head try reading about the actual deffinition of fstop lol... + +

[Glaive]

What's funny Finz I was shooting in Tv mode and didn't know that when the shutter time was blinking in the display that the exposure was off. So it came down to the darker pic needed a lower shutter speed and the camera told me so I just didn't know at the time what I have learned in the last day.

I'll post the two images unedited below.
Ty for taking the time to look. just have to wait for aseedcee to cache the thumbnails from the raws and then to remember which I used as examples.

[Glaive]

I can change the exposure within photoshop by about 1.5 and they appear to be exposed the same. Even the better one is under exposed, but I can clean it up, not that I would need to now that I have learned where I went wrong.

edit:
Upon looking at them now it seems photoshop compensated for my snaffu somewhat. pre photoshop the bottom one looks black, that is when the raw file is viewed in asee dcee, while teh top one looks as is.

[Glaive]

Well since I have your attention Finz. When you get your amazing shots I know that you have used your 75-300<at least once> to full advantage for depth of field. Did you manually set your apeture to get the effect or was it just the lense?

I am still working on the iso setting vs fstop and shutter speed. My head almost hurts lol.

Just curious Finz since I know you have a D20 now, have you looked into photoshop CS? If not you may want to have a look, considering what it can allow a bungler like me to do.

[Glaive]

Okay all the pictures I have shot have been in TV or shutter priority mode.

So I just need to pay attention to when the shutter priority/time is flashing in the view finder, which lets me know that the exposure is under.

As for the exif data being incorrect I'm not sure those were the exact pictures I pulled the info off of originally. I was just hitting properties in asee dcee on the THM file.

However it seems you have answered my questions. Actually within photoshop rather than using the highlight shadows option it is better to use the exposure control when converting the raw file it makes for less noise/artifacts.