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03-18-2012, 09:18 AM   #1
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K-x assist beam DIY? :)

I'm not sure if this has been asked before...

but has anybody tried making a light, camera-mountable, DIY "AF assist beam" for their non-AF beam cams (I use the K-x). I found it very inconvenient when the K-x hunts in low-light or bad lighting. While I could buy an external flash with one, I really wish to avoid doing so because I'm saving up for a K-5 or an excellent f2.8 zoom as quickly as possible.

So if anybody has a good idea or a better one than sticking a small flashlight to the camera body, (which I tried once, and yes, it was stupid... and wasn't helpful coz the flashlight kept falling off lol) please suggest! It would be a really big help, thanks!

03-18-2012, 09:34 AM   #2
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How small is small? Keychain flashlights are tiny and you can get them to stick to the camera pretty easily I think (velcro). I haven't tried though.
03-18-2012, 09:36 AM   #3
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You could probably stick an LED flashlight on the hotshoe

Do you know that if you pop up the flash on the K-x, it'll be used to aid AF?

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03-18-2012, 09:38 AM   #4
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QuoteOriginally posted by Adam Quote
You could probably stick an LED flashlight on the hotshoe

Do you know that if you pop up the flash on the K-x, it'll be used to aid AF?
I've tried to use the flash sometimes to do AF assist, but sometimes it just doesn't respond. And yes, I did pop up the flash!

So I don't know if I'm doing something wrong, but a flashlight will never not work!

Although I have to admit, I haven't had any problems with my k-x autofocus in low-light recently. Primes can be trouble, but when I use my zooms and zoom in all the way to a point of contrast, the k-x works quite well.

03-18-2012, 09:39 AM   #5
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QuoteOriginally posted by Adam Quote
Do you know that if you pop up the flash on the K-x, it'll be used to aid AF?
This, +1

Once you attain focus lock, just push the flash back down.
03-18-2012, 09:50 AM   #6
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QuoteOriginally posted by JinDesu Quote
I've tried to use the flash sometimes to do AF assist, but sometimes it just doesn't respond. And yes, I did pop up the flash!

So I don't know if I'm doing something wrong, but a flashlight will never not work!

Although I have to admit, I haven't had any problems with my k-x autofocus in low-light recently. Primes can be trouble, but when I use my zooms and zoom in all the way to a point of contrast, the k-x works quite well.
Huh, on the few occasions that I've used the flash for AF-assist, it's worked perfectly. But like you, I find the K-x low-light AF to be good as long as there's a bit of contrast.
03-18-2012, 10:22 AM   #7
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QuoteOriginally posted by Alizarine Quote
but has anybody tried making a light, camera-mountable, DIY "AF assist beam" for their non-AF beam cams (I use the K-x). I found it very inconvenient when the K-x hunts in low-light or bad lighting.
I have thought along those lines of using a flashlight of some sort mounted/taped to my K-x - even thought in terms of color of light - white, red, yellow etc.

However I discovered the K-x is actually pretty good at low light - and I only have the two most humble kit zooms -
and I shoot regularly in a very dark jazz club, where in some areas the light is so low that it is actually below both the AF and metering limits of my K-x. (lots of examples and discussion in Kx in Use ( 1 2 3 ... Last Page) )

It may seem obvious -
when the K-x hunts it is mostly because there is almost nothing to focus on -
it may not be quite as obvious -
look for something contrasty that may be easier for the camera to focus on.

Let me try to explain -

EXIF attached.
AE metering segments -

this was clearly below both metering and AF limit of the K-x (with 50-200 zoom) - viewfinder lower display flashing.
(Note: the lower segment readings are very suspect - it is obvious to me that the lower part of the picture is NOT brighter.)

He is wearing a hat, mostly head down while playing, therefore face is in the shadows -
almost impossible to focus on the ideal spot - eyes/glasses.

Yet I want to pre-focus, hold
and wait until his raises his head into the light to take the shot -
but I can't try to focus when that happens - as it is momentary -
and I'll have missed the shot.

So what can I focus on? - the temple forming a "corner" between hat/face/hair is nice and contrasty -
despite the low light - that was relatively easy to focus on when he was not moving his head too much while playing.....

another example:

often musicians play off stage - this pic I called Russell's corner as he plays from there so often -
it is very dark there - again definitely below both AF and metering limits of the K-x (viewfinder display flashing)
I try to focus on the bell of his trumpet if he keeps it still enough - or as a last resort - if lit, the sound board.

