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08-16-2010, 07:32 AM   #1
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K7 built-in flash in M

Hi,
Is there a way to fire built-in flash on K-7 with the shutr. speed set >180?
I tried it in M but every time it forced the speed to 180.
Sorry if I missed any threads covering this topic.
Thank you very much,

08-16-2010, 07:36 AM   #2
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QuoteOriginally posted by sinus007 Quote
Hi,
Is there a way to fire built-in flash on K-7 with the shutr. speed set >180?
I tried it in M but every time it forced the speed to 180.
Sorry if I missed any threads covering this topic.
Thank you very much,
1/180 is the top speed on the K7 (and other pentax DSLRs) with the built in flash.

08-16-2010, 10:43 AM   #3
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Jeff,
Thanks for the prompt reply.
Yes, I know that 1/180 is the top speed. I thought I can dial any speed similar to when I use an external flash.
08-16-2010, 11:04 AM   #4
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QuoteOriginally posted by sinus007 Quote
Jeff,
Thanks for the prompt reply.
Yes, I know that 1/180 is the top speed. I thought I can dial any speed similar to when I use an external flash.
You can not dial in a speed over 1/180 as the on board flash does not support HSS. n external flash will only support higher than 1/180 shutter speed when it is in HSS mode, assuming it has one.

Thank you
Russell

08-16-2010, 11:07 AM   #5
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The internal flash does not support HSS - unforunately.
08-16-2010, 12:51 PM   #6
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QuoteOriginally posted by sinus007 Quote
Jeff,
Thanks for the prompt reply.
Yes, I know that 1/180 is the top speed. I thought I can dial any speed similar to when I use an external flash.
As noted, no you can't. Don't know Why we cannot. Doesn't seem like it would take much extra effort to make it happen if any. Maybe they just want us to keep chasing the accessories...

08-16-2010, 01:06 PM   #7
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QuoteOriginally posted by JeffJS Quote
Don't know Why we cannot. Doesn't seem like it would take much extra effort to make it happen if any. Maybe they just want us to keep chasing the accessories...
Considering the multiflash when the on board flash does AF assist, I can't see a reason for the lack of HSS support in it for any reason, but marketing.

Thank you
Russell
08-16-2010, 02:02 PM   #8
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QuoteOriginally posted by JeffJS Quote
As noted, no you can't. Don't know Why we cannot. Doesn't seem like it would take much extra effort to make it happen if any. Maybe they just want us to keep chasing the accessories...
This is a technical limitation due to the type of shutter used. At shutter speeds 1/180th of a second and slower, there is a point where the entire sensor is uncovered at once -- and that's when the flash goes off. But at faster speeds, the exposure is actually created by a slit between the first and second "curtains".

The duration of the flash is usually much shorter than even a fast shutter speed. If a flash is used in this situation, only the portion of the sensor visible when the flash fires would be exposed correctly. The rest would appear dark.

The only solution is to use a different shutter technology (leaf shutters, for example), or to use HSS, which works by firing the flash multiple times in quick succession, imitating the effect of a constant light.

08-16-2010, 02:12 PM   #9
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QuoteOriginally posted by mattdm Quote
This is a technical limitation due to the type of shutter used. At shutter speeds 1/180th of a second and slower, there is a point where the entire sensor is uncovered at once -- and that's when the flash goes off. But at faster speeds, the exposure is actually created by a slit between the first and second "curtains".

The duration of the flash is usually much shorter than even a fast shutter speed. If a flash is used in this situation, only the portion of the sensor visible when the flash fires would be exposed correctly. The rest would appear dark.

The only solution is to use a different shutter technology (leaf shutters, for example), or to use HSS, which works by firing the flash multiple times in quick succession, imitating the effect of a constant light.
I understand all that but I'll ask again. Why can't that be done with the built in flash? In other words, in case that isn't clear, why is HSS not an option from the manufacturer with the built in flash? It's possible with an external flash, why not the built in one?

08-16-2010, 03:32 PM   #10
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QuoteOriginally posted by JeffJS Quote
I understand all that but I'll ask again. Why can't that be done with the built in flash? In other words, in case that isn't clear, why is HSS not an option from the manufacturer with the built in flash? It's possible with an external flash, why not the built in one?
I imagine that it raises the complexity of the control circuitry somewhat, and therefore the expense.

