Just posted much of this on LUF - may be of interest here as well.
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I have just bought the 24-90SL to go with the SL body, and took it on a long weekend to Bologna. I deliberately tried it as a single package for travel and street, knowing that normally I would take my M240 and M lenses (probably 28, 50 and 75). I had a Billingham 1.4 bag to carry it around in, but in practice normally carried it around in one hand using a Spider Pro hand strap, hanging at my side. I taped over the logo and red dot, just to avoid catching the eye. I typically used it in AutoWB, AutoISO, AFs, A mode, wide open by default.
My conclusions were:
- Carrying it around all day (with breaks for coffee, lunch, wine etc) was not a major problem, although I noticed the weight.
- Leaving the lens cap off caused me no worries, as the lens hood is big enough. Like the Apo-Summicron-M 75, but unlike the Apo-Summicron-M 50, whose hood is a bit too small to provide physical protection IMO.
- I'm a biggish guy, and I didn't feel I stood out particularly with SL in my hand at my side (i.e. I am more noticeable as a person than as a photographer). My wife confirmed this. OTOH, I did not feel particularly discreet swinging the camera to my eye and holding it there, and I suspect I was more noticeable than I would have been with the M, particularly in more confined places, such as cafes and crowds.
- In normal scenarios, the SL was blindingly fast to focus and expose, quicker than the M, even allowing for not changing lenses.
- I found spot focusing was often a pain, because the spot often ended up on a blank surface which did not give a quick focus, and moving the body or spot location was distracting (once you've fixed composition, you don't want to move the camera, and moving the spot often leapfrogged the point you wanted to focus on). Small patch focusing was ideal for most cases, and using the joystick to move it was a "joy".
- Occasionally I felt the need to switch to manual focusing (through railings etc), and I would really appreciate a single button press option to switch from AF to MF and back. Hope this comes in future.
- I used Exposure Compensation a lot; assigning it to the top right button was OK, but in my case the hand strap made reaching the button with my thumb not instant. Future firmware should give one the option to directly assign it to a dial. In fact re-assigning dials for different uses should be enabled.
- In very low light, such as dark streets at night, AF would hunt and occasionally fail (TBH, I didn't think to try Multi-Field AF).
- I would really like a quick way to reset the focus patch to the centre. Eventually I got into the habit of resetting it after each shot, but a single button press, or possibly auto recentre would be useful.
- The SL lens appears to be flare-proof. The weather was bitterly cold, but without a cloud in the sky. I took lots of shots into the sun of Bologna's photogenic arcades and their shadows; I can't recall any ruined by flare.
- I set the camera on "no auto review" and sleep mode, and found a battery lasted most of a day. Wake-up delay was as irritating as on the M240, and about the same: 2 secs.
- The one total failure | had was walking into the tropical house at the botanic gardens from -2C outside. Condensation made it impossible to photograph the orchids!
- When speed of reaction is not an issue, composition on the SL is easier because of its zoom. I found I cropped my images much less than I typically do with the M.
- Using a hand strap with the SL was fine, but it limits finger movement a bit. As well as making it a stretch to reach the TR button with my thumb, I occasionally pressed the rear dial and changed mode without noticing. Not Leica's fault, but needs watching.
- Apart from issues mentioned above, I found the ergonomics of the SL exceptionally simple, intuitive and quick compared to a multi-button, multi-option, random layout alternative. (I have the OMD EM5ii, which is supposed to be one of the better ones for ergonomics).
Would I drop the M in favour of the SL for a similar trip in future? No, the M is smaller, lighter and more discreet, and in principle can take the same shots. The greater speed of AF is only one element in capturing the right shot at the right time, and the slightly easier composition with the M (no zoom to fiddle with and distract) combined with the slightly extended moment before a subject notices you, are real benefits of the M.
The SL worked exceptionally well, though, for such an application as this.
Whichever you have, you don't have to worry!