Originally posted by Williquette OK guys I'll give you a little more information about me. My travel overseas is for work, I'm a missionary teaching in 3rd world countries. When I'm overseas I take my camera and I have limited opportunities to get away and take pictures of the landscapes and the people. I want to take high quality pictures but the convenience of a super zoom is very attractive because it allows me to travel light. If however using a super zoom will compromise the quality of the pictures then that's not what I want.
I'd take the 16-85, a 55-300 PLM and wide aperture 50 for low light.
There are many instances where the 18-300 will not seriously affect your IQ, in that it will adequately resolve the important elements of a scene. I used to carry a Sigma 18-250 for the same reasons you want to. We got some very nice images with it. Some of the comparison images were good enough they were selected over images taken with my DA*60-250 for publication. While the DA*s have a higher top end, on many images you won't see a difference. In the end, it comes down to "Will you have time to change lenses?" In my case, travelling with groups of people and having a responsibility to keep up with the group, my 18-250 meant I had the right lens on the camera all the time, and could carry a camera case as opposed to a camera bag. That's an advantage that is often understated in these types of discussions.
Sometimes using higher quality glass, instead of getting a better image results in getting no image. There's a reason these lenses are popular. One often ignored by the tech heads for whom everything is about technical perfection in glass, but who are totally impractical for many shooting situations. In the end, in your case, where you don't have a lot of time to shoot, the 18-300 to cover everything, and then a 21 ltd, 35 2.4 and 50 1.8 would make a nice light easy to manage travel kit. The primes would be for use use on those occasions when you have time for lens changes and zooming with your feet.
I have friend who shoots an 18-250 and has come up for fall colours, and when we come home and look at the images, it's composition etc. that makes the images. I've never once seen an image where one of mine was better because I was using better glass. The added value of "better glass" is for the most part exaggerated. The fact that you might see a small difference if you put two similar images side by side in no way suggests you'd enjoy one image more than the other. Especially since much of the advantage of better glass is lost when you reduce the image size for conventional viewing on a computer monitor or up to 11x14 print.
The worst lens I own an old FA 28-200 takes images that look great on a 4k monitor. You can over think these things.