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02-22-2016, 02:33 AM   #1
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using fill flash with K-x, M42 lens?

I was planning on a small trip recently to capture some images of local water fowl. It was going to be cloudy, so I decided that I would try setting up the Pentax KX with a fill flash, with the flash being the Yongnuo YN460 II mounted on the hot shoe. I was also going to use my M42 Takumar 200mm f/4 lens. Normally, sunlight brightness is enough that I can set shutter from 1/1500-2500 or so and not have any blurring issues, but cloudy/ rainy days mean maybe 1/500 or so, and that's when I decided to try flash. However, despite everything I tried, I wasn't able to set the shutter any higher than 1/200 to activate flash. If set at 1/1000 for example, no flash. 1/200 would have been overkill with blown highlights even without flash. I guess I could somewhat control exposure by adjusting the aperture ring on the lens and maybe that's how I would have to do it. I suppose that since I'm using a manual M42 lens and basic flash has something to do with my issue. Thanks for any response.

02-22-2016, 03:27 AM   #2
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Max sync speed is 1/180. To use a higher shutter speed you need a p-ttl flash capable of using high speed sync, or you need to cut the ambient with a ND filter in order to shoot at max sync speed. The first solution reduces flash power, the second may require more flash power than a single flash can provide, depending on your exact conditions and requirements. In both cases overcoming ambient light may require getting your flash closer to your subject, which often means getting the flash off camera.
02-22-2016, 03:55 AM   #3
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QuoteOriginally posted by ctron Quote
with the flash being the Yongnuo YN460 II mounted on the hot shoe.
That's your problem.

A genuine Pentax flash like the 360 or 540 will do the 1/2500s you want.
02-22-2016, 10:38 AM   #4
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This high speed flash sync trick is at the expense of greatly reduced flash strength. Will a HSS capable flash have the range needed for the 200mm shot and birds? I guess you can find out.


Last edited by tuco; 02-22-2016 at 01:36 PM. Reason: fix
02-22-2016, 02:31 PM   #5
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QuoteOriginally posted by tuco Quote
This high speed flash sync trick is at the expense of greatly reduced flash strength. Will a HSS capable flash have the range needed for the 200mm shot and birds? I guess you can find out.
You put a Fresnel lens in front for that situation.
02-22-2016, 02:35 PM   #6
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QuoteOriginally posted by clackers Quote
You put a Fresnel lens in front for that situation.
I've seen those in action. But with a strong flash. I have no experience with it and HSS. How far has your HSS flash reached with one of those fresnel lenses on?
02-22-2016, 02:42 PM - 1 Like   #7
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QuoteOriginally posted by tuco Quote
I've seen those in action. But with a strong flash. I have no experience with it and HSS. How far has your HSS flash reached with one of those fresnel lenses on?
Oh, at least 40 metres when playing.

Because light is reduced by inverse square over a distance, that's the major factor, and a Better Beamer or similar acts to keep it parallel for as long as possible.

Last edited by clackers; 02-22-2016 at 07:43 PM.
02-22-2016, 02:49 PM   #8
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QuoteOriginally posted by clackers Quote
Oh, at least 40 metres when playing.

Because light is reduced by inverse square over a distance, that's the major factor, and a Better Beamer or similar acts to keep it parallel fo as long as possible.
Good to know. Thanks.

02-22-2016, 03:48 PM   #9
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Since nobody else said it yet, yes, you should experiment with adjusting the aperture on your lens. It's not your lens, it's the max sync speed for flash on Pentax cameras that's holding back your shutter speed. You can try other means of decreasing your exposure to work with 1/180 shutter speed, but you should be familiar with what you can change by adjusting your aperture if you want to find the best combination for you.

Ignore me if you've already done this, but set ISO to 100 right off the bat if it isn't already (or 80 for those with a K-5). Then set your aperture as high as you can before diffraction starts to hurt the image. You'll have to experiment to find out where it starts going bad by taking a couple shots and zooming in to look at detail, but probably f/11 or so should be acceptable. (Keep in mind this will increase depth of field a bit.) The only other way to decrease ambient exposure after that is to use an ND filter or get a flash capable of high speed sync.

Depending on location, try shooting from an angle that limits the amount of sky in your frame. For example, shoot downhill rather than uphill. This way the background is less sky and more foliage or diffused reflections on water. And if there are only trees on one side of the pond, use that for your background.
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