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11-14-2009, 11:10 AM   #1
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slow speed sync in AV mode?

Is that possible to do that? I ususally use AV mode to control the DOF and like use it to shoot party in low light.

After checked the user guide of my camera and did some practice, I found can only do the slow speed sync (drag the shutter) in TV mode. My question why it does not allow me do slow speed sync in AV mode? That will be much more convinient to control.

11-14-2009, 11:21 AM   #2
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Try M mode.
11-14-2009, 12:13 PM   #3
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The camera wouldn't know how much you want to drag the shutter in Av mode, so either Tv mode or M mode would be needed.

Come to think of it, TAv mode may be an option too, where you can set shutter speed AND aperture, and the camera does the rest - perhaps try that (don't know myself, but I'll try it next time just to see if it works...)
11-14-2009, 12:24 PM   #4
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QuoteOriginally posted by Ash Quote
The camera wouldn't know how much you want to drag the shutter in Av mode, so either Tv mode or M mode would be needed.
I will use aperture to control the shutter then.

QuoteOriginally posted by Ash Quote
Come to think of it, TAv mode may be an option too, where you can set shutter speed AND aperture, and the camera does the rest - perhaps try that (don't know myself, but I'll try it next time just to see if it works...)
I don't have TAv mode in k100d ...

11-14-2009, 12:36 PM   #5
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QuoteOriginally posted by quaker Quote
Is that possible to do that? I ususally use AV mode to control the DOF and like use it to shoot party in low light.

After checked the user guide of my camera and did some practice, I found can only do the slow speed sync (drag the shutter) in TV mode. My question why it does not allow me do slow speed sync in AV mode? That will be much more convinient to control.
Sorry, but you are asking an impossibility from your electronics. You must set your own shutter speed when using slow speed sync, because the camera has no way of knowing how slow you want to go. You can do this in M and Tv modes. When you are in Av mode, you are asking the camera to set the shutter speed for you to match the aperture you have chosen without flash.
11-14-2009, 12:48 PM   #6
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11-14-2009, 02:33 PM   #7
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Sorry, I don't understand. See, if the flash is not on, both TV and AV will give same pair of shutter and aperture. For example, in AV mode, I set F/4 and camera give 1/10. Then I switch to TV, I set 1/10, camera will give me F/4. The difference if if I turn on flash, in AV mode the shutter may jump to F/4, 1/60, but in TV mode it will keep the same setting, still F/4 and 1/10.

So the question is in TV mode it do not change the exposure after turn on flash, why not implement it in AV mode? I feel AV mode is easier to control.


QuoteOriginally posted by Canada_Rockies Quote
Sorry, but you are asking an impossibility from your electronics. You must set your own shutter speed when using slow speed sync, because the camera has no way of knowing how slow you want to go. You can do this in M and Tv modes. When you are in Av mode, you are asking the camera to set the shutter speed for you to match the aperture you have chosen without flash.
11-14-2009, 02:58 PM   #8
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slow speed sync

QuoteOriginally posted by quaker Quote
Sorry, I don't understand. See, if the flash is not on, both TV and AV will give same pair of shutter and aperture. For example, in AV mode, I set F/4 and camera give 1/10. Then I switch to TV, I set 1/10, camera will give me F/4. The difference if if I turn on flash, in AV mode the shutter may jump to F/4, 1/60, but in TV mode it will keep the same setting, still F/4 and 1/10.

So the question is in TV mode it do not change the exposure after turn on flash, why not implement it in AV mode? I feel AV mode is easier to control.
This is a regular repeated question.

In Av your camera will pick a shutter speed related to the 1/focal-length rule. So a 50mm lens will result in something of about at least 1/75s on my K10 (if I remember correctly, I'll have to check). This is changed on the K-X, because my FA77 now gives 1/50s on my K-X, when I raise the flash. When you zoom you can probably see the shutterspeed change. You must tell the camera that you have no problem with a slower shutter speed, by selecting a special flash mode, named daylight sync or slow-speed sync. I'm not sure if it's available on the k100 and how it is labeled, but it is on eg the K10 or K-X. On the K-X it is in the flash modes and labeled "Slow".

