Re: [ATM] TDE on a 6f6 mirror

[Dale Eason <atmpob@yahoo.com>]

It looks like camera lens vignetting to me.  You did
not get the full disk.  When the knife is completly
pulled out you should see both edges of the mirror. 
We don't see that.  Next try turning on the room
lights and turning off the LED.  So that we see the
mirror in normal light.  Next turn on the LED.  Keep
the zoom at the same settings for both.

I think you will see that only part of the mirror is
illuminated.  In reality you are only seeing part of
the returning light cone.

Your eye actually has a wider lens opening at this
point or perhaps you have faster feedback and can
adjust yourself so that your eye is not vignetted. 
Small digital and most video camera lens have a very
small opening inside of the zoom lens.

You seem also to have a lot of air currents that make
it look bumpy.  These bumps look different than the
last set so I think that is air currents.

I think Mike was refering to the classic sign of astig
when the shadows are not the same on the top and
bottom.  I think that is probably air currents and not
on the glass.

Dale Eason

--- Anthony Anconetani
<anthony.anconetani.atm@gmail.com> wrote:

> Good evening guys,
> 
> Vladimir, thank you for looking at the pictures.
> Yes, a bunch of
> things changed between picture 1 and 2. I wasn't so
> much interested in
> explaining the difference between the two pictures.
> Rather, I was
> guessing that the bright left side could be a
> reflection from the
> inside side of the mirror. But the more I think
> about it, the more I
> suspect the edge is just turned down.
> 
> Dale and Mike,
> 
> Well, I took two more pictures at about zone 2. Here
> is the first with
> the knife edge backed out.
> 
>
http://www.atmlist.net/contrib/anthony-dot-anconetani-dot-atm-at-gmail-dot-com/zone2_no_knife_crop.JPG
> 
> It doesn't look to me like the the camera is
> vignetting the light
> cone. I think that dark edge on the right is rolling
> down. Is that
> what you think Dale?
> 
> Here is the second picture with knife brought in:
> 
>
http://www.atmlist.net/contrib/anthony-dot-anconetani-dot-atm-at-gmail-dot-com/zone2_crop.JPG
> 
> This picture still bugs me. Without the camera, the
> rolled edge/TDE
> doesn't look as bad and I can see a faint
> diffraction on the right.
> Are digital cameras a little more pesimistic (or
> maybe unbiased 8-)
> then eyes?
> 
> Mike,
> 
> You mentioned astigmatism. Looking at the picture
> zone2_crop.JPG is
> lumpyness causing the astigmatism? Or do you see a
> bigger problem?
> 
> What's the difference between a "rolled edge" and a
> "turn down edge"?
> 
> Lastly, yeah blue LEDs... Too Cool...  I got that
> idea from some guy
> up in Illinois. 8-) Actually, I saw them in DigiKey
> and couldn't
> resist.
> 
> -Anthony, Round Rock TX
> 
> On Nov 19, 2007 4:02 PM, Mike Lockwood
> <melockwo@uiuc.edu> wrote:
> > Hi,
> >
> > Dale Eason wrote:
> > > There is the possibility that the camea lens is
> > > vignetting the right side of returning light
> cone.
> > > That happens a lot with small cameras with zoom
> > > lenses. It can also happen if the camera lens is
> not
> > > close enough to the knife.
> >
> > Good point.
> >
> > > To know for sure back the knife out of the image
> and
> > > then take a picture.  If the mirror is not fully
> > > illuminated then that is indeed the case.  If
> the
> > > mirror is completly lit then then edge is
> turned.
> >
> > Let me add to that - IF the mirror is completely
> lit then you have a
> > rolled outer ZONE, as well as TDE.  You also have
> some astigmatism
> > because the shadows are not symmetric, and/or
> possibly roughness or
> > turbulent air in the testing room.
> >
> > Let's hope that the mirror was not fully lit and
> the next set of
> > photos is better.
> >
> > I like the blue color.  :)
> >
> >        Mike Lockwood
> >
> >
> > _______________________________________________
> > ATM mailing list http://www.atmlist.net/
> >
> _______________________________________________
> ATM mailing list http://www.atmlist.net/
> 



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