SLR Lenses: Seeing Ghosts

Roger's 8th Birthday Candles

Roger recently turned 8 years old and, of course, I pulled out the camera to document the event and share it with the family.

This is a shot of Roger getting ready to blow out the candles on the awesome Super Mario birthday cake that his mom made.

But note the weird candle-ghosts hovering just in front of Roger’s face. This was one of about 8 shots in the sequence, and the only one where the candle-ghosts weren’t overwhelming.

It is almost a neat effect here, but not at all desirable.

The shot was taken with the 50mm f/1.4 lens, at f/1.8. This is a completely fantastic lens that I have raved about before.

I was chatting with Duncan— who has about umpteen bazillion times more photo skilz & knowledge than me– and showed him the picture.

His conclusion: classic flare. Bad flare. He shoulda seen the others!

In chatting some more, Duncan dropped a link to this Canon tech note on me.

As it turns out, digital camera sensors are more reflective than film.

Thus, it is quite possible that the relatively intense candle light was reflecting off the sensor, then bouncing about the lens and back to the sensor, thus generating ghosts.

Likely enough that Canon has specifically optimized lens design around minimizing the impact of such internal reflections unique to digital sensors.

Amongst other digital specific optimizations, Canon has been reshaping some of the elements to reduce internal reflections off of the sensor. The technote goes there in more detail.

Now, that might not actually be what is going on here. But it warrants further investigation and comparison. Instead of candles, some high intensity LEDs should do the trick.

Fraser Speirs — another photographer with a much bigger photog-clue-stick than me — suggested that it might be the filter. And, in fact, I do have a relatively cheap, totally flat, filter on the lens. I’ll definitely add ‘filter vs. no-filter’ to the testing criteria.

For lenses, I’ll probably just order another plastic fantastic (cheap, kick ass lens — it turns a rebel into a [large] pocket point and shoot) and I may have access to the 50mm f/1.2 lens.

2 Responses to “SLR Lenses: Seeing Ghosts”

  1. annbb says:

    beautiful photo of a beautiful boy.

  2. Janine says:

    FYI, I told my ex about this picture (he’s a serious amateur photographer) and he confirms it was the filter that did it. He says it’s a little better with an expensive, multi-coated filter; the cheap ones are the worst. But any filter can cause this and he says you can reproduce it easily to prove it.

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