Lastly ludicrously dark -


Here's the original as-is no PP other than resize and standard sharpening -

EXIF attached - ISO5000, f/3.5, 1/4sec, 18mm

the light level on the person was so low that I/K-x had difficulty focusing - I couldn't even do it manually as the image was too dark in the viewfinder to focus properly - so I had to pick an area to focus on - it was that junction between his outer shirt and the black T-shirt - now that I see the original shot myself - no wonder I could not focus on his face!

Hope that helps

Last edited by UnknownVT; 03-18-2012 at 10:40 AM.
03-18-2012, 11:36 AM   #8
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Read this post.

03-18-2012, 11:54 AM   #9
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i'm working on one right now to use with the k-r i just got. basically it'lll be a $5, 5mw green laser pointer mounted to a mini ball head screwed into the bottom of the camera with a short cable added to relocate the power button to the camera's grip so that i can turn the laser on with my middle finger while focusing. it should eliminate any hunting with low light or low contrast, it'll have a far greater range than my k-r's af assist light or your flash and it should prevent my k-r from front focusing with tungsten lighting. i'm just waiting for the laser pointer i bought on ebay to get here from china.
03-18-2012, 12:04 PM   #10
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Careful with that 5mW laser, that's powerful enough to dazzle for quite some time and possibly cause some damage if it hits someone in the eye.

Last edited by wildweasel; 03-18-2012 at 12:55 PM.
03-18-2012, 12:30 PM   #11
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laser assist dark AF for Pentax

I use a small novelty laser pointer in red. The camera nails the focus everytime. The laser pointer has a number of shapes e.g. a spaceman, a foot and so on that can be projected by rotating a template in front of the lens. The shape of the image spreads out over a few inches and reduces the chances of eye damage from a concentrated spot. The pointer is small enough to stick on top of the camera with the sticky stuff used for posters.
03-18-2012, 01:02 PM   #12
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QuoteOriginally posted by wildweasel Quote
Careful with that mW laser, that's powerful enough to dazzle for quite some time and possibly cause some damage if it hits someone in the eye.
hitting someone right in the eye and dazzling them with a laser pointer is extremely unlikely unless you're actually trying to do it, and even then it's not easy. the k-x's flash-based focus assist on the other hand can dazzle pretty much everyone in front of your camera, every time. and 5mw isn't going to have any long-lasting effect on someone's eyesight unless they stare directly into the beam for a good long while.

also, i don't recommend using red lasers. with most cameras you'll get a bit of front focusing.

Last edited by maltfalc; 03-18-2012 at 01:10 PM.
03-18-2012, 04:38 PM   #13
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QuoteOriginally posted by wildweasel Quote
Careful with that 5mW laser, that's powerful enough to dazzle for quite some time and possibly cause some damage if it hits someone in the eye.
Indeed. In Australia it's illegal to import lasers with an output level >1mW without approval.

Also forget about merely damaging people's eyes, think about all the camera sensors you might damage, possibly even your own if it hits a reflecting surface.

03-18-2012, 07:03 PM   #14
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You can mount a hotshoe flash like a Metz 50 af1 and use it only in 'illuminator beam' mode without it flashing,
but by experience the Metz 50's beam isn't very strong. Perhaps another model..
03-18-2012, 08:02 PM   #15
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QuoteOriginally posted by Adam Quote
Do you know that if you pop up the flash on the K-x, it'll be used to aid AF?
QuoteOriginally posted by JinDesu Quote
Keychain flashlights are tiny and you can get them to stick to the camera pretty easily I think (velcro). I haven't tried though.
The stroboscopic pulsing of the pop up flash is startling to most people so I don't use it... but good call on LED flashlights. I'll check if there are tiny but powerful ones in the malls here.

@UnknownVT, luftluss

Thanks for those tips! I'll try them next time, though the hard part is trying to find that contrasty spot in 2 seconds tops

@laser suggestions

It seems a great beam assist but I'm not sure if it's OK for use in my country. 5mW is a bit powerful... but wait, lasers can kill sensors? ok I get the last part now.. seems safe for people as long as I don't try dazzling anyone with it.

Last edited by Alizarine; 03-20-2012 at 03:10 AM.
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