This is going to be an odd post. It is not a lens test, nor advice for choosing the right lens for the job, but rather my own thoughts about a lens when I pick it up and use it.
These are honest thoughts. As honest as I can be with myself about a crucial part of the creative process. I will rate them from 1 to 5 for results/confidence.
Starting from the wide end.
12-40 f2.8 Pro. This lens leaves me in two minds.
If I am using it for landscape work, I have no issues with it what so ever. I know it is a good performer into the corners and across the range and can produce "A" grade images with care. Stopping down is good for depth of field, but not overly necessary for sharpness. The lens post processes well, supplying a feeling of an un moulded image, waiting for finessing. 4.5/4
As a work or general lens, I like it at the long end, but have little practical use for the wider end. I have a problem with wide angle lenses, use them sparingly and always feel they add too much clutter to a composition. 17mm (35mm) is my usual wide limit, but you never know when your client will ask for a group shot at close quarters. This lens still gives me the jitters a bit. I feel focus issues are more common with it (feel, don't know for sure), especially on the non firmware updated OMD bodies (yeah, I know..) and the bokeh it displays, pleasant enough for portraiture, exaggerates these misses. It looks to wash out some images when shot into the light, but I may be being harsh. I also feel it is sharper at close distances, but that tends to go for many lenses due to atmospheric conditions etc. 3.5/3.5
Edit. It turns out that the images I have liked most from this lens have been jpegs taken on the Pen F. The built in corrections for the lens look to my eye to be near perfect and I will be using jpeg/RAW files together until I am sure Lightroom can do as good a job as the Olympus engineers.
17mm. Great for the job it is designed for.
For street photography, where composition, timing and subject relevance outweigh sheer quality, this lens is ideal. I would like it to be a little better performing across the frame for landscapes, but I am sure I would manage (it's a lot better than my Canon 17-40L). The lens "feels" sharp in it's rendering, especially in the way it's bokeh transitions, a lovely mix of micro contrast snap with good coherence. It's accurate and super fast in focus and smooth in operation and the MF markings are a must for zone focussing. It took a while, but I am more than comfortable with it, indeed it is one of the three lenses (all primes) that I rely on. Part of my need for the above zoom comes from this and the 12mm lens's supposed weaknesses in the corners. 4/4.5
25mm. The must have?
This one is a confusing lens. I feel like it should be more than just the stable "nifty fifty". The focal length is just not used much unless I make myself. I often go out with it alone, deliberately trying to become comfortable, even reliant on it, and it tends to be my "one lens" option. I must confess, if I lost it I may not replace it or I may go back to a Leica 25mm that I feel has more character (flaws) and perceived snap (micro contrast), but then I would most likely get the Pana 20mm (but I have the 17mm..oh crap, too confusing). It is very sharp at all apertures (with a little CA wide open), contrasty, has some genuine sparkle and a good close focus, so I should not complain and I even feel the slight regret at selling the Leica is wholly unfounded as the lens has less erratic behaviour. It is most often used as a faster backup for the 12-40 for work or as the fourth and least used lens in my all prime street kit (i.e. not used enough). My wish is to use this lens instead of the 17mm as I feel the 50mm equivalent is more dramatic for street, but the 17mm is so good at getting the image. I do however always use it for night shooting, because of it's contrast and brilliance. I think it is good enough that I would not bother with the 25 f1.2 super lens for 5x as much. 4.5/3.75
45mm. This is my warm-fuzzy.
I love this lens. I cannot even say I use the focal length that much, but I love this lens. A bit like the 25mm, the focal length tends to one that I make myself use, but I never regret when I do and it is a no brainer when used with the 17mm on another body for street shooting. If I could only have one portrait lens, this would be it. It shares both the warmth, lush colour and contrast of the 75-300 zoom and the genuine and very grown up sharpness of the better Olympus lenses. I also find the focal length more versatile and cleaner (more decisive) to use than the 25mm, which often leaves me neither close or far enough away. My only wish would be for better close focus like the Panasonic. 4.5/5
40-150 Pro. My reliable work horse.
From a rocky start (re boxed and siting at the door for return), this lens has recovered to become my work horse lens. It was originally purchased for landscapes and will regularly do this work, but as a low light tele for sport and stage work it has really come into it's own. The shock of strong CA at the wider end and a strange "fuzzy" softness that shows up in strong light (possibly focus-Bokeh related) are being accepted in light of it's lightning fast AF, overall sharpness and versatility. I do not like the slight "ringlet" bokeh in all circumstances, but that gives me a reason to use my primes. 4/4
75mm f1.8 This is my "hot" spot.
I never regret using this lens. Some say it is a little long to be useful. My wish would be for it to have been slightly longer (100mm f2?), allowing me to get away without the big pro zoom. There is nothing to criticise, except it's habit of making me unsettled with other lenses (like Hi Fi gear, the whole tends to be judged by the possible performance of the strongest, but is limited to the actual performance of the weakest part). The 17mm is supposedly far below it in objective performance, but I think they make a good pair, the 45mm renders quite differently giving me options in look and the 25mm is technically close, often accompanying it as the fast support to my zooms when working. When I tested sharpness against the big zoom at 75mm, it was too close to pick, but the bokeh, speed and size of the 75mm makes it my preferred option. 5/5
75-300. The slow poke with some real punch.
How is it, my cheapest zoom, and nearly my cheapest lens, with such extreme specifications for it's pricing is one of my favourites? it is so cheap that I have sold and re bought it without feeling gutted (a similar story to my 70-200 F4L Canons, I had 3!). It has terrific perceived sharpness and is in real terms very sharp at the short end through to 200mm and pretty good at the long end. It is really long, pulling of shots, I have never been able to do without a monster lens and even though it is slow in aperture, it has good bokeh rendering and beautiful colour. There is not really a weak area in the package except average grade build quality. 4/4.5
14-42 kit (manual zoom type). Not rubbish.
I like this lens. I like that it promises nothing, but delivers plenty. If I am travelling really light, it gives me a decent wide angle to go with the 45mm as the fast long option.
Lenses are funny things. You buy them intellectually and/or lustfully, but only after using them for a while can you really tell if you like them. I am generally happy with the balance of my kit for the first time in a long time. It is not perfect, but it is probably as close as I can expect from one brand alone (something that I could not do with Canon in 2013, but could do now) and is more than I need really. Unlike my Canon days though, I feel no guilt about my excess as nothing cost more than it should (except maybe the 25mm?), it can all be carried and all lenses deliver.
So, how do I rate them in my head as I go out the door?
Will only leave behind if there is really no use for it (landscape); 75mm.
Will only leave behind if using pro zooms for work/landscape; 17mm and 45mm.
Always taken for work/landscape otherwise left behind; 12-40 and 40-150.
Will leave behind unless needed specifically; 25, 75-300, 14-42.
What could I survive on, if it was just for me?
The 75, 17 and 45 would get me through (and maybe the 25). This is the 1 camera mated to 1 lens kit (Pen F + 17mm, OMDn + 75mm, OMD + 25mm, OMD + 45mm each set up for best use of their respective lens).
And what would I buy if money was really no object?
The primo kit would be 12mm Leica, 42.5 Leica, 75 and 300 primes.