Final Notes on Barrel Distortion and CA
This post concludes the first preliminary indoor and short distance WA converter lens test.
BARREL DISTORTION
The following image shows the barrel distortion of the four 0.8X lenses (Minolta ACW-100, Nikon WC-E80, Nikon WM-E80 and Olympus WCON-08B). It is clear that the WCON-08B is slightly better than the Minolta ACW-100, and both are better than the two Nikon’s. Of the two Nikon’s, the WC-E80 is better than the WM-E80. The latter has a very bad barrel distortion. This reminds me an interesting incident when I first took the WM-E80 on a trip to St. Louis last Spring. I position the magnificent arch in the upper right quarter in an image with portrait orientation and found out the top portion arch has a strange looking (i.e., the tip of the arch tilting to the left). I posted my image on the Nikon Talk board and everyone indicated that the WM-E80 is not that bad and that it is my skill that caused the problem. Well, people really did not want to admit problem of their equipment.

The following one shows the 0.7X group (i.e., Olympus WCON-07, Panasonic LW55, Raynox HD6600pro-55, and Sony VCL DH0758). In this group, the Raynox is the winner. This is followed by the Olympus WCON-07 and Panasonic LW55, with the Panasonic very slightly worse. The Sony does not look good here.

CHROMATIC ABERRATION (CA)
While in the first post CA was discussed, I intend to add one more piece of information here. The following is a 100% crop of the upper left corner of the 0.8X images. The focus is the high contrast area between the bookend and background. The contrast is not very high actually; however, the reflection makes the situation bad. Of these four, only the WCON-08B did not show fringing, and the Minolta ACW-100 is just slightly behind. Both Nikon’s show purple and greenish fringes with the WM-E80 worse than the WC-E80. Note also that the Minolta ACW-100 is sharper than the WCON-08B! In fact, both the Minolta ACW-100 0.8X and ACT-100 1.5X perform respectfully at corners.

The following shows the upper-right corner of the 0.7X lenses. The Panasonic LW55 is very clean. The WCON-07 is the worst with strong purple fringes between high contrast areas. Although the Sony and Raynox both show some purple and greenish fringes, IMO the Sony is slightly better.

SHORT SUMMARY
In this indoor short distance comparison, I believe the Panasonic LW55 is the winner of the four 0.7X lenses, and the Olympus WCON-08B and Minolta ACW-100 are the best two of the 0.8X group. However, the ACW-100 does show some very slight CA although not very significant; however, its off-center sharpness is the best.
Lastly, I have to point out that we should not use one set of images to judge the quality of a lens. This is the major reason that I always use multiple scenes each of which is designed to reveal one set of problems. The above scene works for lower contrast and short distance shooting. In the near future, I will add other scenes for other purposes (e.g., higher contrast, long shooting distance, moderate shooting distance, etc). It is very naïve to show a high contrast scene in which strong CA can be seen as a counter-example because shooting parameters are completely different. It is also very naïve to say one’s image is more “real life-like” than the others in terms of lens testing. As long as a scene can reveal the problems (YES, lens testing is for telling the problem rather than hiding them), it is a good scene to use, and this is not a “real” vs. “not real” issue. If a “real” scene does not reveal the problem in a test/comparison, it is not fair because that test simply hides the weakness of a lens.
I’d also like to point out that I only compare the lenses in hand. They are part of my collection because I use them regularity for my work (i.e., research, writing, leisure, etc). I did not have any intention to acquire a lens that I won’t use frequently. While other lenses may be available to me from my colleagues or friends, the period in which I could use these lenses may not match my working schedule. As a result, I could not compare these lenses. Hope you will understand this. It is neither a bias nor an aversion. It is simply that I have to use my $$$ wisely for my work.
CK
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Nikon Coolpix 950/990/995/2500/4500/5700, Panasonic FZ-10/FZ-30, and Canon A95 User Guides