Vignetting

[gadrian]

Hmm there is a slight level of vignetting..

Correct me if I am wrong.. there are three (natural,optical and mechannical) types of vignetting..

Optical and natural vignetting are basically caused due to optical design, more apparent on wide angles then on tele due to the optical cos4 law of illumination fall off..

Will mechanical falloff (vignetting) is due to a an object protruding/obstruction of the field of view of the lens.. this can be caused by a lens hood that is too long.. or stack filters.. or a combination of both..

You image does exhibit a level of light fall off around all the corners.. more noticable on the top left due to the more contrasty white sky then the dark buildings.

This is inherent of most wide angles, surprisingly the even the "trinity" 17-35 does suffer from light fall off.

 

[showtime]

nickmack is misinformed... thats light fall off not vignetting...
he made an elementary mistake...

 

[showtime]

i think there are already words that have been to define certain things... lets not reinvent the wheel and use them correctly so that people wont be confused... technically, gadrian you are correct about optical and mechanical etc... but the terms as widely used by photographers is simply light fall off, and vignetting respectively...

and the difference is very clear cut...

thus i still maintain my stand that the picture exhibits light fall off.. and its not really extreme..

and also, light fall off occurs not just at extreme wide angles... it occurs when the lens is used at wide open apperture... NOT wide angle... and this occurs with EVERY lens... thus it is not surprising that the trinity lens that was refered to suffers from the problem..

wanna get rid of fall off? stop down a couple of stops... shoot at smaller appertures... this is already the norm for architecture and lanscape photography... so most should not have much prooblems...

look at the sample picture, shot at F3.5
thats wide open for that lens, the 18-70 dx by nikkor. perhaps shoot at f8 insead.

 

[teerex]

nickmack is misinformed... thats light fall off not vignetting...
he made an elementary mistake...

nickmak - no offence, just needed clarification on term used. Thanks for pointing out anyway.

showtime - may I conclude that shooting at a smaller aperture, f8 as recommended will be able to eliminate the light fall off problem in the picture?

sulhan, gadrian and 2100 - thanks for your info.

 

[bLight]

is there any image processing util or PS plugin that can rectify vignetting? I usually either crop the image or manually adjust the corner in PS when i see them. Would be easier if there is a tool to do it.

 

[teerex]

is there any image processing util or PS plugin that can rectify vignetting? I usually either crop the image or manually adjust the corner in PS when i see them. Would be easier if there is a tool to do it.

I do not think that there are any plugins to rectify vignetting. But since your using PS you can use the clone tool to correct the darkened portion of the picture. There may be other ways, perhaps the experts here can suggest.

I did a quick pp with a freeware on the top left of the picture. May not be good enough, but can be done.

Here's the corrected picture

 

[gadrian]

showtime.. yes you are right.. it happens on all lens.. as this is an optical design..

Though it is more inherent on wideangles then on teles..

I did note that the image did suffer from light fall off..

Perhaps I should state more clearly..

Natural or Optical Vignetting is more commonly referred to as light fall off by photographers..

Though there is distinction between the 2. Optical Vignetting (light fall off) can be cured mainly by stopping down the lens 2-3 stops..

However Natural Vignetting mainly only be benefit by using a center ND filter.. such that would be used by many Xpan users (30mm f/5.6).. or anyone that has used a Hologon 16mm f/8.

Where as

Mechanical Vignetting is more commonly referred to as Vignetting by photographers..

Two books that you we can refer too when dealing with optical designs.

1.Sidney F. Ray, Applied photographic optics, 2nd ed., Focal Press, 1997.
2.Warren J. Smith, Modern optical engineering, 3rd ed., McGraw-Hill, 2000.

 

[showtime]

nickmak - no offence, just needed clarification on term used. Thanks for pointing out anyway.

showtime - may I conclude that shooting at a smaller aperture, f8 as recommended will be able to eliminate the light fall off problem in the picture?

sulhan, gadrian and 2100 - thanks for your info.

yes... 2 stops should be sufficient enough for most lenses...
and with regards to photoshop removal of fall off, i'd do it manually...

 

[gadrian]

Btw.. NC4.1 also has a vignette control tool.. try it out.. its quite interesting.