increasing shutter speed with flash

Howdy,

I'm demonstrating just how much of an amateur I am with this question but I'm hoping one of you gurus can help.

How do you increase the sutter speed for the *istD when the pop-up flash is on?

When I engage the flash it overrides the shutter speed and won't "allow" a faster shhutter speed than 150. This is very annoying especially when using trhe flash for macro stuff.

Why does it do this and is there any way to turn it off? I'd love to get really quick shutter speed for insects etc

Thanks

Jimmy

Jimmy,
You can't increase the shutter speed, only slow it down.
The limitation is called the "sync" speed..

With the *ist-D you can use the AF360FGZ external flash to do high speed sync, above 1/150s. Not quite sure how high you can go, but the power of the flash is greatly reduced in this mode - hence it's available as a separate option on the slide switch of the AF360FGZ. You also have various other useful flash modes that are not available on the pop-up.

As far as I am aware, the AF360 is the only flash that supports high speed sync.

What is even more interesting is the AF360 does wireless flash. I took some macro shots of a moth using extension tubes and the SMC-F 100mm/f2.8 macro, and lit it with the AF360 on wireless mode (so I could hold the flash in the right position). Got some great results!

So, unfortunately you can't do it with the pop-up flash, because it doesn't have enough power to run in high speed sync mode.

Matt

Unless you are using a special flashgun, you cannot use a higher speed than 1/150th.

This is because at higher speeds only part of the sensor is exposed to light at any one time, so you would get an image which was partly lit by flash and partly by ambient light.

Some flashguns emit a series of light bursts which ensure that the flash reaches all parts of the sensor, even at higher speeds. If the body recognises one of these guns is attached, and in high-speed mode, it will permit higher speeds to be set.

At the moment only the 360 and the newly anounced gun (550?) amongst the Pentax flashes offer this functionality. I believe one of the Sigma guns does too, and there may be others.

Look for a feature called "HSS" - high speed sync.

G

There's also a feature on this board called SMP - synchronised message posting!

G

thanks for the detailed responses guys. I must admit I thought that might be th case and I actually started looking a external flashes last week.

Looks like I'll have to move a little faster on that

Jimmy

For what it's worth, I found that the Sigma 550 Super (not the ST) offers hi speed sync, wireless etc. It's more expensive than the AF360, but has a higher guide number.

Matt

Hi Matt,

thanks for your feedeback.

I'm still unsure how to overcome the issue of slower shutter speed for macro shots. Even if I use a slave or other external lighting the istD still won't "let" me increase the shutter speed.

Are there fancy menu options that I need to adjust? How do you overcome the default features using external flashes or other lighting?

Thanks

Jimmy

Jimmy,

You cannot increase the shutter speed, unless you have an AF360FGZ which supports High Speed Sync. (There is one Sigma flash that support high speed sync, but it's more expensive than the AF360.)

External slaves, popup flash - all are restricted because the circuit design for high speed sync is different, and you need oodles of power.

Hope that clarifies the matter
Matt