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I noticed in a scan I got back from the lab that one side of the photo is much darker than the other, in a gradient type of way. What reason could this be for? The photo was shot on a Pentax K1000 at a shutter speed of 1/1000th of a second, from behind a car window. It shows in other photos that were taken in the same situation (car window, 1/1000) but it’s most prominent here. What reason is this for and how could I avoid this in the future? A photo of a cell tower. One side of the photo is much darker than the other.

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    \$\begingroup\$ Do you have any photos taken with this camera not from behind a car window? The car window is not flat and possibly has a coating on it which could lead to some variation in transmission. \$\endgroup\$
    – Not_Einstein
    Commented Jan 28 at 12:47
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    \$\begingroup\$ This looks to me most like a polarization effect... did you have a filter on? \$\endgroup\$
    – Steven Kersting
    Commented Jan 28 at 17:38

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The possible reason

In a focal plane shutter at high speeds, the two curtains go across the focal plane close to one another, producing a traveling slit. The width of the slit determines at exposure time.

Since the K1000 shutter has horizontal travel, it could be that the two curtains aren't exactly moving at the same speed, causing a widening or narrowing of the slit as the two curtains go across the focal plane at high speeds. This makes the picture lighter on the side where the slit is wider.

If the picture look a bit under-exposed (the brighter side being correct) that would be a 1st curtain slower than the 2nd (narrowing slit), and if it looks a bit over exposed (darker side correct) that would be the 2nd curtain that is slow (widening slit).

And this would become more visible as you use higher speeds.

How to avoid this

If the above is correct, then either:

  • Have the camera serviced
  • Replace the camera (several millions K1000s have been made, so it isn't a rare camera, how much would be a replacement on eBay)?
  • Avoid fast exposures (which is quite easy on a film camera, given the low sensitivity of film)(or get a ND filter...)
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  • \$\begingroup\$ Do you have any suggestions for the OP as to what the remedy might be? Service? Simply avoid such fast shutter speeds? \$\endgroup\$
    – osullic
    Commented Jan 28 at 9:59
  • \$\begingroup\$ Service? How much is a K1000 on eBay, they have sold millions.. \$\endgroup\$
    – xenoid
    Commented Jan 28 at 10:19
  • \$\begingroup\$ Yes, I just think your answer would be improved. You describe the problem. Now just need a little bit about the remedy too. \$\endgroup\$
    – osullic
    Commented Jan 28 at 16:11
  • \$\begingroup\$ I just checked the colors on the two sides of the photo and it turns out the lighter side is more blue than the other, so it’s probably because of the blue tinted part of the window that comes with most windows by default. Thank you for answering! \$\endgroup\$
    – Liamshenko
    Commented Jan 28 at 19:41
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My guess is the car windows were tinted with a polarized window film.

Because the sky is rendered similar to how a polarizing filter might render a sky if the polarizing filter was held at an angle to the plane of the lens.

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