MFD on 70-200 F4L IS (+1.4TC & vs 70-300L)

General thoughts:

• Remember that for portraits, resolution is not nearly as important as good color rendition and bokeh.
• The max magnification of the 70-200 f/4 is a respectable .21x (so we're talking a 7cm-sized object to fill the frame), so its not as if you'll be at MFD for portraits either.
• While teleconverters will increase the max magnification of the lens, they don't change the minimum focus distance. For human-sized subjects, it would be the same as zooming in to 100mm f/5.6 and stepping back.
• Given the shutter speeds used for daytime motorsports photos with motion blur, you end up using f/8 - f/13 apertures ... at which point all lenses look great. Other than focal length, I can't tell the difference between the photos I took with the 55-250 and the rented 100-400 at the USGP this last year, they're all very sharp when processed properly. (I did add in some local contrast enhancement in DxO to bring out details.)
• For grandstand photos, you often want an insane amount of reach, but if you're at all near the corner (we were very close to turn 12), 100mm or even 70mm is too long. I was on the short end of my 55-250 for those shots all day.
• Abeam of the cars in daylight, the AF of the 55-250 on either a 450D or 500D was more than fast enough, even for the ridiculous acceleration and deceleration of the F1 cars. Head-on at closer range, ring USM becomes necessary, but those are wide-angle shots as well.
• For 1-2 races a year, it is FAR more cost-effective to rent a long tele zoom than buy one. My normal telephoto zoom remains the 55-250 (and I feel no need for something better).

My general thoughts are actually to not try to solve the portrait problem with a telephoto zoom on a crop camera, unless you get the Sigma 50-150 OS or a 55-250 ... 70-100 mm is great for outdoor or large room portraits on a crop body, but you need a fast 40-50mm lens for anything in a normal-sized room. The build quality may drive you nuts, but the nifty fifty still does great work at f/2.2-2.5 for this kind of stuff on the mega-cheap, and the 50mm f/1.4 is nothing to sneeze at and is still very reasonable compared to the other lenses we're discussing.

As for your telephoto zoom choice, I honestly don't know whether to tell you to just get a 55-250 and see if does the job or if you need a 100-400 ... it all depends on how much telephoto you need and how often. I am betting that a simple 55-250 or the 70-200 f/4 IS will do 90% of what you need. The 55-250 is actually pretty sharp at the short end and is f/4 there as well. The color rendition of the 70-200 f/4 is really really nice though.

No EXIF data from Facebook, but here are my USGP photos. Basically anything that shows multiple cars in T12 is the 55-250 in the 55-70mm range, the rest is the 100-400. There are some UWA shots mixed in (Tamron 10-24 in our case) and a few with our RX100 as well, but those aren't the car shots.

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