Lens Test 3
I decided that I couldn't live with the additional warming and hence brought my lens back to my local camera retailer (Cathay Photo Singapore) who sold me the lens. They examined the lens and suggested that the warmer tone was likely due to the lens coating itself which are different between batches at the Canon manufacturing plants. In the end, they offered to change my lens just this once and that I would have to go back to Canon personally if I still weren't satisfied. I thought that was a pretty reasonable deal and so agreed (anyway, Canon's location is at most 5 minutes drive from my work place). In choosing the second EF28-135 lens, I made doubly sure that I also looked carefully at the lens coating for any signs of it being yellowish, hence signs of it being possibly warmer. That weekend, I set about shooting my third set of tests to check for sharpness (with/without IS), contrast and especially any obvious tonal differences.

• Outdoor shots (P mode and handheld except where mentioned otherwise) with a styrofoam board and various printed paper, colourful newsletters and a grey card
  (Roll 3- FujiChrome Velvia)

  Frame	Focal (mm)	TV	AV	IS	Remarks	Click On Thumbnail
  1	28	1/125	7.1	ON	with hood & UV
  2	35	1/125	7.1	ON	"
  3	50	1/125	7.1	ON	"
  4	100	1/160	7.1	ON	"
  5	135	1/160	5.6	ON	"
  6	28	1/125	7.1	ON	with hood & NO UV
  7	35	1/125	7.1	ON	"
  8	50	1/60	9	ON	"
  9	100	1/80	8	ON	"
  10	135	1/60	10	ON	"
  11	50	1/80	9	-	EF 50 f/1.8 MkII with hood & NO UV
  12	50	1/160	6.3	-	EF 50 f/1.8 MkII with hood & UV
  13	50	1/10	22	-	EF 50 f/1.8 MkII with hood, UV, tripod & remote shutter release TC-80N3
  14	50	1/6	29	ON	with hood, UV, tripod & remote shutter release TC-80N3
  15	50	1/6	29	OFF	"
  16	50	1/13	20	OFF	"
  17	50	1/8	29	ON	with hood & UV
  18	50	1/4	36	ON	with hood & UV, leaning against pillar

• Random subjects both outdoors and indoors (P mode and handheld except where mentioned otherwise) (Roll 3 - FujiChrome Velvia)

  Frame	Focal (mm)	TV	AV	IS	Remarks	Click On Thumbnail
  20	135	1/6	36	ON	AV mode with hood & UV, left elbow on ledge
  22	85	2.5	5.6	ON	with hood, UV, tripod & remote shutter release TC-80N3, kitchen light ON
  23	85	2.5	5.6	OFF	"
  24	100	1/60	5.6	ON	with hood, UV and flash
  25	100	1/60	5.6	ON	"
  26	100	1/60	5.6	ON	"
  27	135	1/60	5.6	ON	"
  28	135	1/60	5.6	ON	"
  30	30	1/15	10	ON	with hood & UV
  31	90	1/15	18	ON	"
  33	45	1/10	5.6	ON	Shot through glass window with hood & UV, focus on nearer building
  34	45	1/10	5.6	ON	Shot through glass window with hood & UV, focus on further building
  36	135	1/8	16	ON	with hood & UV, leaning against wall

This time, while the results showed acceptable sharpness (see the next set of tests for an enlarged photo comparison), contrast and no obvious tonal differences, I had yet another shock awaiting me - significant barrel distortion at 28mm. Pincushion distortion at longer focal lengths was also visible but was slight. While I understood that some form of distortion is usually present in zoom lens, I felt uncomfortable that so much barrel distortion was visible.