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Thread: Shadowing at high shutter speeds

  1. #1
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    Default Shadowing at high shutter speeds

    High people. I don't have a decent bird lens yet so this problem is relating to some reptile shots. Any input is much appreciated.
    Attachment 9679
    the following pics were both taken with a nikon D3000 using a Sigma 105mm 1:2.8macro and an old Starblitz 16M mounted flash.
    The first pic was shot at F16, S/speed 1/250 and is fine. In the second pic the S/speed was increased to 1/320 and shadowing occurred. Shadowing occurs at all appertures and only begins after S/speed exceeds 1/250. I have now tried it on an Nikon 18-55 lens and the same occurs, I can only conclude there is not enough light getting through and possibly that the angle or spread of light is not sufficient, Im hoping it is all related to the old flash and not my camera, I don't have access to a more modern Nikon flash to test it out.
    Any thoughts would be appreciated.

    Steve.
    Attached Thumbnails Attached Thumbnails _DSC0149.jpg   _DSC0148.jpg  

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    HI Steve
    I cannot see an attached image. My initial suspicion is that your camera's maximum flash synch speed is 1/250th, which means that any flash that you attach will not fire fast enough over a shutter speed of 1/250th. Your darkness (I imagine bands top or bottom?) are the shutter blades in the camera closing faster than the flash can fire. If you have a dedicated flash unit, you can set high-speed synch thus manage to get the flash to fire as fast as the shutter. I am hoping to see your attached image soon, in case it's not what I am thinking.

    I can see now. awesome shots BTW. Yes, a synch issue. You should not set the shutter faster than 1/250th. I often shoot reptiles close too and use manual exposure, 1/125th and aperture between f/8-16 or so. The flash gives the light when you are this close, so you can slow the shutter down too without compromising sharpness.

    What is this anyway? A legless lizard?

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    Thanks Akos.
    I have had a similar reply on another forum which went along the lines of. The flash and camera not communicating in the same language properly via the hotseat ie: Not dedicated. The flash is maybe 20yo and possibly much older, so yeah not ideal.

    Thanks for the compliment. Yes it's a legless lizard. Granite Worm Lizard, Aprasia pulchella. It is an uncommonly seen species found in granite and laterite soils in the Perth hills.

    Steve

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    Hi Steve,
    Akos is spot on. The issue is simply using a higher shutter speed than the flash sync speed. Different model cameras will have varying flash sync speeds. High Speed Sync is a relatively new function in hotshoe mounted flashes on SLR cameras. Only the newer ones will offer the functionality. Doesn't seem like long ago that even 1/250th was an amazing feat!
    Cheers, Dave

    www.davidstowe.com.au WORKSHOPS - www.flockwildlife.com

    Aus Life List IOC= 688 - Carpentarian Grasswren
    "So God created every winged bird according to its kind. And God saw that it was good." Genesis 1:21


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    So will purchasing a better flash designed for DSLR's fix this? I imagine that a dedicated nikon flash would sync better with the camera, and that possibly newer flashes with current technology would fire more efficiently than my old dinosaur.

    I will try and find out if the flashsync speed is in fact 1/250
    Last edited by Steve1; 09-06-2011 at 09:28 PM.

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    http://www.imaging-resource.com/PRODS/D3000/D3000A.HTM
    FSS is actually 1/200th according to this article. I must admit that i am a canon man so i don't know which Nikon flash units would provide high speed sync. Gerard or another Nikon user should be able to help? But i would assume that "yes", buying a new flash will allow this function and also most likely provide you with a higher guide number (measure of flash output).
    Cheers, Dave

    www.davidstowe.com.au WORKSHOPS - www.flockwildlife.com

    Aus Life List IOC= 688 - Carpentarian Grasswren
    "So God created every winged bird according to its kind. And God saw that it was good." Genesis 1:21


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    Steve, in fact the camera and flash are not communicating at all with an old manual flash all that happens is the camera closes the flash contact at the appropriate time in the exposure and activates the flash which gives out a pre determined light burst.

    What is happening here is that the first shutter curtain has not fully opened before second curtain starts to close. The flash starts when the first curtain is fully open but at a shutter speed above the cameras max sync speed there is no time when the entire frame is exposed while the flash fires. At higher shutter speeds the shutter begins closing (The second curtain starts to close) before the first curtain is fully open so you have a slot of varying height travelling across the frame. At slower speeds the first curtain fully opens, the flash goes off then the second curtain closes. This works because the flash pulse is of very short duration. What you are seeing here is the second curtain shadowing the frame as it has started closing when the flash is triggered by the first curtain opening fully.

    A modern flash brings a lot of advantages, including faster recycle, high speed sync, second curtain sync, E-TTL metering for the flash, automatic fill flash allowing you dial flash exposure compensation to set the fill ratio. It syncs at high shutter speeds by strobing so the flash is illuminated the whole time the slot travels across the frame. Second curtain sync allows natural looking blurs when used at night, the flash going off at the end of the exposure. ETTL flash metering means you can just dial in your fill ratio.

    The downside of high speed sync is lower flash output as it needs to strobe very rapidly to provide illumination across the whole frame without over exposing the frame. Basically flash exposure in controlled by varying the time the flash circuit is activated as the flash itself operates at constant brightness. So for instance to get 50% flash output, the flash cycles on an off very rapidly so that it is powered up 50% of the time and does this the entire time from when the first curtain opens fully till the second curtain closes. When high speed flash is not activated the flash goes off and is very rapidly shut down when enough light has been gathered. At low power this might be open for 1/10,000 of a second or less. Something like the Canon 580EXII is illuminated for 1/800 of a second at full power.

    A couple of inks talking about flash sync:

    http://en.wikipedia.org/wiki/Flash_synchronization

    http://www.photozone.de/hi-speed-flash-sync
    Chris Ross
    Helensburgh NSW
    www.aus-natural.com
    Instagram: @ausnaturalimages

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    Thanks very much Chris. If you don't mind I would like to paste your post in another forum (Reptile) so others may benefit from the information.

    The information you guys have taken the time to post has been great, and while a lot to take in, I understand my camera a lot better for it and it's much appreciated.

    Regards
    Steve

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    Steve,
    Ok if you want to post, though the two links I provided give most of the info you need.
    Chris Ross
    Helensburgh NSW
    www.aus-natural.com
    Instagram: @ausnaturalimages

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    Once again, cheers I have copied your post with the links included.

    Steve

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