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04-13-2010, 01:08 PM   #1
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Using manual mode on 540/360

Hi there,
I've been a Pentax shooter for a few years now but have never been educated on using manual mode on flashes.

I have two external flashes, the AF540 and AF360, and I will be using both of them with wireless triggers to take a large group portrait.
I plan to have each flash on a stand on each side of the camera about 10-15 ft. away.

Because my triggers don't transmit TTL data, I am wondering what setting to adjust the flashes to so that they put out equal amounts of light.
The 540 at 1/4 power will put out more than the 360 at 1/4 right?

Thanks for any advice on this! I would like to get this photograph right.

Oh I'll be using a K-7 most likely with the 16-45mm Pentax lens, or possibly an FA35.

04-13-2010, 02:48 PM   #2
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Why don't you just go wireless control from the K7 and use P-TTL?

04-14-2010, 12:03 AM   #3
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Thanks for the reply.

Two reasons. The first is I prefer not to have any center flash, and the second is it will be outdoors most likely in bright daylight which means the chance of the flashes detecting the onboard K-7 flash is lower.

Should I post this somewhere else?
04-14-2010, 05:57 AM   #4
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I doubt there is a concrete answer anyone can give you on the flash power. you have two different flashes, at different positions. have your assistant stand where the group will stand with a light meter, take a few shots and see what the readings are.

alternately use a third 360 or 540 on camera as the wireless controller (not master), it's a lot more powerful than the on-board flash and should be able to reach the slaves, even in the sunlight. controller mode means that flash will not fire for the actual exposure.

04-14-2010, 11:18 AM   #5
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If you dont want to use TTL wireless then why not use Auto on both flashes and set them to your desired f/stop? That way the 540 will pump out enough light to reach f8 (for example) and the 360 will do the same.

I've tried it in different situations and they work fine.
04-14-2010, 11:30 AM   #6
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Use the Guide Number for each flash, divide by distance to give you aperture. Adjust individual flash power or distance to arrive at desired lighting ratio.
04-14-2010, 02:57 PM   #7
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The AF540 is specified at double the power of the AF360. So if you put the 360 at full power, and the 540 is the same distance and 1/2 power, the flashes would be roughly balanced. Or, Set them both at full power, and move the AF540 40% further away.

I used my nice flash meter to measure full power of my AF540 and my two AF360s, (Along with 4 other older Pentax flashes). They all put out about half their specified power (Marketing spec gimick, since they are all accurate on Auto sensor mode). Also one of the AF360s (the newer one) puts out 50% less power than my older AF360. So, If you use guide numbers, you will not have an accurate exposure; if you adjust your F Stop to compensate for the flashes putting out half what they claim, you'll probably be closer to correct exposure.

I wouldn't recommend setting two flashes in Auto mode, Since they can confuse each other, The first one might give almost all the light, and the second one seeing the first go off, will give very little light.

04-14-2010, 03:12 PM   #8
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That helps a lot, thanks!

Now I understand more about the auto mode and that does coincide with my desire to set them manually.

Running some unscientific experiments before reading your post and with the 540 at half of the rating of the 360 they look very similar, so I'm glad that is how they are spec'd.
Maybe I can round up a couple guinea pigs before hand to test out the exposure before-hand. I am just happy to learn about using the manual mode on these flashes, it's something I avoided before.
04-14-2010, 03:26 PM   #9
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QuoteOriginally posted by rgibbons Quote
The AF540 is specified at double the power of the AF360. So if you put the 360 at full power, and the 540 is the same distance and 1/2 power, the flashes would be roughly balanced. Or, Set them both at full power, and move the AF540 40% further away.

I used my nice flash meter to measure full power of my AF540 and my two AF360s, (Along with 4 other older Pentax flashes). They all put out about half their specified power (Marketing spec gimick, since they are all accurate on Auto sensor mode). Also one of the AF360s (the newer one) puts out 50% less power than my older AF360. So, If you use guide numbers, you will not have an accurate exposure; if you adjust your F Stop to compensate for the flashes putting out half what they claim, you'll probably be closer to correct exposure.

I wouldn't recommend setting two flashes in Auto mode, Since they can confuse each other, The first one might give almost all the light, and the second one seeing the first go off, will give very little light.
Actually, for me, both flashes gave the correct exposure from its AUTO settings but I can see how it can be fooled into not giving enough light thinking that it doesn't need to. Maybe its too situational to be consistent.
But what you describe DOES happen a lot of times when I use wireless PTTL. My main light wont fire because the rim or kicker lights on the other side seem to mess up the metering when they fire. I'm going to get to the bottom of that this weekend.
Your newer 360 isn't as strong as your old one? Interesting. How old is the older one? I have one thats 3 yrs old and one made last year.

To the OP, see how the flash power is for both flashes with different exposures. After a while, you'll get to know how much light will hit your subject at various distances and power levels. If you have a flashmeter all the better. My 540 can go from f22 till 5 ft, f16 till 9 ft and f11 till 15-17 ft (ISO100) zoomed into 85mm. A shoot-thru umbrella cuts 1-1.5 stops of light from that. You may get slightly different results but you'll at least be in the ballpark.
04-16-2010, 07:51 PM   #10
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I have the same flashes, and in my wireless portraiture practice, using them in Manual mode, I kept the power levels the same but have the 540 about a third further away from the subject. Results have been quite consistent.

On the other hand, I did experiment them at equal distances at the same power level on purpose, with the 540 power level dialed to the proper exposure. Results from this experiment have been quite pleasing also especially with one-person portraits where the lighting effects were slightly dramatic and interesting.
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