Vignetting on 15mm?

[David S]

I seem to experience mild vignetting with the 15mm, particularly at narrow apertures. Has anyone else noticed this, or does anyone have any suggestions to avoid it? (Other than wider apertures?)

Thanks in advance

 

[Doug]

Well, there's certainly "cosine law falloff", a natural effect that becomes stronger the wider the angle of the lens. This is widely called "vignetting" these days, whereas that term more properly refers to physical shading at the corners such as from the wrong lens hood or stacking too many filter rings. One noticeable difference is that true vignetting tends to be more abrupt while falloff tends to be a more gradual darkening gradient from center to edge.

So, yes, the 15mm Heliar does have noticeable darkening toward the corners due to falloff but I haven't seen any vignetting...

 

[Marc Jutras]

The 15/4.5 Heliar is best at f/5.6 and still pretty good at f/8. Wider or narrower than 5.6 is not as good. The problem is not only fall out but also sharpness. I try to shoot mine at f/5.6 all the time (f/8 is useable).

 

[Doug]

I don't know, ManGo! I do understand that lens "coverage" (illumination circle?) of view camera lenses gets larger as one stops down. A lens has better coverage stopped down than wide open, allowing more extreme camera movements... I don't know how this relates to falloff or vignetting.

 

[David S]

Thanks everyone. I certainly meant "falloff" rather than vignetting! Will stick with f5.6 or f8 and let you know the outcome!