Variation in rendered photographs of the same subject

[dreed]

Whilst reviewing pictures with "c"ompare, I started to notice that some photographs are different even though they should be the same. Why should they be the same? Same shutter speed, same f-stop, less than a second apart - continuous shooting of a static subject. And indeed, the histogram is different.

Is this the camera's fault or is this Lightroom's fault?

I suppose "fault" is the wrong word to use but in some cases, the sky is quite visibly rendered a darker/lighter hue.

Is this a mechanical problem (slight variation in slow shutter speeds impacting exposure)?

Is this due to the sensor (warm vs cold)?

Or is it that Lightroom decides to render the same scene differently because the inputs are so slightly different and it's like a journey where after you take one right turn, instead of a left, the path is never the same (and thus the destination is always slightly different)?

Or is this just natural for (digital?) photography and that I'm noticing now is only because I've never pixel peeped to this level before?

[kevk]

Having auto white balance turned on in the camera can do this - each photo can have a slightly different WB even though taken seconds apart. Does Lightroom show a different Temp and Tint for each of the photos you are talking about?

Kevin

[dreed]

ok, this is going to sound even stranger ...

With a pair of photos, viewing them with "fit on screen" with compare always shows the one on the left to be lighter, in certain aspects, than the one on the right. I even swapped the photos around.

If I view them one at a time, in any other mode, they appear identical. Even the histograms are as far as I can tell, identical.

I suppose another aspect of this is that it could be due to uneven lighting inside the LCD monitor.

[John R Smith]

I suppose another aspect of this is that it could be due to uneven lighting inside the LCD monitor.

I think the penny just dropped. I work solely in B/W, so I am very aware of the uneven backlight on my panel. An image in the top LH corner always looks darker than one in the RH lower corner, and so on. Probably a high-end Eizo or similar would fix this.

John

[Ellis Vener]

What was the lighting source in the original photographs? If fluorescent, mercury-vapor or similar  you could have taken the two photos at different points in their phase cycle and then will really deliver two very different color renderings.