[SEL] Various answers -see message body!

[Larry Evans]

Jerry,

If the camera has a focal plane shutter it can cause some interesting 
effects when taking pictures of moving things.

Regards,
Larry



>This next answer is about Rick's sawblade appearing to cut into it's chassis:
>"Galloway sawblade clearance"
>
>Rick wrote:
>"No Dave that was just a photo fluke that I can't explain."
>&
>Tom, I doubt if I'll ever know what happened there..not a double exposure
>as I checked my camera and it's on auto.  I got down and looked up at the
>same angle yesterday and there is quite a reflection in that part of the
>blade.
>Dunno, but it's kewl
>Take Care, Rick
>
>         Rick has that blade got "cooling slots" cut into it. I'm not sure 
> what you
>people call them but these are slots cut from the "gullet" of the teeth
>inwards for an inch or two (depending on the diameter of the blade) and
>often ending with a circular hole. ( I know this is not the best
>description but hope you understand what I mean). There could be 8 or 10 of
>these - again depending on the diameter.
>         If you used ambient light for the pic your shutter speed may have 
> been
>quite slow. I'm wondering if the effect was not caused by this. I'm going
>to battle to explain my theory in writing so just bear with me - it may
>take a while.
>         With a slow shutter speed and the spinning blade it is possible 
> that the
>camera also caught some of the image that was behind the blade, but visible
>through the cooling slots as they sped past. (Wow this is difficult to
>explain). This could also account for the fact that the steel beam appears
>to be "grey" or "burnt" where the blade has appeared to cut into it -
>because it has received less exposure than the rest - it only exposed each
>time a cooling slot let light past. If you look at the circumference of the
>blade you will see a blurred image as the teeth are creating the same
>effect but because there are more of them (or gaps between them) they are
>not as under exposed. Does this make any sense to any of you - I know what
>I mean but not how to explain it :-). ( To answer another question from the
>list - No I was never a teacher - not in this life or any other :-)) but in
>my next life I intend being a cat in a home like mine. ( You gotta love
>cats to understand that one),
>         The lack of shadows as well as the good illumination of the 
> underside of
>the engine and transporter in the pic points to a flash being used so this
>would make my theory even more difficult to explain as an electronic flash
>should freeze most motion (unless your Galloway runs really fast ;-)) . You
>also mention a lot of reflections in that area which may (or may not)
>account for the fact that this only is visible in that area.
>         To try to explain my theory better I have put a pic of the engine 
> on my
>site (sorry Rick - I never asked permission but only this letter will link
>to it) - check it out.
>
><http://www.oldengine.org/members/evans/rickseng.jpg>
>
>         Whatever the answer I do agree with you - it is a KEWL pic - gets 
> the old
>brain cells working overtime.
>Keep well
>Jerry in S.A.
>
>P.S. For those of you who love cats - you gotta see this pic.
><http://www.oldengine.org/members/evans/cats.jpg>
>
>
>
>
>
>
>
>
>Best regards
>Jerry Evans.
>Databak Hard Drive Data Recovery
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>eMail: jerrye at cyberserv.co.za
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>
>
>
>
>
>
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Larry Evans
MailTo:LFEVANS at pacbell.net
http://www.oldengine.org/members/levans/