The linked post below addresses a number of proven techniques for sharply focused images, and none involve a new $1900 lenses. The 24-70 lens is a superior lens, but you've given up a lot of focal length options for your cropped D7100, both on the long end and the wide end. You might be happier with any of Nikon's shorter 18-xxx lenses, like say the 18-200 VR: cheaper, lighter weight, VR-enabled, plenty sharp enough with good technique. If you want a super sharp lens well-suited for your D7100, find a used copy of the 17-55mm f/2.8 DX.

How to obtain sharp images in digital photography

Anyone who is serious about their photography, except for soft-focus and special effects, wants SHARP lenses but HOW SHARP? Perhaps since the advent of digital imaging, folks have become totally preoccupied with microscopic razor sharpness shod I say "surgical instrument" sharpness- sharpness beyond reality- sharper that we actually see things. Some of the photography looks like pasted-up cutouts, especially withy excessive post-processing sharpening. The way some photographers go on, you would think everyone is producing photo murals or viewing the vacation shots on the Jumbotron at their local sports venue or at the nearest i0max theatre. Some obsess over diffraction to the extent that the won't stop down the lens beyond the "sweet spot" and loose sleep over IQ at the expense of actually taking pictures!

Generally speaking, modern zoom lenses are pretty decent throughout their range but that won't necessarily optimally perform at every focal length and aperture settings as high-quality prime lenses of the same manufacturing quality. Zooms, however, have their obvious advantages and conveniences. In certain kinds of work, the should be the tool of choice to facilitate fast and spontaneous shooting situations.

In my own commercial and industrial work, I don't usually shoot sports but I do lots of work in factories, construction sites, and basically dirty environments. I walk around in the mud, there are sawdust, iron filings, welding sparks, airborne particles and the last thing I want to do is change lenses. There are fas moving heavy equipment and I need to focus, compose, and shoot quickly. My 24-105 on a full-frame body, hanginh on my neck, does the job! The shots are used in full-page spreads in corporate annual reports, advertising, and mural-size prints for trade show displays- sharp enough!

I have had (wise-guy) art director tell me they want "pictures so sharp I can see the dust" Really? In the studio, I can pop on a macro lens and shot medium format on my digitized RZ- but I do dust off the products before shooting them! Then the tall my ultra-sharp image and print their brochures on Xerox instead of high-quality offset!

Another gripe- I see shooters, who complain of soft results with their costly zooms and long telephoto glass because the are blurring the images with poor camera support techniques, insufficient shutter speeds, and focusing technique. The make tripods, grips, gunstock mounts, monopods, and all kinds of newfangled gambles for a reason. Some haven't yet mastered all the autofocus option on their menu or really know how to manually focus for extremely precise results.

There is a matter of budget unless of course, you are independently wealthy. How may lenses of different focal lengths can you afford? I do photography commercially and folks say "you can buy all the gear you want and write it off" My answer is write it off against WHAT?! First, you need to show a profit, manage your business wisely, and only spend on gear that will pay for itself in quality, efficiency, and better sales potential. Sometimes we have to improvise, overlap and use what we have. The only GAS we have goes into the tank!

The attaced image is indicative of my glamerous life of a commercial photographer! No majestic mountais or beautiful modls this week! Shot with 24-105. Made into a 80x`100 inch print for a trade show booth.

It might be reasonable to ask yourself whether the clients for whom you're doing the "volunteer event" images will ever actually see the difference in sharpness that you will be paying $$$ for. If you want it for yourself, then pony up the dough and enjoy your gear without looking back. If you're spending the $$$ just for the clients you volunteer for, I suggest you give yourself a thump in the forehead with the palm of your right hand and repeat this line "What was I thinking?". This is coming from a guy who owns and enjoys 7 Nikon lenses.