Musee Des Beaux Arts.
Many photographers I know, and many photographers who broadcast on YouTube and DP Review, look down on any zoom lens that isn't f2.8 or faster all the way through its focal lengths. The idea being that you'll finally be able to shoot in low light situations without difficulties. Another part of the supposed allure is "bokeh" (which really refers to the quality of the out of focus areas but which has been bastardized by common misuse to mean any out of focus background) or one's ability to easily throw a background into an anonymous blur of visual ambiguity. At a certain level there is also a wide spread belief that because "faster" zoom lenses are bigger and more expensive they are able to make images of better quality. By that I mean higher sharpness, butch-er contrast and more resolution.
Most of the f2.8 standard zooms are 24-70mm focal length range lenses which, for me, means some wasted engineering at the wide end and a total lack of happiness at the (modestly) long end of the lens. They are certainly not providing a focal length at the "telephoto" end that I find useful. Too short by about 30mm....
In addition to being frightfully expensive (and too short) the 24-70mm, f2.8 zooms are much heavier than their more pedestrian counterparts. Unless one is constantly shooting in low light, or training to carry weights around all day, these lenses represent an overkill case that's almost funny. My preference in lenses, regardless of your chosen system, is the new classic 24-105mm f4.0 or the Nikon version, the 24-120mm f4.0. Yes, you might "lose" a stop at the wide end but you'll gain a much great range of focal lengths and, oddly enough, you might find the slower lenses to be just as sharp at f4.0 or sharper.
I wish that Pentax made an f4.0 constant aperture zoom lens in the 24-105mm range, or even better, in the 24-120mm range but, sadly, they don't. What they do make for the full frame K-1 is a nicely compact 28-105mm f3.5-5.6 zoom lens that makes very good images, indoors and out.
Counterintuitively, I took the 28-105 with me to Canada to shoot in just about every situation. Belinda loves museums so the big Musee Des Beaux Arts was fixed on the radar from the beginning of our trip planning. I knew that it would be mostly darker rooms with brighter lights just on the painting and sculpture --- but my interest was not copying art work but making photos of the interior spaces, the venue and the people appreciating the art. In the "olden" days I would have taken several different prime lenses, each with a fast f1.4 or f2.0 aperture. But this was vacation/holiday and I just didn't have the energy to switch, switch, switch lenses all day long. Not if an alternative existed...
The advantage of a mid-brow, standard zoom lies in its smaller size, lighter weight and also its lower acquisition price. My total investment in the system in hand at the museum was about $1500. That was the price of a used, but mint, K-1 body, with 36 really nice megapixels, and a brand new standard zoom. One of the key features that makes the K-1 a good travel camera is that it has really great high ISO performance and very effective in body image stabilization that works with every single lens you attach to it.
Instead of relying on a wide aperture to provide a fast enough shutter speed to both hold the system steady and also freeze subject movement I went in a different direction and depended on the camera to produce clean raw files at ISO 1600 and 3200 while leaning on the I.S. to allow me to shoot at shutter speeds as low as 1/15th of a second with no real image quality concerns. Even when stuck at f5.6 and 105mm I felt that the images were as good as any I'd gotten with older, fast lens techniques. It also meant that I didn't need to carry along multiple lenses or multiple lens and camera combinations.
The Chinese Gardens at the Botanical Garden.
Where a small, less highly spec'd standard zoom comes into its own, though, is in exterior photographs during the day. Overcast, sunny, raining, etc. It doesn't really matter as long as you have a camera that delivers ISO performance that matches your taste in ultimate image quality. For the image just above I was shooting at ISO 100 and f8.0. I'm sure my shutter speed was somewhere around 1/400 or 1/500. I can't really imagine what advantage an f2.8 zoom lens would have had in this situation. By f8.0 nearly every lens I've used performs very well and having both the extra zoom range and the smaller lighter profile made for a more enjoyable shooting day.
The reality of lens design is that lenses with smaller apertures can be made to a higher performance standard than faster lenses with bigger glass elements. It doesn't always happen but the math points to smaller lens elements being easier to make and quality ensure. I presume that there are also more difficulties in assembling and calibrating the more complex designs required by faster lenses.
I think Pentax struck a nice balance between price ($499 US) and overall performance. But I'm also impressed by the lens I left at home; the Panasonic Lumix 24-105mm f4.0 (constant aperture).
The optical performance of the Lumix is really superb with the lens mostly at a high level for sharpness and contrast already at wide open. I find the two ends of the focal length range to be excellent at f4.0 while in the middle ranges, if you want the corners to be sharp you might need to stop down to f5.6. The lens and S1 camera together, using dual I.S., are as close to perfectly stabilized as I've found across all systems for sensors bigger than micro four thirds. And its performance with the 24-105 is close to that of the Panasonic G9 with the Olympus Pro 12-100mm. Pretty amazing.
Given the sensor performance of the S1 I can only imagine that the system would be great for travel. It's too bad I wasn't ready to bring it along on our travel adventure but I didn't have enough hands on experience yet with the camera to be comfortable. Next time.
Anyway, don't reflexively turn your nose up at a slower-than-f2.8 standard zoom lens. You may be passing up a sharp, well behaved optic that fits into your travel and shooting parameters much better than a more "prestigious" fast lens. And you'll save enough cash opting for the slower lens to pay for the plane tickets for your next adventure.
That's all for now. Write as comment. Tell me about your favorite mid-range zooms. I'd love to know what's out there.....