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12-21-2011, 05:18 AM   #1
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Shutter Speed on *istD L2

Hi, does anyone know if the shutter speed becomes automatic with the flash on manual on this camera..

When the flash is up I cannot get the shutter speed any faster than 1/180?? Also if I try to slow the shutter speed down, nothing happens??

Thanks
TJ

12-21-2011, 06:59 AM   #2
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I don't have your camera but you can not use faster shutter speeds than the X sync (without tricks)

The shutter consists of two curtains. One is open and one is closed when you start taking the image. The closed one starts opening and a while later the open one starts closing; you will basically have a window moving over the sensor. The shutter speeds determines the size of that window (high speed -> narrow window).

If the flash fires while that window is narrow (e.g. 1/1000sec), only that part of the sensor will receive the light from the flash. So you need that window to be the size of the sensor or bigger. This is at the X sync speed which is probably 1/180. Slower is also fine; in that case the window will be 'wider' than the sensor.

The way to get faster shutter speeds is something called high speed sync where the flash emits a number of flashes while the window moves over the sensor; not sure if it's supported by your camera.

Slower shutter speeds should be possible but it might depend on the mode that you're using.
12-21-2011, 07:19 AM   #3
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Wow, you once you understand the science it all makes sense. OK, so my other question is this... Once I was resolved to this speed, I picked a different location to shoot from. Now the flash is not adding any light??? And when I slow the shutter speed down it is making minimal difference. New shot is closer than old, and on a Christmas tree. ,, I know this because the histograms are not changing or moving right?? How do I deal with this situation???

Thanks.. That last answer was REALLY helpful!!!

TJ
12-21-2011, 07:17 PM   #4
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I have an *istDL2, if you're using the camera's pop-up flash, you're options are limited to what the cameras internal software will allow. If high speed synch is what you really want, look up the Pentax af360 and af540 (I think I got the model numbers right) and see if they support that feature, I don't know if they do. BTW any camera with a leaf shutter, like most rangefinders will sync at all speeds. I do a lot of flash photography with my *istDL2 using non-dedicated flashes, this gives you a lot of latitude for creativity. I haven't tried this with the pop-up flash, but shooting with a thyristor flash you can shoot at speeds lower than the camera's sync speed. The advantage to using a slower speed with the flash is it will allow more ambient/background light to be recorded in the image. A rule of thumb when using manual flashes: F-stop controls flash exposure, and shutter speed controls how much ambient/background light enters the image. Grab some cheap manual/thyristor flashes off Ebay and go crazy (in a matter of speaking). I personally own and use a Sunpak Auto 30DX for on camera flash and two sunpak 544's with radio triggers for off camera flashes. Before you buy an older flash unit check out the link below it is a list of flashes compiled by brand and model, it will give you an idea as to weather it's trigger voltage is low enough to be safe to use on your digital camera. Good luck and have fun.

Photo Strobe Trigger Voltages

12-21-2011, 11:47 PM   #5
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Can you post a failed sample image? It will help people to help you.

I guess you're trying to take a photo of a christmas tree against a bright background and the tree turns out too dark, and therefore you want to use flash to get it properly exposed. Can you confirm that that is correct?

I'm no flash expert but (partially) know the theory behind it If my assumption above about the scene is correct, I think it's one of the most difficult scenes to flash because you have to 'overpower' the light in the background. And for that you need a powerful flash.

QuoteOriginally posted by tj7933 Quote
Once I was resolved to this speed, I picked a different location to shoot from. Now the flash is not adding any light???
The theory (to my knowledge) is to set the exposure for the background using the sync speed (1/180s) and an aperture that results in correct exposure. Next you use the flash to brighten the subject (tree). This will however result in a narrow aperture (else the background would be overexposed). But a narrow aperture limits the reach of the flash (remember: guide number divided by aperture equals maximum subject distance). Assuming your camera choose f/16 (at 1/180s shutter speed) for the scene, and the guide number of the flash is (around) 13, the reach of the flash will be less than one meter so your tree will barely get any extra light.

Also realize / remember that the duration of the light emitted by the flash is (usually) very short compared to the sync speed; therefore changes in shutter speed will not have an effect on the exposure by the flash and only on the exposure by the ambient light.

As indicated, use a flash with a high guide number; a flash with e.g. a guide number of 52 will give 4 times the reach (about 3 to 4 meters with the above f/16). And HSS will help (if your camera and flash support it) as you can use faster shutter speeds and therefore wider apertures (for the same ambient light) and the latter will increase the reach of the flash.

Hope this (hopefully correct) theory helps in the understanding of the problems. As said, I'm no expert, and I'm also battling with this because I don't practice enough; and I'm using an external flash
12-22-2011, 05:01 PM   #6
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Sorry, I think I missed some pertinent info on your second question. Have you tried shooting without the flash and using a slow shutter speed with a tripod? how is the background? is it brighter than the foreground/tree, if it is then shooting without a flash will probably cause the background to get blown out. If you want to try to shoot without a flash on a tripod I would recommend using the 2sec timer in the function menu, this activates the mirror lock-up and minimizes vibration during the exposure.
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