My contribution for a portrait exhibition in Bonn

Title: "WHO ARE YOU?"

Excellent collection!

Evening stroll - Leica Q2

Every time light passes from air to glass and glass to air some light is reflected at the air-glass boundary, and goes back into the air or back into the glass. Then it ricochets around and some goes back out the way it came and some is absorbed by the non-reflective interior paint of the lens but some reaches the sensor/film as "flare" and lowers colour saturation and contrast.

The more air-glass boundaries you have the more light is reflected instead of transmitted, so the short answer to your question is that you want lenses with the fewest number of elements.  If you look at Roland Vink's database http://www.photosynthesis.co.nz/nikon/lenses.html you will see that the number of elements is lowest for manual focus lenses with focal lengths between 85 and 135 or so. The very highly-regarded 105/2.5 Ai-S, eg, has 5 elements in 4 groups and the 24/2.8 Ai-S has 9 elements in 9 groups, so flare will be about twice as bad in the 24mm and saturation and contrast will be less. Lens coatings make a big difference, and modern coatings are why modern lenses can have more elements and not have problems with flare, but, coatings being equal, fewer elements is what you need to look for. 

The reason older cameras have more saturated colours is not the CCD sensor. All digital sensors are monochrome, and the coloured image is created by the Bayer array of coloured filters over the photosites which computer power turns into a coloured image. There is no difference between the camera doing it and you doing it, except that what you get from the camera is the way Nikon engineers thought looked nice and what you get from the computer is what you think looks nice. Older cameras had more saturated colours because people transitioning to digital expected pictures to look like the slide film they were using, especially Fuji Velvia, which was very saturated and contrasty, so that is what the engineers gave them by default.

People often say that slides had a vividness and impact that they don't see with digital images. The reason is the same as the reason for the vividness and impact of the stained glass windows in medieval cathedrals: they are lit from behind, and increased brightness increases perceived saturation. Your images will be more vivid if you increase your monitor brightness, so you can't judge how good your images are out of the camera if you haven't adjusted your monitor brightness carefully, and you have to be careful asking other people's opinion, because they won't see what you see if their screen brightness is different. You have to be very careful about prints, because a print is reflected light so it does not benefit from the magic of transmitted light and a printed image will look terrible if you prepare it on a too-bright screen.

I thought I had responded but seem not to have pushed the button.  I'm not terribly well versed in the subtleties of color, and don't usually worry too much about it, but I particularly like the way that the old 200/4Q lens gets colors, as well as just general nice looks, especially with greens.  This may have something to do with the fact that I use it mostly for bug hunting in the grass and cattails, with a bunch of extension tubes, but in any case I like it.  It's a nice lens actually to use, anyway, and it is quite comfortable with about as much extension as you can fit on it (I often use all 68 mm of my old Vivitar set), making it a somewhat odd long focal length macro.  Since this lens can be crazily cheap at times, I think it well worth playing with anyway. 

I'm traveling and have no access to any examples, but if you like chasing bugs this is a surprisingly enjoyable one to try. 

Example with  the D80 and AFS 17-35/2.8