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View Full Version : Nikkor SW 90/8.0 vs 90/4.5 light fall off?



Roger Hein
29-Aug-2004, 18:25
Could someone tell me if the Nikkor SW 90mm lenses (f/8 & f/4.5) would exhibit the same light fall off towards the edges when used at the same aperture (f/11 or smaller)? ie. is their any advantage to the 'faster' lens other than being brighter for focusing? I seem to remember reading a past post saying the 'faster' lens would have less fall off than the 'slower' lens at any given aperture and wondered is this is in fact true? Thanks!

John Cook
29-Aug-2004, 18:50
I have owned both and not noticed any difference. Just checked the image circle specís and they are virtually the same. The f/4.5 lens shows 154mm @ f/4.5 and 235mm @ f/16. The f/8 lens shows 154mm @ f/8 and 235mm @ f/22.

The f/4.5 is much nicer to focus under dim model lights in the studio, the f/8 gives me no trouble on location in broad daylight. Nice thing is the weight of the f/8 doesnít put a big strain on the front standard of my flimsy wooden field camera. The smaller filters and greater ease of reaching around to the shutter controls are nifty as well.

Neither lens, as with all 90's I have used, lends itself to heroic swings and tilts.

Tom Westbrook
29-Aug-2004, 18:56
I don't have an answer, but here is a good article on lens vignetting that might help: http://www.vanwalree.com/optics/vignetting.html.

Michael S. Briggs
29-Aug-2004, 19:15
The Nikkor-SW lenses are of the same design type as the Biogon, the various Grandagons, and the various Super-Angulons. These lenses have large diameter outer elements which have negative power which tilt the pupils, improving the uniformity of illumination. Regular lenses which don't use this design techinque, which means most LF lenses, have illumination at the image plane that goes as (cosine theta) to the fourth power. The design technique of the Nikkor-SW and similar lenses theoretically improves illumination to the third power of cosine theta.

The German manufactuers (Rodenstock and Schneider) publish graphs of relative illumination for their current lenses. Their wide-coverage designs are close to the expected cosine to the third behavior. I know of no comparable published graphs from the Japanese manufactuers (Fuji and Nikon). From the design type that is seen in the cross-section diagrams of the Japanese wide-coverage lenses, I expect similar behavior.

Most lenses, when used wide open, don't deliver their specified maximum aperture to the corners of the image because the lens elements have insufficient diameters and cutoff some of the rays -- this is called (mechanical) vignetting. Once a lens is stopped down enough to eliminate vignetting, typically 1 to 3 stops, then the illumination will follow the rules mentioned above. The illumination curves of the stopped down lens are mainly determined by the design and there isn't a general reason to think that a larger aperture lens will have better illumination than a slower one, when both are stopped down enough to eliminate vignetting.

My opinion is that evenness of illumination isn't a reason to choose between the two 90 mm Nikkor-SWs. I suggest choosing based on maximum aperture for focusing, cost and weight.

Don Boyd
29-Aug-2004, 22:39
I own the 90/4.5, and while I like the lens' image quality, I have had problems with flare in the images. Using the Lee standard compendium lens shade almost always resulted in a vignetted transparency. I have had to take great pains to shield the large front element with my hat/shirt/film envelope (choose 1). I have purchased the Lee wide-angle model hood but haven't had a chance to use it yet. Often shooting in low light conditions, I have appreciated the additional light that this faster model gives me.

Roger Hein
30-Aug-2004, 06:51
Thanks to all for the helpful info. Looks like the 'slower' lens will be my choice.

Gem Singer
30-Aug-2004, 08:30
Good choice, Roger. The difference in size and weight between the f4.5 and the f8 is considerable. You didn't state which camera you will be using, but the huge size of the rear element of the Nikon f4.5 90SW sometimes makes too large to use on a small 4X5 field camera. The difference in cost between the 67mm. filters for the f8. and the 82mm. filters for the f4.5 can be considerable. The Nikon f8 has the largest image circle of any of the 90 f8's available (235mm.). It comes highly recommended as the best buy in 90mm. wide angle lenses (see Kerry Thalmann's website).

Darryl Roberts
6-Feb-2008, 13:48
What if I were to need a lens for night architectural work? Am I right to go with the 4.5?

Andre Noble
8-Mar-2008, 20:31
I've owned sharp samples of both. I know you didn't ask about relative sharpness, but optical performance wise, the f8 is clearly superior to the 4.5 version.