[LRflex] Re: Focal Plane Shutter Distortion.
- From: "Aram Langhans" <leica_r8@xxxxxxxxxxx>
- To: <leicareflex@xxxxxxxxxxxxx>
- Date: Tue, 2 Feb 2010 11:10:54 -0800
Excellent point. You are correct. Increase my distance by a factor of 2
perhaps.
Aram
--------------------------------------------------
From: "Charlie Falke" <chfalke@xxxxxxx>
Sent: Tuesday, February 02, 2010 11:05 AM
To: <leicareflex@xxxxxxxxxxxxx>
Subject: [LRflex] Re: Focal Plane Shutter Distortion.
> On 2/2/2010 12:56 PM, Aram Langhans wrote:
>> You sparked a curious question in my mind. The retired science teacher
>> part
>> of me came back to life. A bit of math. Traveling at 115 kph, the bike
>> would move about 3 cm in 1/1000 of a second. Since the wheel occupies
>> maybe
>> 1/4 of the vertical frame (vertical shutter) it would move about 0.75 cm
>> during the exposure. I don't think 0.75 cm would make a detectable
>> lengthening of the wheel, do you?
>>
>> This in no way detracts from the great shot, just, in my mind, casts
>> doubt
>> as to the distortion effect seen.
>>
>> Aram
>>
>>
>
> Aram,
> The exposure time isn't the right number to use,
> the shutter transit time is. This is always
> slower than the maximum shutter speed. In the specs
> for a camera the easiest way to find it is the fastest
> shutter speed you can use with electronic flash.
> With horizontal cloth shutters this ranged from 1/25
> for a Barnack Leica, 1/50 for an M, to 1/100 for the SL.
> The vertical Copal Square appearing in the Nikkormat
> raised this to 1/125 and later to 1/250.
> If I believe Rockwell, (syncspeed.htm#speeds
> <http://www.kenrockwell.com/tech/syncspeed.htm#speeds>) DSLRs
> have a transit time of 1/500. This is reasonable since
> the distance they need to cover is smaller and they are
> electric.
> So there may be some distortion, but not a lot. I know
> I can see it in shots of propellers and rotor blades,
> but they move quite fast, and their geometry shows even
> small amounts of distortion.
>
> --
> Charlie Falke _____ /\
> | __/\__/------/__)
> |(____\/_________/
> "One test result is worth | |/ `o
> one thousand expert opinions" - Wernher Von Braun 0 N4003M
> "Imagination is more important than knowledge" - Albert Einstein
>
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