wwp@yahoogroups.com:
Re: Nikon 2.8/10,5 Sigma 3.5/8 or Tokina 10-17 ?
Alex Makienko 2009-May-11 14:47:00
Hans,
It is obvious for me that you mix effects having absolutely different nature, however in some cases they may have similar visual appearances. Grease causes diffraction and dispersion but rear filter adds reflection (I assume that photographer knows that the rear filter has also to be cleaned :-)). Physics of these effects is different.
I apologize, but I have nothing more to add. To continue we must refer to the fundamental optics, discuss drawings, optical schemes and formulas. I am not sure that moderators will tolerate this.
Regards,
Alex
PS: The pano you refer:
http://dimensions360.com/index.php?screen=show&id=707e2b69&galle...
had been taken with two or even three rear filters. Rear filters not always have multi-coating and reflections they add significantly degrade contrast and add parasitic lighting. Spots on the sky are caused by waterdrops - at this place wind is permanently blowing from the waterfall down the canyon and it is impossible to keep lens dry.
PPS: Of course you may call spots caused by waterdrops as "flares", the physics does not depend on terms. :-)
----- Original Message -----
From: Hans Nyberg
To: #removed#
Sent: May 11, 2009 10:10 AM
Subject: Re: Nikon 2.8/10,5 Sigma 3.5/8 or Tokina 10-17 ?
On 11/05/2009, at 4.37, Alex Makienko wrote:
> The spots in the image you refer have absolutely the same nature as
> here:
>
> http://dimensions360.com/index.php?
> screen=show&id=7087d155&gallery=9cbca271
>
> This pano has been taken under an intensive shower - dense water
> dust was coming from the powerful waterfall (yes, the lens had been
> thoroughly cleaned before and, of course, after shoting :-)). What
> you see there is IMAGES of waterdrops on the front lens of Nikkor.
Sorry Alex but that one is not at all the same. Take a closer look
at my example. It is obvious that you did not do that.
You also said "Shooting with a rear filter may increase flares
dramatically even in an interior"
Correct but a filter may do it similar as a thin grease layer will
do. Both are flare caused/increased by additional sources than the
actual lens.
The effect is very different also depending on the kind of light, A
large flood of window light like in my example is very different to a
sharp sun/light source.
> Here:
>
> http://dimensions360.com/index.php?
> screen=show&id=e222c0bc&gallery=a795c71e
>
> the nature of the spot is completely different. This is one of my
> worst panos and a pure example of Nikkor's FLARE.
Yes this is one of the many different flare types you can get with
the 10.5 and many other lenses.
But it is very easy to avoid it.
First of all do not place the sun as close to the centre, and most
important do not stop down as much as you do.
F4-5,6 are the sharpest with the 10.5mm and you have plenty of depth
of field .
At 5.6 it will not produce flare like this even with the sun in the
same place.
If it does your lens might be defect. I have managed to duplicate
this flare by stopping down to f22 but it disappears completely when
opening the aperture to 4-5.6
Note that other lenses may react in another way so it is important to
always learn you lens behavior for flare.
I checked a couple of others of yours and this one has some very
weird red flare spots which might indicate that your lens has some
specific problem.
http://dimensions360.com/index.php?
screen=show&id=707e2b69&gallery=324a5257
This one also has typical flare from a dirty lens. It does not look
like it is caused by water drops.
If this was taken with the 10.5 I would have returned the lens and
demanded a new example.
Hans
Hans Nyberg
Panoramas.dk<http://www.panoramas.dk>
Features Fullscreen Panoramas from the best VR Photographers in the
World
email: #removed#
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