Old 07-24-2005, 12:48 AM   #1
mtrails
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Default Dusk/Dawn lighting...

I know there is a previous thread around here somewhere, but I couldn't find it (or gave up looking!), but anyway...

Here is a photo I took this morning, just as the sun was peeking over the land.

http://www.railpictures.net/viewreject.php?id=148674

It was rejected for poor cropping, underexposed, and distracting shadows:

This is my first attempt in low-light conditions, and I thought I set up a pretty cool shot. Cropping I can work with. Underexposed? Well I had a +.03 light level adjustment set on my camera, and when I edited the photo before submitting, I actually compensated, since it looked over-exposed. I must have gone too far? The shadows... Yeah I know.

I'm just looking for opinions.

Thanks!
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Old 07-24-2005, 12:59 AM   #2
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I like the cropping, though maybe a little off the bottom might be in order. It does seem a little under exposed, but nothing some editing couldn't fix. However, I think they may have you on the shadows. Having the side of the first engine lit up, but the front in shadows is a little weird. I have a similar picture of a Metra cabcar I took in the early evening that had the same problem. Even though the side looked great all lit up by the late afternoon sun, I knew the dark front of the car would be a deal-breaker, and didnít submit it.

Itís a great composition though. Iíd go back there and try again.
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Old 07-24-2005, 04:01 AM   #3
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Based on the histogram, it is slightly underexposed. Check out the attached image in which I messed with the histogram and upped the saturation a tad (I had to save at a leser setting to allow for an attachment, but you can see the difference in exposure when it's lightened).

I recently had a dusk shot rejected for being underexposed, even though I had the ISO set at 400. Post-processing allowed me to lighten it enough to make it here:

Image © Chris Paulhamus
PhotoID: 112983
Photograph © Chris Paulhamus


I really like the composition of your shot. I think had that train been there 30 minutes or so later, it would have been ideal...
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File Type: jpg sf_gp60morning.jpg.54676..jpg (174.9 KB, 206 views)
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Old 07-24-2005, 01:12 PM   #4
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Thanks Ween. You know, my photo was about as light originaly, before I edited it, because it almost looked like the photo was "washed" due to the light compensation settings. Though it wasn't much, it just didn't look natural for the amount of true light on the subject(s). I had also upped the saturation, since the camera automatically adjusts the white balance, and the golden sunlight looked more white.

Quote:
Originally Posted by Ween
I really like the composition of your shot. I think had that train been there 30 minutes or so later, it would have been ideal...
There would have been more light, but because of the sun angle, the nose would not see sunlight until about 3 or 4 o'clock. I was set up for trains coming from the West (as the one in the photo is from the East), and that little patch of sun sneaking down onto the tracks set the shot for me. I think I'll try a similar shot in the same area, and hopefully with about the same light, but try to get less of a wedge, so the shadowed nose won't be as visible. I really like the golden trees in the background.
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Old 07-26-2005, 04:33 AM   #5
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Yo Ween,
ISO is Film speed. It doesn't have much to do with exposure, but more often with the overall quality of the photo. F-stops and exposure times are what you have to look for. Usually a low aperature such as F2.9-F3.2 with a quick shutter speed will wok good for dusk and early evening photography. Case in point:
Image © John Witthaus
PhotoID: 99177
Photograph © John Witthaus


Image © John Witthaus
PhotoID: 100823
Photograph © John Witthaus
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Old 07-26-2005, 05:14 AM   #6
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Quote:
ISO is Film speed. It doesn't have much to do with exposure
I thought ISO was tricking the camera's image processor into thinking there is more light than there actually, an internal correction for low lighting, if you will...
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Old 07-26-2005, 02:06 PM   #7
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Quote:
Originally Posted by StL-rail
Yo Ween,
ISO is Film speed. It doesn't have much to do with exposure, but more often with the overall quality of the photo. F-stops and exposure times are what you have to look for. Usually a low aperature such as F2.9-F3.2 with a quick shutter speed will wok good for dusk and early evening photography. Case in point:
Image © John Witthaus
PhotoID: 99177
Photograph © John Witthaus


Image © John Witthaus
PhotoID: 100823
Photograph © John Witthaus
I used to try the 400 ISO in dim light, but it just created too much grain.

