PanoTools NG:
Re: Canon 5D MKII
Hans 2012-Mar-18 16:36:21
--- In #removed#, "pedro_silva58" <pedro_silva58@...> wrote:
>
>
>
> hans,
>
> thank you for replying.
>
> in the previous discussion in this thread, it was not clear (to me) that it was this sort of issue that was being discussed. i thought the issue was between-image differences, not within-image differences. my bad, i suppose!
>
> still, i don't understand how a vertical-travel focal plane shutter, like the one in the d7000, would produce this left-to-rite unevenness along the full long side. perhaps you would be kind enough to explain?
A vertical-travel focal plane shutter. is of course running from top to bottom as seen in landscape.
That is how almost all modern DSLR shutters work since the 1970s. It gives a shorter travel than the old time horizontal shutters and this gives you shorter exposures for full opening and with that syncronization of flash up to 1/200 sec with todays shutters.
As we take the images in portrait it means that the problem will be as in my examples.
Hans
>
> cheers,
> pedro
>
> --- In #removed#, "Hans" <hans@> wrote:
> >
> > --- In #removed#, "pedro_silva58" <pedro_silva58@> wrote:
> > >
> > > greetings!
> > >
> > > how are you guys so sure it's the shutter causing problems -- and not the lens diaphragm?
> > >
> > > whenever i've had this kind of problem i've always been able to isolate it to a single lens (at a time), and it happened with the couple cameras i tested, so i know in my case it was the lens. it kind of makes sense, too, it's very easy for a single diafragm blade to get stuck, more so than either shutter blade, especially since the latter tend to be electronically controlled (the fp shutter principle may be the same since 1883, but replacing mechanical springs by electrical micromotors made a huge difference in practice -- and don't "we" prefer practice over principles?).
> > >
> > > but since you experts are so quick to blame our modern shutters, for your exposure troubles... inquiring minds want to know!
> >
> > Pedro
> >
> > How do you mean the diaphragm should cause a linear exposure difference along the full long side from the edge to about 25% from the edge.
> >
> > I know this problem since 40 years of different SLR cameras. My Pentax 67 also had it.
> > On modern DSLR It is usually from 1/160sec and shorter.
> >
> > This is my 5D with a 24-85mm lens at 85mm and at 1/800 sec.
> > http://www.panoramas.dk/panorama/exposure-problem/shutterproblem1.jpg
> >
> > This is AYRTONS brand new Nikon D7000 with a Sigma Zoom at 200mm and at 1/160sec
> > http://www.panoramas.dk/panorama/exposure-problem/befor-after.jpg
> >
> > A fix is to make an adjustment brush in ACR along the side or you can make different Photoshop actions with a mask.
> >
> > Unfortunately it is very hard to get the adjustment controlled on different images with different bright and darker areas.
> >
> > The best solution is to do a large overlap. Minimum 30%
> >
> > Hans
> >
> >
> > >
> > > cheers,
> > > pedro
> > >
> > > --- In #removed#, Erik Krause <erik.krause@> wrote:
> > > >
> > > > Am 17.03.2012 22:48, schrieb Hans:
> > > > > Much of the problems with uneven exposure which you had on the first
> > > > > Leicas from 1925 are still the same, especially when you do
> > > > > Gigapixel panos you will figure out that the blender can not cope
> > > > > with even the slightest change in exposure from left to right side. A
> > > > > difference of 2-3 % is enough to give PTGui problems if you have too
> > > > > little overlap.
> > > >
> > > > That's all too true. And a good reason not to use too short exposure
> > > > times. The more time the shutter stays open, the less is the influence
> > > > of uneven shutter movement.
> > > >
> > > > But of course it's a pity that the vignetting correction model can't
> > > > cope with this kind of uneven lighting. Should be possible though, much
> > > > the same like vignetting correction works, too...
> > > >
> > > > --
> > > > Erik Krause
> > > > http://www.erik-krause.de
>
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