You can get a new 7D for under $1000 these days, surely that's worth paying?
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Your typical dSLR AF system doesn't focus precisely with lenses wider than f2.8.False. The AF system is specified to a given level of precision - the f/5.6 lines are precise within one depth of focus at the lens' max aperture, the f/2.8 lines within one-third the depth of focus at the lens' max aperture. It doesn't matter whether the lens has an f/2.8 or an f/1.0 max aperture, the AF system will be precise to that degree relative to the max aperture of the lens. Note that precision is specified, not accuracy. Precision ≠ accuracy.
The DoF at apertures wider than f/2.8, especially with reasonably close subjects, is so thin that any misalignment in the AF system will be exposed - that's the accuracy part. That's why we have AFMA - to correct for the inaccuracy introduced by misalignment of the AF sensor with the image sensor. A properly microadjusted lens will be accurate, and precise within the limits stated above, i.e. the obtained focus will be distributed around the 'true' focus in a manner bounded within 1/3 or 1 depth of focus (probably not hard boundaries, but likely about 3σ, which is a standard tolerance in most processes).
However, manually focusing a lens wider than f/2.8 through the viewfinder with a stock focus screen is not accurate or precise, because the stock screen does not show the true DoF of a lens faster than ~f/2.8. The AF system will do a lot better (if properly adjusted).
...When you recompose, you change the angle and can change the distance to the subject which will throw of your focus if you are shooting really shallow. This focus system is not appealing at all. ...
...My questions for you all are:
1) What lenses do you own and why do you love/hate each of them?
2) How long have you been into photography?
3) Any random tips for a noob like myself?...
Well, I used this thread and some others to help me decide on this trio during the 20% refurb sale:
EF-S 17-55 f2.8
EF 85 f1.8
EF 70-200 f4 (non-IS, shooting kids sports outdoors in sunny Florida)
I know it doesn't sound very impressive against everyone's dream list that costs $10k+, but I'd say I did alright for $1.5k and got 95% of the performance those lists offered.
....In the case of lenses, they are reporting resolution as a peak measurement - the highest resolution measured at any location in the lens' FoV, at any aperture setting, and for zooms at any point in the focal range. Maybe the lens is crap wide open and crap through most of the zoom range - DxOMark's resolution score doesn't care....
....the real problem with the DxOMark scoring ....they make it far too easy for human nature to pounce on that number and say, "This one is the best."
To sum up, IMO, DxO's Measurements are valid and useful, their Scores are meaningless, and the inappropriate interpretation that many forum posters apply to their conflated scores is reprehensible.
...I am happy with my 5D3. However, I also agree Nikon has better sensor. ...
....So basically to get a true comparison I need to photograph one subject with both cameras but with the 40D zoom to 180% to get the same magnification to accurately compare?...