Jock....I'll give you my thoughts.I can’t thank you enough Northstar, I will try Snapseed as you have recommended, sounds like it will suit my needs perfectly with my current kit, Microsoft Picture Manager does not have a “sharpening” tool and this is the only program I have used this far, just for cropping or increasing/decreasing colour, brightness etc.
With the sigma 150-500 at 500, it's just not a real sharp lens at 500, even at f8, decent but not great. But there are a couple things you could do to help get better focus and sharpness.
First, with faster moving subjects, I really like to shoot at twice the focal length....1/1000 in this case with your 500mm. You were at 1/640...so I think this will help. With the 500mm and flying birds, 1/1000 is your absolute minimum..IMO.
Second...learn to use a good editing tool to improve contrast, sharpness...etc. I did a two minute edit on my iPad to your first photo, just cropping, straightening, and sharpening....it helps. I used snapseed..it's free.
Good luck sir!
Original and the edit
I really appreciate your critique as I knew that the IQ errors were down to the dodgy user rather than the lens, I will increase my shutter speed next time I’m out, and would an increase to f10/12 help too? As in will more of the bird be in focus if I’m using spot metering??
Again, thanks for your help.
Jock...as Rienz wrote, f11 would give you several more feet of DOf and slightly better sharpness...BUT, you shouldn't bump up the ISO on the t2i past 800 or it will start getting noisy, so keep that in mind.
I posted a link to a handy online tool for learning about DOF at different settings. At f8 you have plenty of DOF if the birds are 70 meters away or more. At 70 meters( I'm guessing the distance based on looking at the photo) and 500mm f8, you have 6 meters of dof....that should be plenty of dof.
Also...if you haven't seen it, the digital picture has a lens sharpness comparison tool. Plug in your sigma at 500 and compare to other lenses.