In the various reviews/opinions/comparisons that abound on this site people ofen report on lens flare. It seems to me that there are at least four kinds of flare, and reviewers don't always make a distinction as to which kind they mean when asserting that lens "A" has little/some/a lot of flare.

Here are some descriptions of the 4 kinds that I see (there may in fact be more) I've used my own non-technical names - feel free to supply the true optical names if you know them.

1. Veiling flare - overall fogging that adds exposure to shadow areas and flattens image without producing distinct artifacts. Example: Thin Tele-Elmarit without lens shade. Not always optical in nature - can come from reflections inside the lens barrel/camera body.

2. Rainbow flare - bright colored arcs near frame corners when shooting close to the sun. The Contax-G 90 and Nikon 85 f/2 suffer from this, as does the pre-ASPH 21 2.8. Possibly just an extreme version of (3). Clearly a function of glass design only. All the lenses that do this have a concave surface somewhere near the front that acts as a mirror lens - focusing an image FORWARD which then reflects off another element BACK onto the film. With the Nikkor 85 you can point the lens at a bright light source and project a (relatively) sharp image onto a piece of paper held in front of the lens (but offset so as not to block the light source).

3. Specular flare - the classic multiple circles/hexagons lined up across the picture from sun or other bright light source in or out of the frame. This seems to be especially prevalent in complex SLR wideangles and much less so in the rangefinder lenses I've tried (Contax, Leica and V'lander). Extremely variable frm one lense to another.

4. Halation - very localized light "leaks" from bright areas into adjacent shadow areas. Noticeable as halos around brilliant objects (chrome water faucet, e.g.) surrounded by shadow or as glows around dark objects against bright light (tree branches against sky). Seems common to all my ('79 -'89) Leica lenses and may be a function of strong contrast piling on more light than film can handle rather than an actual optical phenomenon. Present in 90 'cron, 90 TE, 35 'cron to one degree or another. Seems to be emphasized if there is also a colored chromation aberration halo.

To my eye, the biggest source of type 1 flare in the thin TE is the rear edges of the lens barrel and focusing cam barrel. On both of these the ridged black baffling ends about a mm from the end of the tube, leaving a somewhat shiny rim which WILL reflect a bright light source if it is about 1/2 a picture diameter outside the frame so that its project image falls on the shiny area. Easily fixed by a deep lens hood.

And just a flare aside. The most extreme flare (type 2) I ever saw was in the 15mm Nikkor f/3.5. Taking vertical pictures indoors under flourescent strip lights I got sharp focused (but upside down and curved) images of the overhead lights superimposed on the FLOOR.

The issue is now open for debate.

-- Andy Piper (apidens@denver.infi.net), May 28, 2001

Answers

Then there are some lenses that seem to be nearly totally flare proof. I can't think of a single image taken with my either 40mm Rokkor (multicoated version) or my 90mm Elmarit, that have any of the flare types you mention above. To me, the worst offenders are the 16 element slr wide to tele zoom lenses. You can't use a good deep hood on them either because of the angle of view at the wide end.

-- Andrew schank (aschank@flash.net), May 28, 2001.

Useful classification. IMHO, no lens is flare proof, and even the best can in some circumstances show extreme symptoms of at least the #1 type of flare.

I get pretty severe #1 type veiling flare with my Summicron 50, latest formulation, even when there is no direct sunlight falling on the lens, just a 180 degree backlit subject, such as someone's face just inside from a very well lit balcony.

-- Mani Sitaraman (bindumani@pacific.net.sg), May 28, 2001.

Type 1 flare is the most evident, of all my Leica lenses, in the collapsible Summicron. Type 2, I don't believe I've noticed. Type 3 is not unwelcome when shooting with a reflex, so that I know in advance what I'm getting. I have to use extra care with the Leica M's to avoid it. When can't see it in the finder, I have no control over how it will work in the composition. I'm talking about the row of purple circles, here. I gather that type 4 is the one that takes on the shape of the diaphragm, corresponding to the number of leaves. Though I guess the "row of purple circles" (type 3) does this, too. I agree this seems to go with retro wideangles. I notice it especially with the 24mm and 28mm Nikkors. I't probably there with my 20mm f/4 Nikkor too, but I've never put it to the test.

-- Bob Fleischman (RFXMAIL@prodigy.net), May 28, 2001.