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01-26-2011, 12:44 PM   #16
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So do these numbers only pertain to shooting in Manual mode on both camera and flash or is the 1/160 a limit on the pttl as well. When I think of the pttl I think in terms of auto mode. But again...this could be another one of my problems

01-26-2011, 12:49 PM   #17
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Hey, I have some manuals. Never thought to look there.

AF 200T - 1/1500 to 1/30000
AF 240FT - 1/2000 to 1/30000
AF 400FTZ - 1/1000 to 1/3000 (possible typo?)

edit: looked up some manuals at the PentaxImaging site:

AF 360FGZ - 1/1200 to 1/20000
AF 500FTZ - 1/2000 to 1/30000

Last edited by Just1MoreDave; 01-26-2011 at 01:43 PM.
01-26-2011, 12:58 PM   #18
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QuoteOriginally posted by Deiberson Quote
So do these numbers only pertain to shooting in Manual mode on both camera and flash or is the 1/160 a limit on the pttl as well. When I think of the pttl I think in terms of auto mode. But again...this could be another one of my problems
these limits, specifically 1/180th of a second sync speed on cameras starting with the K10D, (1/150 previously) is a physical limit of the shutter and the flash.

to get higher sync speed you need a faster flash (shorter durtation than the 1/1200 stated and a faster shutter curtain movement.
01-26-2011, 01:23 PM   #19
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This photo shows how short the flash pulses are (the green numbers, outmost row from 6 to 11 o'clock positions). The flash is a Metz 45CT-1, a fairly powerful unit.



01-26-2011, 02:37 PM   #20
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I might as well try reading the dash board of the shuttle if I'm going to try and decipher that thing.

What is it and what does it do?
01-26-2011, 02:42 PM   #21
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QuoteOriginally posted by Deiberson Quote
I might as well try reading the dash board of the shuttle if I'm going to try and decipher that thing.
Among other things:

Power (pulse duration)
---------------------
Full (1/300 sec)
1/2 (1/1000 sec)
1/4 (1/2500 sec)
1/8 (1/4000 sec)
1/16 (1/8000 sec)
1/32 (1/12000 sec)
1/64 (1/16000 sec)

The other numbers are ISO settings and aperture vs distance.
01-26-2011, 02:54 PM   #22
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I would just like to say that this thread has been a great learning experience. I understood the basics of some of this but the detail provided has been quite useful.

Thanks all! And great question, Deiberson.
01-26-2011, 03:09 PM   #23
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Say you're shooting in a dark environment, with your flash. You set the shutter speed at 1/180, because, when using flash (not in HSS mode), the shutter speed is usually irrelevant. It is usually the flash duration that acts as the shutter. Electronic flash units, either builtin or seperate, seldom have a flash duration longer than 1/1000 second. THis is almost always adequate to freeze most human motion. It won't stop a speeding bullet, but it will stop a running person, or a bicyclist.

Let's further assume that, based on the flash, its guide number and the distance to the subject, the aperture works out to f/8.

Now, the question is; would 1/160 @ f/8 give you any kind of recognizable image WITHOUT USING THE FLASH? If it would give you an image, then even with the flash, you will have "ghost" images on your shot. This is the ambient light effect.

If, on the other hand, you would have to open up to 1/30 at f/2.8 to get a picture using the ambient light, then you probably won't see any ghost images. The difference between the flash exposure and the ambient exposure is just too great. Anything more than about two or three stops difference will usually eliminate ghost images.

This scenario is why some people think Pentax should offer higher synch speeds. In a situation in which the flash is the primary light source, the shutter speed doesn't matter, the flash duration does, so 1/180 is okay. When using flash as fill outdoors, in moderately bright light, the ambient light can often be enough to overpower the flash exposure of 1/180 at f/8.

The shutter speed only becomes important when you're in a mixed light environment, but you want the flash to stop the subject motion. If the flash is your only (or primary) light source, no problem. If ambient light is a significant factor, then the 1/180 limit becomes a problem.

01-26-2011, 03:31 PM - 1 Like   #24
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QuoteOriginally posted by noblepa Quote
...when using flash (not in HSS mode), the shutter speed is usually irrelevant.

If, on the other hand, you would have to open up to 1/30 at f/2.8 to get a picture using the ambient light, then you probably won't see any ghost images. The difference between the flash exposure and the ambient exposure is just too great. Anything more than about two or three stops difference will usually eliminate ghost images...
Here's an illustration of a flash pulse freezing the action of an ME Super shutter curtain. In this photo, the flash was triggered by the ME Super. I set the shutter speed of a K7 very low (1/2 or 1 sec). I hit the shutter release of the K7, then hit the shutter release of the ME. The flash fired during the time the shutter of the K7 was fully opened. I turned off all the light in the room to avoid ghosting.

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