slow speed sync in AV mode?

**Ash** · 11-14-2009, 11:05 PM

Originally posted by Class A

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

Av is an auto mode with the only adjustable factor being aperture - the camera determines the rest. So no, the user doesn't select the shutter speed in Av mode.

Quote:

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.

The manual will not delve into slow-sync speed technique, you'll need to look up a photography reference for that.

As for flash in Av mode setting Tv to 1/FL not making sense, I disagree.
The camera will automatically turn down Tv to permit as much ambient light as possible to expose the image without camera shake becoming an issue. This is precisely where one would want to have such a feature for balanced light photography. It's a gain of over one stop of light in itself from the flash sync speed of 1/180 for lenses around 70mm and less in FL. If this is not a desired effect, the X modes on the K10D and above fix Tv to 1/180. For other models, this can be just as easily done in M mode.

Class A · 11-15-2009, 12:16 AM

Originally posted by Ash

Av is an auto mode with the only adjustable factor being aperture - the camera determines the rest. So no, the user doesn't select the shutter speed in Av mode.

The user obviously cannot directly set the shutter speed in the Av mode, but I can set any shutter speed I like even in Av mode by just selecting the aperture that will result in the shutter speed I want.

In a sense -- leaving flash aside for a moment -- there is no difference for the user whether the camera is in Av or Tv mode. He/She just turns the dial and watches either shutter speed or aperture-ratio and stops whenever the desired value appears. This works for both values because of the reciprocity law.

The difference between Av and Tv comes into play when the lighting is dynamic and changes after settings have been made and the camera then knows which of the two parameters to keep fixed and which to adapt. Without such a dynamic lighting, it doesn't really make sense to say one selects one setting and the other is selected by the camera as both are linked.

I know that the dependent parameter also depends on the ISO setting. This was just to clarify why I regard any parameter to be (indirectly) selectable by the user.

**Ash** · 11-15-2009, 12:35 AM

Originally posted by Class A

The user obviously cannot directly set the shutter speed in the Av mode, but I can set any shutter speed I like even in Av mode by just selecting the aperture that will result in the shutter speed I want.

But that's what Tv mode is for.

Quote:

In a sense -- leaving flash aside for a moment -- there is no difference for the user whether the camera is in Av or Tv mode. He/She just turns the dial and watches either shutter speed or aperture-ratio and stops whenever the desired value appears. This works for both values because of the reciprocity law.

The difference between Av and Tv comes into play when the lighting is dynamic and changes after settings have been made and the camera then knows which of the two parameters to keep fixed and which to adapt. Without such a dynamic lighting, it doesn't really make sense to say one selects one setting and the other is selected by the camera as both are linked.

I know that the dependent parameter also depends on the ISO setting. This was just to clarify why I regard any parameter to be (indirectly) selectable by the user.

Looks like you got the idea.

kittykat46 · 11-15-2009, 02:10 AM

Originally posted by Class A

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.

OK, the camera does increase the shutter speed to adjust exposure vs. ambient if the light is bright , but the point is still that with Flash on in Av mode , Program Mode, Green Mode etc, the camera doesn't care about underexposure vs. ambient.

That's just standard flash exposure logic - Canon and Nikon cameras behave exactly the same way - I've frequently used a Canon 40D and 50D

Originally posted by Class A

So the camera will increase the shutter speed from 1 sec to 1/60, perhaps. That's still slow-speed-sync, or not?

No, that's not slow-speed-sync vs. the technical definition because the camera is compensating against camera shake, not against flash or ambient exposure. If the room is completely dark, or the subject exceeds the flash maximum range, the shutter speed will still be 1/60 secs.

Originally posted by Class A

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?

You just need to understand that normal flash exposure and slow-speed-sync exposure operate on separate and distinctly different rules.

Class A · 11-15-2009, 03:10 AM

Originally posted by kittykat46

...with Flash on in Av mode , Program Mode, Green Mode etc, the camera doesn't care about underexposure vs. ambient.

Yes, and that makes this "flash mode" special, whereas "slow-speed-sync" is just the normal mode of operation.

It previously escaped me that the camera had a special "flash logic mode" when the flash is on and it is set to Av. My flash photography has been minimal so far but I got some radio triggers now and it is good to know that Av mode (on the K100D) has this special behaviour. I would have ended up in M mode most of the time anyway, but still good to know.

Originally posted by kittykat46

You just need to understand that normal flash exposure and slow-speed-sync exposure operate on separate and distinctly different rules.

I think from my later postings it is evident that I understood that by now. It is a bit strange that "slow-speed-sync" is given a special name even tough it is just the normal non-flash behaviour with a flash added into the mix whereas the non-standard (in the sense of deviating from non-flash modes), Av flash logic mode is unnamed.