When I select it the camera picks 1/4s at ISO 800 instead of the 1/50s in the dark room I am in. Slow speed sync in Av or P-mode is most useful if you have still relative high light levels, eg during daytime in house or at twilight. When it is really dark than it is better to pick a speed/aperture/ISO in manual, so that you'll have no motion blur (eg 1/60s) and if possible still some ambient lights.

11-14-2009, 03:11 PM   #9
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I'm with the OP on this one.

The camera knows everything it needs to know at the moment the shutter is released. It doesn't matter whether the aperture value comes from a human (M or Tv mode) or is calculated by the camera (Av mode).

I could understand the logic behind enabling slow-speed-sync in M mode only as one uses the aperture to control the flash exposure and the shutter time to control the ambient exposure and neither should affect the other.

Enabling slow-speed-sync in Tv makes as little sense as it would in Av since any control of the ambient exposure will affect the flash exposure.

So the real question does not seem to be "why is it disabled in Av?" but "why is it enabled in Tv?".
11-14-2009, 03:39 PM   #10
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Thanks! your answer is very helpful for me.

No, I only see manual and manual/redeye mode under AV. I understand now, in AV the camera want to assure the picture is not blur so it pickup the secure shutter when flash is on. In TV, the camera understand I will take care of the shutter for myself, so it just don't want to disturb me. :-)

Too bad that k100d doesn't have a slow flash mode under AV. Time to upgrade the body maybe.

QuoteOriginally posted by tomtor Quote
This is a regular repeated question.

In Av your camera will pick a shutter speed related to the 1/focal-length rule. So a 50mm lens will result in something of about at least 1/75s on my K10 (if I remember correctly, I'll have to check). This is changed on the K-X, because my FA77 now gives 1/50s on my K-X, when I raise the flash. When you zoom you can probably see the shutterspeed change. You must tell the camera that you have no problem with a slower shutter speed, by selecting a special flash mode, named daylight sync or slow-speed sync. I'm not sure if it's available on the k100 and how it is labeled, but it is on eg the K10 or K-X. On the K-X it is in the flash modes and labeled "Slow".

When I select it the camera picks 1/4s at ISO 800 instead of the 1/50s in the dark room I am in. Slow speed sync in Av or P-mode is most useful if you have still relative high light levels, eg during daytime in house or at twilight. When it is really dark than it is better to pick a speed/aperture/ISO in manual, so that you'll have no motion blur (eg 1/60s) and if possible still some ambient lights.

Last edited by quaker; 11-14-2009 at 03:49 PM.
11-14-2009, 07:12 PM   #11
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QuoteOriginally posted by Class A Quote
I'm with the OP on this one.

The camera knows everything it needs to know at the moment the shutter is released. It doesn't matter whether the aperture value comes from a human (M or Tv mode) or is calculated by the camera (Av mode).

I could understand the logic behind enabling slow-speed-sync in M mode only as one uses the aperture to control the flash exposure and the shutter time to control the ambient exposure and neither should affect the other.

Enabling slow-speed-sync in Tv makes as little sense as it would in Av since any control of the ambient exposure will affect the flash exposure.

So the real question does not seem to be "why is it disabled in Av?" but "why is it enabled in Tv?".
The point you are missing, and it is easy to miss, is that the camera knows you have turned the flash on. It will increase the shutter speed at that point, because you have more light (from the flash) when you are in Av mode. In Tv and M, it cannot, because those two specific modes tell your camera that YOU want to set the shutter speed. .
11-14-2009, 08:05 PM   #12
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QuoteOriginally posted by Class A Quote
Enabling slow-speed-sync in Tv makes as little sense as it would in Av since any control of the ambient exposure will affect the flash exposure.

So the real question does not seem to be "why is it disabled in Av?" but "why is it enabled in Tv?".
The K100D had no separate slow-speed-sync in the menu, and it has one control wheel.
In Av mode, the control wheel controls the aperture.
With the flash on, the shutter speed defaults to a fixed speed governed by the focal length - and stays there. That's normal flash logic.
Below the 1/180 sync-speed, shutter speed has zero effect on flash exposure, because the flash illuminates for just a fraction of the time the shutter is open.

