What focal lengths do you use most? Keep those.
It seems I go through focal length "moods."
Years ago I was using strictly 28mm, 50mm and 90mm but that was my first Leica kit. I was carrying 2 M bodies, an M2 with the 28mm Kobalux and an M4 usually with a 50 DR Summicron or a 90 Elmar. That was pretty much the perfect kit in my opinion.
Since then I've owned way too many cameras and lenses but always come back to a select few focal lengths. Now I'm shooting an M9 and have started to settle down to just a few lenses.
I've had a Super Angulon 21mm f/3.4 for over a year now and it is one of my favorite lenses. Definitely one of the sharpest and finest optics I've ever used. Yeah, it has colored vignetting on the M9 but that can be fixed in Cornerfix or converted to grayscale from raw.
I just fell back in love with the 28mm focal length using a 2.8cm f/3.5 Nikkor on an Amedeo adapter. It's fantastic but I'm still debating on whether or not to keep it.
I've gone through six 35mm lenses in the last eight years and can never seem to let go of the focal length no matter what i do. I could definitely live without it but life wouldn't be as fun. On the M9 a 35 is just about perfect for a one-lens walkabout.
At times many of us have had numerous 50mm lenses at hand. Only once in the last 9 years have I had just one 50mm lens and that is my DR Summicron, the lens I will forsake all others for. Can't be used on the M9 in anything other than close up mode though so I have a few Soviet 5cm lenses and a 5cm f/1.4 Nikkor which is my new go-to.
I tried to like 75mm and the lenses I've used have been stellar but it is too close to 50mm and 90mm to be useful (for me.) With a 50, it's one step closer and with the 90, it's one step back, that's how I see it.
I've also had a few 90mm lenses but after I got my 10.5cm Nikkor, none of them stacked up. I just love the long focus Sonnar look. I've used 90 Elmars, Elmarits, Tele-Elmarits and Summicrons but I just like the 10.5cm Nikkor better. Everyone has their own taste though.
As for 135mm I just can't get behind it. i love the compression of subject and the ability to reach out but the M9 rangefinder just doesn't have the magnification for critical focus of the 135mm focal length unless you use the 135 Elmarit with the goggles. But then the camera becomes a bit massive. If you need it, you need it. I might get a 13.5cm Nikkor just to have around but only once or twice in the last few years have I actually needed that much focal length on a scene where I couldn't get to the subject much closer.
So, in a nutshell, for me it's 21mm, 35mm, 50mm and 105mm. 28mm is definitely growing on me again since it's a focal length I gave up for a fast and sexy 35mm years ago. Give me non-distorting slower lenses any day though.
If I had to choose just two focal lengths though, it would be 28mm and 50mm.
Phil Forrest