StL-rail, would you suggest (in a general context) use a shutter speed > 1000? I haven't been able to command the glint shot or silhoutte.
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Old 07-26-2005, 02:16 PM   #8
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What Is... ISO
ISO Sensitivity Auto; ISO 100, 200, 400, 800 equivalent

ISO sensitivity expresses the speed of photographic negative materials (formerly expressed as ASA).

Since digital cameras do not use film but use image sensors instead, the ISO equivalent is usually given.

What ISO denotes is how sensitive the image sensor is to the amount of light present. The higher the ISO, the more sensitive the image sensor and therefore the possibility to take pictures in low-light situations.

And, where you would have needed to physically change to a different roll of film if you wanted a different ISO speed, digital technology allows you to simply dial one in. In this way, you can record images taken at different ISO speeds on the same memory card.

ISO Speed & Exposure

ISO speed affects the shutter speed / aperture combinations you can use to obtain correct exposure.

Suppose your digital camera's light meter warns you there is not enough light to correctly expose a scene. You could use the on-board flash, but let's suppose again it's not allowed (like in a concert or indoors recital).

You would then need to use a higher ISO. Set on "ISO Auto" mode, your digital camera will automatically select a higher ISO. Otherwise, you can manually select the next higher ISO and see if the increased sensitivity allows you to obtain a correctly exposed picture. If it does, you can now take a correctly exposed picture.

Similarly, if you find the camera is using a shutter speed that is too slow (1/60 sec. and slower) to handhold the camera steady and shake-free (thus resulting in blurred pictures), and you cannot open up the aperture anymore, and you do not have a tripod or other means to hold the camera steady, and you want to capture the action, etc. etc. -- then you might select the next higher ISO which will then allow you to select a faster shutter speed.

ISO Speed & Noise

However, all this increase in sensitivity does not come free. There is a price to pay with your image appearing more noisy.

See, when you boost the sensitivity of your image sensor by selecting a higher ISO, the image sensor is now able to record a fainter light signal. However, it is also true now that it will record fainter noise, where noise is any signal that is not attributed to the light from your subject. Remember that an image sensor is still an analog device and it generates its own noise, too! The increased sensitivity allows the image sensor to record more light signal and more noise. The ratio of light signal to noise (S/N ratio) determines the "noise" in your resultant image.

An image sensor is usually calibrated so that it gives the best image quality (greatest S/N ratio) at its lowest possible ISO speed. For most consumer digital cameras, this value will be expressed as ISO 50, ISO 64 or ISO 100. A few digital cameras use ISO 200 as their lowest ISO speed.

Just as with its film counterpart, an image sensor will exhibit "noise" (comparable to "graininess" in film) at the higher ISO speeds. Unlike film, where graininess can sometimes contribute to the mood of the image, noise produced by an image sensor is undesirable and appears as a motley of distracting coloured dots on your image.

ISO Speed & Image Sensor Size

The size of the image sensor determines the ISO speed range that a digital camera can use without suffering from undue noise. One reason for this is because the pixels on the larger image sensor can be larger and therefore receive more light, and thus have a greater signal-to-noise (S/N) ratio (for more information on noise, see our tutorial: What Is... Noise?).

If we take two image sensors, each with 4 megapixels resolution, but of different sizes, the 4 megapixels image sensor that is smaller will exhibit more noise at higher ISOs than the larger one.
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Old 07-26-2005, 09:30 PM   #9
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Wow, I just wanted opinions on my photo, and I got an in-depth ISO lesson!

Sweet!
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Old 07-27-2005, 06:12 PM   #10
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That is a nice enough picture, and it cleans up pretty well as shown by Ween's treatment. But distracting shadows? Sounds like someone is trying a little too hard to be a photo critic on that one. Reaching a bit, personally.
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