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04-29-2021, 01:45 PM   #1
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Green AF light

Hi,
I have the K-70 for several years now, and the first thing I noticed was the green AF assist light. First I thought it was to fit the grey/green UI and the green rings on the DA lenses. Some time later I read, that green light is less unnatural and scares wild animals less. Well, you don't use AF assist, when you shoot shy animals do you? For some time I laid the matter aside, until I saw that the K-3 III also has a green AF light. Does this have a special rational reason, or is it brand specific (like the white lights on Fuji or orange/red in Sony)?
Thanks
J

04-29-2021, 01:59 PM   #2
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I read once that digital camera sensors are twice as sensitive to green as to other colors. How true it may be as a real factor I am not sure.
04-29-2021, 02:02 PM   #3
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I don't know about animals, but it's less harsh to my eyes. Plus I like that it's different from everyone else.
04-29-2021, 02:04 PM - 1 Like   #4
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QuoteOriginally posted by C_Jones Quote
I read once that digital camera sensors are twice as sensitive to green as to other colors. How true it may be as a real factor I am not sure.
AF assist lighting pre-dates camera sensor focussing by a long way. PDAF is colour blind

04-29-2021, 02:36 PM   #5
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I don't think it really matters what color it is from a technical perspective (except for LV AF maybe, because of the bayer filter on the sensor - does it even work with LV? I've never tried) . The green light does fit to the top lcd screen and the displays of the optical viewfinder though.
04-29-2021, 02:53 PM   #6
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Bright white light to help AF also can cause human subjects to squint or otherwise alter their expression. As for animals or other uses, it can come on even when the distance range renders it ineffective, and not good to have a beacon going when you'd rather be of low profile.
04-29-2021, 03:14 PM   #7
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QuoteOriginally posted by othar Quote
I don't think it really matters what color it is from a technical perspective (except for LV AF maybe, because of the bayer filter on the sensor - does it even work with LV? I've never tried) . The green light does fit to the top lcd screen and the displays of the optical viewfinder though.
Totally agree, after all AF assist lights on flashes are red, the opposite of green. I guess the only function is to brighten the subject, regardless of color. Although if you think about it, the green light is much more pleasant on the receiving end of the light.

04-29-2021, 06:24 PM   #8
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Maybe the green light is cheaper to make?
04-29-2021, 07:09 PM   #9
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I think the green light is less harsh and easier on the subjects' eyes in really low light.
04-29-2021, 07:29 PM   #10
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Red light is usually used in the dark as the human eyes are not as sensitive to that. So you night vision is not affected so much by it.
That is why the night vision mode on Pentax cameras are red.

I think green light is a bit more efficient than red when it comes to AF, but if shooting people in the dark a red focus assist would have been preferred.
04-29-2021, 08:18 PM   #11
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More efficiency as Fogel70 stated since camera sensors peak sensitivity is in the green region as with human eyes. Also, for the same amount of power (battery current) a green emitter produces more light than a red one (in terms of mW output). This could be a secondary reason for the shift to green. One other reason might be that sharpest focus is achieved with green light. There is a slight focus shift with most lenses for red or blue light (achromatic lenses are optimized for green).

My most recent flash also has a green assist light. My K-1 allows its green assist light to be turned off if desired (I shoot dimly lighted church pictures occasionally and a bright green assist light isn't desirable - fortunately, the K-1 focuses great without it). When assist lights started to show up, only red LEDs were available. Now you have many choices and green probably has the fore-listed advantages

Last edited by Bob 256; 04-29-2021 at 08:24 PM.
04-29-2021, 11:05 PM   #12
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QuoteOriginally posted by C_Jones Quote
I read once that digital camera sensors are twice as sensitive to green as to other colors. How true it may be as a real factor I am not sure.
This is true, every pixel has 4 (1R, 2G and 1B subpixel) arranged in the Bayer/X-Trans array. But this should only make a difference when focusing in Live-View.
However, thanks for your reply!

---------- Post added 04-29-21 at 11:06 PM ----------

QuoteOriginally posted by Mooncatt Quote
I don't know about animals, but it's less harsh to my eyes. Plus I like that it's different from everyone else.
True ;-)

---------- Post added 04-29-21 at 11:09 PM ----------

QuoteOriginally posted by pschlute Quote
AF assist lighting pre-dates camera sensor focussing by a long way. PDAF is colour blind
Yeah right. Measures the divergence between two beams of light, doesn't it?

---------- Post added 04-29-21 at 11:11 PM ----------

QuoteOriginally posted by othar Quote
I don't think it really matters what color it is from a technical perspective (except for LV AF maybe, because of the bayer filter on the sensor - does it even work with LV? I've never tried) . The green light does fit to the top lcd screen and the displays of the optical viewfinder though.
It works with Live-View. LV even needs it more, as it isn't as sensitive as the PDAF.

---------- Post added 04-29-21 at 11:14 PM ----------

QuoteOriginally posted by mikesbike Quote
Bright white light to help AF also can cause human subjects to squint or otherwise alter their expression. As for animals or other uses, it can come on even when the distance range renders it ineffective, and not good to have a beacon going when you'd rather be of low profile.
Ok, that makes sense.

---------- Post added 04-29-21 at 11:17 PM ----------

QuoteOriginally posted by Bob 256 Quote
More efficiency as Fogel70 stated since camera sensors peak sensitivity is in the green region as with human eyes. Also, for the same amount of power (battery current) a green emitter produces more light than a red one (in terms of mW output). This could be a secondary reason for the shift to green. One other reason might be that sharpest focus is achieved with green light. There is a slight focus shift with most lenses for red or blue light (achromatic lenses are optimized for green).

My most recent flash also has a green assist light. My K-1 allows its green assist light to be turned off if desired (I shoot dimly lighted church pictures occasionally and a bright green assist light isn't desirable - fortunately, the K-1 focuses great without it). When assist lights started to show up, only red LEDs were available. Now you have many choices and green probably has the fore-listed advantages
Thanks. Yeah. I shot in a church too, and the light turned off in the least convenient moment. I turned it off then, and all went fine.

Last edited by ShutterPro; 04-29-2021 at 11:13 PM. Reason: Responded to the wrong reply...
04-30-2021, 05:30 AM   #13
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QuoteOriginally posted by Bob 256 Quote
fortunately, the K-1 focuses great without it).
My K3 II seems to do quite well too. The first few times in low light, I thought it was either defective or a setting wasn't right because I was in rather low light but it didn't illuminate. Apparently what I consider dark isn't dark to the focusing system. Lol
04-30-2021, 07:23 PM   #14
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QuoteOriginally posted by C_Jones Quote
read once that digital camera sensors are twice as sensitive to green as to other colors. How true it may be as a real factor I am not sure.
Human vision is particularly attuned to green light. Between 500~500nm is where the resolution of the human eye is at its highest*, also Lenses of achromatic design are specifically designed to produce the highest resolution peaks in that particular area of the spectrum. Apochromatic lenses are also designed to achieve resolution equal to the green spectral component.



[Simulated average plot of human visual acuity and light frequency - from WolframAlpha.]
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