i am busy with a new writeup about monitor calibration.

usually the jpeg (picture of alot black and white thingie) or software that show a series of black and white tweaking for monitor usually cover Contracts and Brightness.

Contrast shows details on Photo.
Brightness Shows "proper eV" on photo (important to calibrate as today most LCD are 'ultra bright' LED thing which make underexpose photo look overexpose.

only proper calibration tool like spyder will have advance calibration of RGB and TEMP. RGB is just a minor balancing. while temp is important, it give u the idea how blue or red is 5500k (but calibration standard target is 6500k due to RGB output, print out is CMYK) sometimes, u shot a normal 5500k photo, (general laptop are cool temp) but on ur lcd, it look blue (face arent cute red) so u might adjust the red slider till it look good on ur lcd. but on home pc (acer/samsung are warmer, HP dell are 6500k), it will turn out very red face.

so RGB/Temp show proper kelvin of ur photo.

(will continue after i finish the whole article and maybe will provide calibration service in future!....)

hmm,..u can see also picture from tamron/KM/sony 11-18.its share the same identical corner softness,share the same built and also the same hood.but from my point of view,it still acceptable.u can ask kysham for the sample.i know kysham also hiding the truth since he is not ready to upgred for 16-35Z!

but for the price tag 1.5k or below,u can get a good UWA lens for FF..isn't it good?