But I think most importantly, using HSS significantly cuts down on flash power. I'm looking at the manual for the Metz 58 AF-1 (because Metz lists this sort of thing), and I see that HSS reduces output by a factor of 5.

That means the output of the built-in flash on that K-7 would go from GN 13 to a very anemic GN 6. That's barely useful.
08-16-2010, 03:53 PM   #11
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I'm sure the 540 and the 360 are reduced as well (effectively). That's kind of what I like about HSS. I have both of the Pentax units so on board HSS isn't really a big concern for me, I just thought I would ask.

I cannot imagine the circuitry being THAT much more complex. P-TTL (supposedly) is already controlling the output based on camera settings (except with M lenses) and subject distance so it doesn't seem like that big of a stretch to put the HSS capability in the on board flash. It isn't something that most (or at least I) use at any great distance. In fact, it's typically rather close up where I use HSS.

08-16-2010, 08:11 PM   #12
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QuoteOriginally posted by JeffJS Quote
I'm sure the 540 and the 360 are reduced as well (effectively).
No question. I just had that manual handy. I just looked at the Pentax one, and they list the decrease too and in fact, even better than Metz does, since they list times for different shutter speeds. At 1/250th of a second, the power decrease is 1/5th (to GN 24.2m at full zoom). And it goes down from there:

Code:
  1/500th = 18.8  (about 1/8th power)
1/1000th = 14 (about 1/15th power)
1/2000th = 10.2 (about 1/28th power)
1/4000th = 7.3 (about 1/55th power)
1/6000th = 6.2 (about 1/76th power)

QuoteOriginally posted by JeffJS Quote
I cannot imagine the circuitry being THAT much more complex. P-TTL (supposedly) is already controlling the output based on camera settings (except with M lenses) and subject distance so it doesn't seem like that big of a stretch to put the HSS capability in the on board flash.
It's got to be able to refresh much more quickly, at least. I won't guess at the details, but I wouldn't be surprised if it's harder than it seems at first glance. Although the earlier models did do that horrible strobing thing for focus assist....

QuoteOriginally posted by JeffJS Quote
It isn't something that most (or at least I) use at any great distance. In fact, it's typically rather close up where I use HSS.
Extrapolating from the above numbers, at 1/500th of a second, the built-in flash would be GN 4.5, and at 1/1000th, GN 3.4. There might be cases where that's useful to provide a tiny bit of fill, but that's very weak.
08-16-2010, 09:42 PM   #13
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QuoteOriginally posted by mattdm Quote
Extrapolating from the above numbers, at 1/500th of a second, the built-in flash would be GN 4.5, and at 1/1000th, GN 3.4. There might be cases where that's useful to provide a tiny bit of fill, but that's very weak.
For my purposes, that's fine. As I said, and I may be alone here, I like to use it for short distances, and by short, I mean a couple feet. This is the type of stuff I might typically use HSS (before I bought the AF160) for..



I can do basically the same thing by stopping the lens way down (the above was at 1/350 f1.9, K10d, FA43mm Ltd) but it doesn't seem to wash over as nicely. Instead I get a lot of unwanted highlights even though a few do exist (hey, it's glazed ceramic). Especially with the on board flash (which I tend to hate anyway). There are probably 100 ways of handling a shot like the above, I just found the HSS at a short distance to work nicely for me.

08-17-2010, 08:01 AM   #14
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QuoteOriginally posted by JeffJS Quote
I understand all that but I'll ask again. Why can't that be done with the built in flash? In other words, in case that isn't clear, why is HSS not an option from the manufacturer with the built in flash? It's possible with an external flash, why not the built in one?

I don't think ANY of the big manufacturers have built-in flashes that support HSS.

I'm guessing it's more complex than you think to implement HSS in the pop-up.

Plus the fact that your GN gets slaughtered when using HSS.
08-17-2010, 08:27 AM   #15
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Hi,
Thanks everyone. Now I understand this thing with on-board flash and HSS.
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