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11-05-2014, 05:42 AM   #1
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K-3 M42 lens + built-in flash

Hi to all of you,

I am new to this forum but since a few weeks I now own a Pentax K-3. Everything fine 'til now and I am impressed by the image quality.
However I still have one question concerning the usage of manual M42 lenses.
I followed all the guides and tutorials and can shoot with my manual-only lens without problems - as long as I do not use the built-in flash. The stopped down metering on the K-3 works like a charm (apart from the fact that you set the aperture by hand and focus manually you actually do not notice at all that you are using old glass) but when I try to use the built-in flash (do not own external ones - so could not try if they behave the same) all of a sudden I am left with no settings being set automatically. If I pop up the flash I need to adjust all the settings - aperture, shutter, flash intensity - by myself no automatics are working anymore. Am I doing something wrong or is this the default behavior? If it's default, is there a possibility to change this? I thought if the camera is able to measure the available light without the flash it should be able to calculate the required settings even when using the flash.
Any recommendations how to use my manual-only lens with the flash?

Thanks in advance and have a nice day,
Peter

11-05-2014, 07:57 AM   #2
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There is no automatic flash function with any lens made before the A series.
11-05-2014, 08:23 AM   #3
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QuoteOriginally posted by Kozlok Quote
There is no automatic flash function with any lens made before the A series.
The flash will always fire at full intensity with all lenses lacking the A contacts. This is true even when the flash EV compensation is set to something other than zero. With the built-in flash you are limited to fully manual operation with the aperture determined by distance (guide number distance = aperture). The guide number of the flash is 13 (ISO 100/m). There is a guide number table on page 42 of the user manual for other ISO settings. If you need metered flash to use with your M42 lenses, I would suggest an auto-thyristor flash having a sensor built into the flash itself. I use a Pentax AF280T with my non-A vintage lenses. Although it does not support P-TTL, it does provide a surprising number of dedicated features when used with a current model Pentax bodies. You can also buy an auto-thyristor unit new for less than $100 USD.

http://www.bhphotovideo.com/c/search?atclk=Flash+Type_Auto+%28Non-TTL%29&ci=...822+4062787806


Steve

Last edited by stevebrot; 11-05-2014 at 08:34 AM.
11-05-2014, 08:30 AM   #4
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Yep. Just one more tidbit, if you will buy an older flash, be careful. Many flashes made before the digital era have too high Voltage and can damage your digital camera. So don't use a very old flash, at least not without special tools that block the voltage.

11-05-2014, 08:34 AM   #5
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With non-A type lenses the built-in flash fires at full power. You have to use the Guide Number divided by flash to subject distance to determine the f-stop. The GN for the K-3 is 13 meters at ISO 100.
11-05-2014, 09:11 AM   #6
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QuoteOriginally posted by Na Horuk Quote
Many flashes made before the digital era have too high Voltage and can damage your digital camera.
This is a very important point. I have an 80's vintage Vivitar flash that I have to remember to not mount on the K-3 because it has a very high trigger voltage. The good news is that all Pentax-brand flashes have safe trigger voltage. I would expect the same for any generic flash purchased from a reputable dealer.


Steve
11-05-2014, 11:36 AM   #7
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QuoteOriginally posted by Not a Number Quote
You have to use the Guide Number divided by flash to subject distance to determine the f-stop. The GN for the K-3 is 13 meters at ISO 100
So at 2 meters, you'll be shooting somewhere between 5.6 and 8.

Set your camera on 'M' mode. Set your aperture at the halfway mark between 5.6 and 8. Press the green button to set the shutter speed. The shutter speed must be 1/180th or slower. Pop up the flash and take a test shot, Adjust to taste.

If you're shooting indoors, just set your shutter speed to 1/60 or so as slower speeds will give you camera movement trails. The shutter speed isn't all that important as the flash provides principal exposure.
11-05-2014, 12:01 PM   #8
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Look up the guide number and calculate the required f stop based on it and the distance (and iso).

Oh sorry "Not a Number" said it already.

11-05-2014, 01:04 PM   #9
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QuoteOriginally posted by dms Quote
Oh sorry "Not a Number" said it already.
So did stevebrot
11-06-2014, 08:32 AM   #10
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Thanks all for your remarks, I was not aware of the fact that I should do all this manually. Anyhow, I will get used to it.

Thanks,
Peter
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