To provide slow-shutter-sync, they had to put the function somewhere other than Av. So Tv and M it is.
11-14-2009, 08:55 PM   #13
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QuoteOriginally posted by kittykat46 Quote
In Av mode, the control wheel controls the aperture.
With the flash on, the shutter speed defaults to a fixed speed governed by the focal length - and stays there.
It doesn't on my K100D.
While the minimum shutter speed changes with the focal length, the shutter speed chosen by the camera ranges between that minimal shutter speed and 1/180 depending on ambient light.


QuoteOriginally posted by Canada_Rockies Quote
The point you are missing, and it is easy to miss, is that the camera knows you have turned the flash on. It will increase the shutter speed at that point, because you have more light (from the flash) when you are in Av mode.
So the camera will increase the shutter speed from 1 sec to 1/60, perhaps. That's still slow-speed-sync, or not?

Because of the insignificance of the shutter speed for flash exposure, in Tv mode, one is setting the ambient exposure only and asks the camera to match the flash exposure to that. In Av mode, one would be setting the flash exposure only and would be asking the camera to match the ambient exposure. I don't see why one mode (Tv) would make sense, while the other does not (Av).

What am I missing?

Last edited by Class A; 11-14-2009 at 09:02 PM.
11-14-2009, 09:50 PM   #14
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QuoteOriginally posted by Class A Quote
So the camera will increase the shutter speed from 1 sec to 1/60, perhaps. That's still slow-speed-sync, or not?

Because of the insignificance of the shutter speed for flash exposure, in Tv mode, one is setting the ambient exposure only and asks the camera to match the flash exposure to that. In Av mode, one would be setting the flash exposure only and would be asking the camera to match the ambient exposure. I don't see why one mode (Tv) would make sense, while the other does not (Av).

What am I missing?
Not quite. The shutter speed drops to 1/60 as the camera's slowest acceptable shutter speed to avoid camera shake, so although it's slower than flash sync speed, it's not user determined and is not considered slow sync speed.

If I'm keen to use 'slow sync' as determined by 1/FL by the camera in Av mode, I meter ambient light first (without the flash) to determine what ISO I need to get ambient light recording at 1/60, then switch the flas on at those settings and fire away. Otherwise I would use M or TAv modes.

Slow sync on Av means the camera would have to permit the adjustment of shutter speed, which would defeat the purpose of Av mode. Any manually-overridden Tv settings would need a mode that permits that kind of adjustment, which isn't Av mode - unless I'm missing something...
11-14-2009, 10:10 PM   #15
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QuoteOriginally posted by Ash Quote
Not quite. The shutter speed drops to 1/60 as the camera's slowest acceptable shutter speed to avoid camera shake, so although it's slower than flash sync speed, it's not user determined and is not considered slow sync speed.
If the definition of "slow-speed-sync" is that the shutter speed is (only) user-determined then obviously the Av mode doesn't qualify.

However, the definition seems a bit odd since one could argue that by selecting an aperture the user also selects a shutter speed.

On my K100D the shutter speed is not only influenced by an 1/FL rule, even if the flash is up, so the shutter speed is indirectly user selected.

Coming to think of it, it doesn't really make sense for the camera to adjust the shutter speed when it knows the flash will be fired since the shutter speed will have no effect on the flash exposure. Or is the idea to choose a faster shutter speed not to compensate for more light, but to avoid blur overimposed by ambient light exposure? If the latter is true, then Av mode would disqualify as a "slow-speed-sync" mode on the basis that its purpose is to yield images whose exposure is solely determined by the flash in order to provide motion blur images.

I'm not trying to prove "I'm right", just trying to understand. Unfortunately, the K100D manual is very sparse regarding such topics.

My current understanding is that "slow-speed-sync" means that one can choose a shutter speed that the camera would otherwise consider to be unsafe for the purpose of taking blur-free images. The K100D has no extra "slow-speed-sync" setting so in Av it is not possible to override that automatic camera behaviour. I wasn't aware that the K100D applied such automation when in flash mode.

Last edited by Class A; 11-14-2009 at 11:08 PM.
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