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Re: [OM] More on DOF and focal length (by Ctein)

Subject: Re: [OM] More on DOF and focal length (by Ctein)
From: Fernando Gonzalez Gentile <fgnzalez@xxxxxxxxxxxxx>
Date: Sat, 27 Jun 2009 16:42:55 -0300
Oh well - so Ken doesn't seem to agree with Ctein ... :-(

Yes, I always wondered _why wasn't that line scribed on the outside of 
the body to mark the position of the image plane_ on the OM bodies, and 
it was on C*non bodies I happened to use, like the A1 etc.

Little if any time to play with the 300/4,5 so far. Seems that I'm 
having fun looking at it instead of through it :-)

An interesting 'hearing ability' test: last Tuesday I showed it to my 
daughter, she immediately asked 'What's that noise like sand inside the 
lens?'. Skeptically, I shake (shaked, shoke ?) the lens very close to my 
ear, and I did hear something like little metal pieces crashing, 
dithering. Still don't know if it's the sound of the diaphragm blades, 
or if it's been designed with ball bearings ... otoh, it's amazing how 
soft does it sound when pressing the shutter.

See it here (poor focus, sorry) 
<http://www.flickr.com/photos/fernando_gonzalez_gentile/3659278092/sizes/l/>

If I wasn't about to kill mDNSResponder.exe and mdnsNSP.dll, I would be 
out and taking pictures ... :-(

Fernando

Chuck Norcutt wrote:
> Normally said as "all wet" rather than "completely wet".  At least I 
> think that's what he meant.  See definition #2 here:
> <http://en.wiktionary.org/wiki/all_wet>
>
> That's a pretty fearsome critter you've got there.  I'm glad I'm not 
> only 25mm tall.  :-)
>
> When computing depth of field for macro work you must remember that 
> subject distance is the distance from the image plane and not from the 
> lens.  Some cameras have a line scribed on the outside of the body to 
> mark the position of the image plane... to be used for macro work.  If 
> the subject is 100 meters away the difference between the front of the 
> lens and the image plane is unimportant.
>
> ps:  How's that 300/4.5 working?
>
> Chuck Norcutt
>
> Fernando Gonzalez Gentile wrote:
>   
>> Very interesting .... what d'you mean by 'wet', Ken?
>>
>> Now I realize I should go back to a thread I hardly understood, where I 
>> got lost at the idiomatic use of CoC.
>>
>> Ctein's writing should add another item in his list of validation 
>> criteria: trial and error. (*).
>> Yes, I completely agree with him, and not with the article at 
>> <http://luminous-landscape.com/tutorials/dof2.shtml>.
>> During last year I faced this problem several times, specially in two 
>> situations where the d.o.f. scale marked on the Zuiko could be used no 
>> more: the 21/3,5 + 7mm tube, and the 200/4 + 2X-A ... trial and error, 
>> and d.o.f preview button. The latter, too misleading for the 21+7mm. 
>> Here's a 'trial and error' example of mine, the only one I happened to 
>> scan. Yes I did want its horn to come out in focus, IIRC I estimated it 
>> was at about 10 cm far, and focus plane is oblique.
>>
>> handheld OM 2n on Auto mode, Zuiko 21mmƒ/3,5 at ƒ/16, 7mm extension 
>> tube, 49mm linear polarizer, Provia 100F
>>
>> link to 1280, link to view on black.
>>
>> <http://www.flickr.com/photos/fernando_gonzalez_gentile/2316283298/>
>>
>> (*) now, this phrase by Ctein made me laugh out loud: "3. 
>> *Pragmatically*—pull out some of your lenses that still have depth of 
>> field markings on them." I had barely noticed the disappearance of the 
>> d.o.f. markings in glass for digital photography. Amazing.
>>
>> Fernando.
>> -- feeling somehow happy since I'm figuring out how to get rid of 
>> mdnsNSP.dll
>> ever faced this one? ;-)
>> Seems I'll have to reboot, what a nuisance.
>>
>> Chuck Norcutt wrote:
>>     
>>> No, the planned print output is what determines the acceptable circle of 
>>> confusion.  As long as the CoC is in the equation the maximum print size 
>>> has already been defined... except for Moose, of course.
>>>
>>> Chuck Norcutt
>>>
>>> Ken Norton wrote:
>>>   
>>>       
>>>> Yes, but I think he's completely wet.  I learned from you, Chuck, that DoF
>>>> is a printed-output issue, not a lens-camera issue.
>>>> AG
>>>>     
>>>>         
>>     

-- 
Dr. Fernando González Gentile M.D.
Av.L.P.Ponce 1526B - 11600 Montevideo, Uruguay.
Phone: +598 2 7084858
Fax:      +598 2 7087396
<fgnzalez@xxxxxxxxxxxxx>



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