DAN Phillips Loc: Graysville, GA

Please excuse ignorance! What is MFT?

wdross Loc: Castle Rock, Colorado

Micro FourThirds

Cdouthitt Loc: Traverse City, MI

Shoot the 75 1.8 wide open...but even so, I’m doubting that’ll give enough separation without still needing to blur the background.

If you lived closer I’d let you try my 150 f2. That would likely do the trick, but then you’d be stuck at that focal length.

DannyKaye Loc: Sheffield now but soon moving to Blanzay

Your f/2.8 lens wide open should approach what you want but a wider aperture should make it easier because you gain some apparent DoF on a crop sensor. basically keep it wide open and raise ISO to get a useable shutter speed, you don't say what sports but if it is fast moving a higher shutter speed is more useful than low ISO. Don't get an f/4 lens it won't help.
Danny

Architect1776 Loc: In my mind

Stunning!!

wildweasel

I also believe a mid range zoom might be the answer, something like the 75-300.

ELNikkor

The 12-100 f4 you mention would be counter-productive to your goals, as you want wide apertures and longer focal length, not a shorter, slower lens. Did you set the 40-150 aperture priority at 2.8? That will give you the most blur-for-the-buck foreground and background. You'll also get the most blur at 150 with the subject as close as possible, (ie, not far away and cropped in in post.) If you get any other lens, it might be the 75-300, as that will allow you to fill the frame from farther out. Just be sure your aperture is wide-open to get the maximum isolation of your subject.

MrBob Loc: lookout Mtn. NE Alabama

Trav, if you want to Isolate the subject with an M43 lens try out a 75 1.8 as Gene has suggested... I just bought one to chase my dogs around. Acts like the Canon 135 and is a gorgeous lens.

dcampbell52 Loc: Clearwater Fl

I don't have any problem with DOF on my DX camera (Nikon D7100 and Nikon D7000 or my old Nikon D70s NOTE: ALL DX cameras). I generally use a 50mm, 18-70mm, 70-300, or an 80-400mm lens and put the camera on aperture priority or shoot manually using a wider (most wide open) f/stop... I don't let the f/stop go more than one or two clicks below wide open and focus on my subject. Usually the foreground and background drop out of focus leaving ONLY the subject. DOF IS DOF regardless of full frame or crop sensor.. However, DOF is wider /different on DX. Use the DOF app on the internet... it will show you the focus area for any lens on any camera.

http://www.dofmaster.com/dofjs.html
try this... I have it on my cell phone and on my computer at home.

mizzee Loc: Boston,Ma

I recently tried that same lens and you're right about the ungainly! In fact all my horizons were tilted because I had to hand hold and I wasn't used to the weight. I think the 75-300 might be a better choice. I own that one and it isn't ungainly.

TSHDGTL

For out of focus background the ratio between camera and subject and subject to background need to be high. Crop cameras require you to move back further to get the same composition which messes up this ratio. One alternative is to use a long zoom lens to compress the background.

camerapapi Loc: Miami, Fl.

"Unfortunately, that is a common issue with a camera with a smaller than full frame sensor. Crop sensor cameras will always give you a greater depth of field than a full frame."

This is not totally true. It will be very hard for anyone to see a difference in depth of field with both cameras set at f16 when photographing the same subject from the same distance. To blur the background, lets say in portraits, because of the increased magnification with a cropped sensor it will be necessary to come closer to the subject to blur more the background like done with a "full frame camera.
Panning is a good way to blur backgrounds using a shutter speed of around 1/30 sec. or so. I do not know how to blur the background in sports unless a large aperture is used with a tele and the background is somewhat distant from the subject.

I do not know how successful is the OP using a camera like the EM-10 Mk II that has only contrast detection AF to photograph sports. I would say the Olympus EM-1 Mk II would be a better choice. The 40-150 f2.8 Pro is an excellent lens from all I know about it but it is somewhat bulky and heavy. That was the reason I bought the cheap 40-150 f4-5.6 kit lens which is light, compact and has excellent image quality. The lens mount is plastic, nothing that bothers me and it has variable apertures like many other zooms so in low light its performance could not be optimal.
The Zuiko 12-100 f4 Pro is known to be also an excellent optics but I have no experience with it and cannot make any comments at this time.

Cdouthitt Loc: Traverse City, MI

Oh crap...I missed that he was shooting with an em10ii...I thought he said em1ii. Scratch my earlier thought about using the old 150f2...it would only work in manual focus mode...which doesn't work all that well when you're talking about moving objects.

lamiaceae Loc: San Luis Obispo County, CA

Get a FF camera, problem solved. Other than that, as others are explaining, careful choice of FL, Distances, Stops, and Expectations from the equipment. The things MFT could stand for. One I should not quote here.

TRAVLR38 Loc: CENTRAL PA

Thanks for your rapid reply. I am having trouble sending images. This is the first time I have tried to do this. The UHH program doesn't seem to want me to send more than one image at a time. No clue why, but I cannot select more than one. They would be raw anyway. I deleted most of my jpeg originals in LRCC after having made the edits I wanted. Trying to save space on hard drive.