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11-14-2009, 11:05 PM	#16
Ash Loyal Site Supporter Join Date: Mar 2007 Location: Toowoomba, Queensland Photos: Gallery \| Albums Posts: 23,920	Originally posted by Class A However, the definition seems a bit odd since one could argue that by selecting an aperture the user also selects a shutter speed. Av is an auto mode with the only adjustable factor being aperture - the camera determines the rest. So no, the user doesn't select the shutter speed in Av mode. Quote: 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. The manual will not delve into slow-sync speed technique, you'll need to look up a photography reference for that. As for flash in Av mode setting Tv to 1/FL not making sense, I disagree. The camera will automatically turn down Tv to permit as much ambient light as possible to expose the image without camera shake becoming an issue. This is precisely where one would want to have such a feature for balanced light photography. It's a gain of over one stop of light in itself from the flash sync speed of 1/180 for lenses around 70mm and less in FL. If this is not a desired effect, the X modes on the K10D and above fix Tv to 1/180. For other models, this can be just as easily done in M mode.

11-15-2009, 12:16 AM	#17
Class A Pentaxian Join Date: Aug 2008 Location: Wellington, New Zealand Posts: 11,251	Originally posted by Ash Av is an auto mode with the only adjustable factor being aperture - the camera determines the rest. So no, the user doesn't select the shutter speed in Av mode. The user obviously cannot directly set the shutter speed in the Av mode, but I can set any shutter speed I like even in Av mode by just selecting the aperture that will result in the shutter speed I want. In a sense -- leaving flash aside for a moment -- there is no difference for the user whether the camera is in Av or Tv mode. He/She just turns the dial and watches either shutter speed or aperture-ratio and stops whenever the desired value appears. This works for both values because of the reciprocity law. The difference between Av and Tv comes into play when the lighting is dynamic and changes after settings have been made and the camera then knows which of the two parameters to keep fixed and which to adapt. Without such a dynamic lighting, it doesn't really make sense to say one selects one setting and the other is selected by the camera as both are linked. I know that the dependent parameter also depends on the ISO setting. This was just to clarify why I regard any parameter to be (indirectly) selectable by the user.

11-15-2009, 12:35 AM	#18
Ash Loyal Site Supporter Join Date: Mar 2007 Location: Toowoomba, Queensland Photos: Gallery \| Albums Posts: 23,920	Originally posted by Class A The user obviously cannot directly set the shutter speed in the Av mode, but I can set any shutter speed I like even in Av mode by just selecting the aperture that will result in the shutter speed I want. But that's what Tv mode is for. Quote: In a sense -- leaving flash aside for a moment -- there is no difference for the user whether the camera is in Av or Tv mode. He/She just turns the dial and watches either shutter speed or aperture-ratio and stops whenever the desired value appears. This works for both values because of the reciprocity law. The difference between Av and Tv comes into play when the lighting is dynamic and changes after settings have been made and the camera then knows which of the two parameters to keep fixed and which to adapt. Without such a dynamic lighting, it doesn't really make sense to say one selects one setting and the other is selected by the camera as both are linked. I know that the dependent parameter also depends on the ISO setting. This was just to clarify why I regard any parameter to be (indirectly) selectable by the user. Looks like you got the idea.

11-15-2009, 02:10 AM	#19
kittykat46 Veteran Member Join Date: Dec 2007 Posts: 923	Originally posted by Class A 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. OK, the camera does increase the shutter speed to adjust exposure vs. ambient if the light is bright , but the point is still that with Flash on in Av mode , Program Mode, Green Mode etc, the camera doesn't care about underexposure vs. ambient. That's just standard flash exposure logic - Canon and Nikon cameras behave exactly the same way - I've frequently used a Canon 40D and 50D Originally posted by Class A So the camera will increase the shutter speed from 1 sec to 1/60, perhaps. That's still slow-speed-sync, or not? No, that's not slow-speed-sync vs. the technical definition because the camera is compensating against camera shake, not against flash or ambient exposure. If the room is completely dark, or the subject exceeds the flash maximum range, the shutter speed will still be 1/60 secs. Originally posted by Class A 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? You just need to understand that normal flash exposure and slow-speed-sync exposure operate on separate and distinctly different rules.

11-15-2009, 03:10 AM	#20
Class A Pentaxian Join Date: Aug 2008 Location: Wellington, New Zealand Posts: 11,251	Originally posted by kittykat46 ...with Flash on in Av mode , Program Mode, Green Mode etc, the camera doesn't care about underexposure vs. ambient. Yes, and that makes this "flash mode" special, whereas "slow-speed-sync" is just the normal mode of operation. It previously escaped me that the camera had a special "flash logic mode" when the flash is on and it is set to Av. My flash photography has been minimal so far but I got some radio triggers now and it is good to know that Av mode (on the K100D) has this special behaviour. I would have ended up in M mode most of the time anyway, but still good to know. Originally posted by kittykat46 You just need to understand that normal flash exposure and slow-speed-sync exposure operate on separate and distinctly different rules. I think from my later postings it is evident that I understood that by now. It is a bit strange that "slow-speed-sync" is given a special name even tough it is just the normal non-flash behaviour with a flash added into the mix whereas the non-standard (in the sense of deviating from non-flash modes), Av flash logic mode is unnamed.