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05-14-2014, 12:39 AM   #1
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Metering with M mode using onboard flash

I have a K-30 and a Metz 52, which is a great flash by the way, but I think the problem I get is universal among all cameras and not just my K-30. I shoot manual 99.99% of the time and when I meter with flash onboard, I press the green button to meter and it naturally shows underexpose to the maximum. When I take the pic, it in many cases will slightly overexpose with the first attempt and I need to adjust in my shutter or aperture. Problem is that it is to the max showing to underexpose on the meter but since it is already showing max, I need to reduce in my head by number of stops to reduce to get the correct exposure since the VF meter is already maxed out. It would be better in my mind to show it as in the middle of the exposure bar based on green button metering and I would be able to see how many stops I can see to reduce. I usually just change to AV which is fairly accurate but was just curious on how others are doing in flash when metering in M mode.

05-14-2014, 12:59 AM   #2
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Shutter speed don't have any effect on your flash exposure. It only control your ambient light. If your aperture is at 5.6, be at a 8 feet distance at full power no matter what is your shutter speed. By changing the aperture or distance change the other parameter accordingly. I always get a perfect exposure each time using this technique.
05-14-2014, 02:25 AM   #3
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In manual mode the onboard always fires at full power. You need to either use a hand held flash meter or use the Guide Number to determine the aperture to use. The GN for the K-30 built-in flash at ISO 100 is 12 meters (39.4 feet). Just divide the GN by the flash to subject distance to get the f-stop. So if the distance was 3 meters the f-stop to use would be f4 (12 / 3 = 4).

Using the onboard flash for fill is difficult in manual mode as it always fires at full power. You have to adjust the flash to subject distance or scrim or filter the flash to reduce the amount of light from the flash.

Guide number - Wikipedia, the free encyclopedia
05-14-2014, 03:00 AM   #4
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QuoteOriginally posted by Not a Number Quote
In manual mode the onboard always fires at full power. You need to either use a hand held flash meter or use the Guide Number to determine the aperture to use. The GN for the K-30 built-in flash at ISO 100 is 12 meters (39.4 feet). Just divide the GN by the flash to subject distance to get the f-stop. So if the distance was 3 meters the f-stop to use would be f4 (12 / 3 = 4).

Using the onboard flash for fill is difficult in manual mode as it always fires at full power. You have to adjust the flash to subject distance or scrim or filter the flash to reduce the amount of light from the flash.

Guide number - Wikipedia, the free encyclopedia
We need clarity here rom the OP. In manual flash mode yes, the flash fires at the power it is set at, but in manual exposure mode, but the flash in P-TTL mode, the flash meters correctly, it is just you are in control of the aperture and shutter

Let's find out the case first. Also, I like to use flash in Spot metering mode and concentrate on the subject, otherwise, with varying background distance the meter can take the background and this will overexposed the subject simply because exposure is a function of distance

05-14-2014, 03:43 AM   #5
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Thank you and I understand what you are both saying. I know that I can adjust aperture and shutter speed accordingly to get the exposure I am looking for but what I am wondering if it is similar to what occurs without flash in M mode when you meter with the green button to determine the proper AV/TV exposure just as you get centered without flash in M. I assume that is not possible as I do not see a pre-flash for P-TTL corrections in M mode as I do in AV mode. In AV mode, it is quite easy to do. In M mode, it is more or less not really useful in metering since. An example, I am in M with the Metz 52, I choose metering with the green button, I choose ISO 100, the calculation from metering shows that I should have 1/25 shutter at F2.8 and the camera meter shows it to be 5 stops underexposed. When I shot the camera., the shot was severely overexposed. Now I can adjust the settings to get proper exposure, I think I went to F4 at 1/60 and it worked fine, but when looking at the meter in the VF, to get dead center correct exposure, it shows me that I should be at 1.6" (1/6 Seconds) at F2.8. Now the exposure was not too bad but of course 1.6 seconds would have to be on a tripod. I guess it means that using metering is not ideal in this condition and I need to choose the settings myself in M mode.
05-14-2014, 07:21 AM   #6
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Get a Pentax AF280T flash (generally less than $35 USD). It will provide auto-thyristor flash control and a fair amount of automation on the camera. Surprisingly, the new Pentax bodies support the 30 year-old analog Pentax flash protocols. See my comment on another thread for the full rundown:

https://www.pentaxforums.com/forums/8-pentax-film-slr-discussion/260999-me-su...ml#post2808572


Steve
05-14-2014, 07:41 AM   #7
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Yes, I know it is fairly easy to set the exposure in M mode, it is just not as automatic as non flash metering in the green button. I can set exposure based on knowledge, it is just wondering if there is a way to give an actual meter within manual in flash mode.
05-14-2014, 12:39 PM   #8
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QuoteOriginally posted by JimC1101 Quote
just wondering if there is a way to give an actual meter within manual in flash mode
P-TTL should work in M mode when using a lens having the "A" contacts. With the same lenses, M mode metering should work nicely with the flash though 1/180s will be the highest shutter speed available unless using HSS with an AF lens. Use the meter bar instead of the green button to determine the base exposure.


Steve


Last edited by stevebrot; 05-14-2014 at 12:51 PM.
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