March 30, 2011

Your camera lies to you

Filed under: 20-minute,photography — Mark Dalrymple @ 1:57 pm
Tags: ,

A friend dropped me an email yesterday, asking “is there anything you can do with these photos?”.  Here is one of them:


Doesn’t look too bad, does it?  When you zoom in on it, it becomes a disaster:


Out of focus, and terribly noisy.

The image was shot with 12 MP point and shoot, f/5.something at 1/30th, ISO 1600.  Knowing how tiny the sensors are in point and shoot cameras, and therefore how tiny the image wells are for collecting light, I’m amazed that this shot is as good as it is.

Other shots  from the same event had similar problems.  One had the speaker totally out of focus while the audience was in focus.  But it was obvious that wasn’t the photographer’s intent.  So what happened?  Upon further quizzing, the photographer (who otherwise is an excellent DSLR shooter) said that things looked great on the LCD screen.

Camera screens lie to you.  Lying liars lying about lying.

There’s two things to remember when chimping your photos on the camera screen.  The first is that the image being shown is a reduced version.  The camera is downsampling a 12+ MP image into a small, maybe 1 MP screen.  Drastic image reduction makes images look sharper.

The second is you’re looking at a back-lit screen. This photo was obviously taken in a dark environment, so the bright backlight makes the shot look even better.  So it is really easy to understand what happened: a poor shot was made to look ten times better due to the reduction and backlight.

If you chimp (and I am a proud chimper), you should learn how to zoom in on photos to actual pixels at 100%, and a step out, at 50%.  This lets you accurately judge focus and overall sharpness.  On my Nikon DSLRs, I twiddle the menu settings so I can press the button on the multi-selector thumbpad dealie to zoom in to 100%.  I can shoot, chimp, button, check focus, and then move on.

The histogram can be your friend, especially with one of these “shooting in a dark environment” scenarios.  The backlight will make everything look great, even if your image is a stop or two underexposed.  Take a quick peek at the histogram to make sure you don’t have a lot of leftover headroom.

What could have been done to make this particular shoot a success?  A couple of things:

  • Use mechanical stabilization.  Even though the P&S had in-camera image stabilization, the shot was still blurry.  1/30th is hard to hand-hold well, and slower speeds even harder.  I would have tried to brace the camera on a table, chair, building support column, or something.
  • Lower the ISO a stop or two to gain image quality. This will put your shutter speeds into really slow range, but take enough and you may get one sharp one, especially if the speaker isn’t dancing around like a madman.
  • Use a better camera.  A DSLR, especially something that just drinks in the light like a D3[s] or a 5D would let you shoot at higher ISOs without too much worry about image quality.
  • Use a faster lens.  With a point and shoot you don’t have any choice.  On a DSLR, an f/5.6 lens means you will have to shoot at even higher ISO or a slower shutter speed than if you have an f/2.8 lens.

But if you have a bad image, and need to use it, you need to use it.  I made some adjustments in LightRoom to get this “after” picture:

Medium fixed

I used LightRoom 3’s noise reduction (which is most excellent), turned up the contrast and clarity.  You can see there’s a lot more definition in the speaker’s face, and a lot of the noise is gone.  Plus I healed-out the little white blobby thing.

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