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Old Feb 11, 2006, 12:23 AM   #1
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Started to think about my wide angle converter comparison recently. The first thing to do is to find scenes that can easily reveal the "problems" of each and every lens. This scene has to be somewhat weather independent so that I could reshoot some results at will. Yes, I could use lab equipment such as optical bench; but, the results may not be very reader friendly. As a result, shooting actual scenes is my favorite way. Please keep in mind that these scenes are not for artistic expression, they are chosen because they can reflect real shooting and at the same time can easily reveal problems of the lenses being tested. This is the first test run and may not represent what will follow on my comparison pages.



This scene is a section in the library of my university. I choose this scene because the subjects are virtually on a flat surface and full of little features. I did a white balance present and then set up my camera about 2 meters away. Since library illumination is not strong as usual, the aperture and shutter speed are f/5.6 (the middle one) and 1/8 sec. This is a slightly underexposed to make sure features on white surfaces can be seen for comparison. Unfortunately, I can only set the noise reduction to low rather than turning it off. Consequently, I do not know what the impact of NR on image sharpness is. Additionally, as usual, all shooting parameters are set to the lowest settings.



Converter lenses used include: Minolta ACW-100, Nikon WC-E80, Nikon WM-E80 and Olympus WCON-08B (the 0.8X group), and Olympus WCON-07, Panasonic LW55, Raynox HD6600pro-55 and Sony VCL DH0758 (the 0.7X group). The Nikon WM-E80, which is not discussed on my FZ-30 user guide page, is a single element and very light design (for Coolpix 8800). It does not have a usable thread for the FZ-30, and, hence it is hung over the FZ-30 lens. The WCON-07 uses a 55-62 step-up ring and a 62-55 thread converter to remove the center blur spot as described in my FZ-30 user guide.



The following shows the scene at 0.8X (by Minolta ACW-100) and 0.7X (by Panasonic LW55). In this post, I only looked at the center and lower-left corner marked by yellow rectangles.









*** 0.8X GROUP ***



Let us look at the 0.8X group first. The following has the four center crops from the 0.8X group. From these four crops, I would say they are very similar to each other with the WCON-08B slightly ahead of the Nikon WM-E80 and Minolta ACW-100. Surprisingly enough, the once well-known Nikon WC-E80 did not produce an image as crisp as the other three. However, I'd like to point out one important fact: like the TC-E15ED, the WC-E80 has a deeply recessed rear element. Whether this is an important factor is not known.









The following is the lower-left crops. It should be clear that the Minolta ACW-100 and WCON-08B take the lead. IMO, the ACW-100 is slightly better; however, it also produced a very slight touch of purple fringing. Blow up the crop to some degree and the purple fringes can be seen along the lower left corners of high contrast areas. The Nikon WM-E80 seems slightly better than the Nikon WC-E80, and the former has some greenish fringes while the latter has some purple fringes. These fringes are so thin that may not appear in prints unless the print size is unusually large.









*** 0.7X GROUP ***



The following shows the center crops of the four 0.7X wide angle lenses. None of these four is as good as the 0.8X lenses. The Raynox HD6600pro-55 seems to have lower contrast than the other three, and, as result, its result does not look as sharp as those of the other three. Of the other three, the Panasonic LW55 and Olympus WCON-07 are equally good, and both are very slightly better than the Sony DH0758.









The following is the lower-left portion. Clearly, the Panasonic LW55 is better than the other three. The LW55 did not show chromatic aberration even in 150% enlarged size. The Olympus WCON-07 is also sharp, in fact, maybe as good as the Panasonic LW55; however, some purple fringes can be seen along the left edges of bright areas. The Sony VCL DH0758 is not as sharp and has clear greenish fringes. The Raynox HD6600pro-55 has a soft edge which is worse than that of the Sony DH0758. This softness also amplifies its greenish fringes.









*** 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.









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.







*** LIGHT LOSS AT CENTER ***



By definition, adding a converter lens does not affect exposure value (i.e., EV) because the added converter lens changes the focal length and magnifies the entrance pupil by the same ratio. However, all glass elements will absorb and reflect some incoming light. High transmitting ratio glass elements and better multi-coating technology can reduce absorption and reflection, respectively. However, this light loss is still there.






To measure this light loss, I used the following setup. I open a large white window on a flat and good LCD monitor, and have a 1-degree spot meter pointing at the center of this large white area. Take five direct measures, mount a lens in front of the spot meter, and take five measures again. The difference between direct measure and the measure with a lens mounted is the light loss in EV. Since my spot meter is only accurate to 0.1 EV, the resolution of this difference is 0.1 EV.



Here are my measured results. All numbers are measured differences averaged and rounded/truncated to one digit after the decimal point.



*** 0.7X GROUP ***



Olympus WCON-07: 0.2 EV

Panasonic LW55: 0.1 EV

Raynox HD6600pro-55: 0.1 EV

Sony VCL DH0758: 0.1 EV



*** 0.8X GROUP ***



Minolta ACW-100: 0.1 EV

Nikon WC-E80: 0.1 EV

Nikon WM-E80: 0.1 EV

Olympus WCON-08B: 0.1 EV



Except for the Olympus WCON-07 that has a light loss of about 0.2 EV, all others have a light loss of around 0.1 EV. Since camera meters have 1/3 EV step, they perhaps could not recognize this 0.1 EV or 0.2 EV difference unless the original measure is at the border of 1/3 EV.



Note that I only measured the center portion. The difference between center and corner can vary from less than 1 EV to 2 EV depending on the lens. This can be visualized by shooting a uniform blue sky as shown on my FZ-30 user guide pages



*** 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 to tell the problems as well as good thingrather 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.



CK

http://www.cs.mtu.edu/~shene/DigiCam

Nikon Coolpix 950/990/995/2500/4500/5700, Panasonic FZ-10/FZ-30, and Canon A95 User Guides


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Old Feb 11, 2006, 1:00 AM   #2
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Thanks for sharing this useful information
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Old Feb 11, 2006, 3:39 PM   #3
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Yes, thanks a lot for the evaluation, Shene! Though it confirms that I own a soft image lens... (the HD6600).
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Old Feb 11, 2006, 6:36 PM   #4
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Good shots and information, as I am in the market for a WA lens for the FZ30. I really want to go with a 0.7x. I am probably going to still hold off a bit till I see some test pics of the Kodak Xenar 0.7x lens on the FZ30, since after reading about it on the FZ4/5 I was really impressed.


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Old Feb 18, 2006, 7:49 PM   #5
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Thank You Very Much Shene for your hard workand precise findings. I am about to purchace a WC. Your work has made my NEWBIE experience a whole lot easier towards my purchase.

HIGH 5!!!!!!
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Old Feb 19, 2006, 5:39 AM   #6
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Great, i just had made my mind up to by a raynox 6600, i'm confused now.

Great review:-)
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Old Feb 19, 2006, 8:47 AM   #7
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wadeatljust did some tests on the Kodak Xenar 0.7x lens and his finding show that at times the Kodak Xenar 0.7x lens does the same thing the Wcon-07 does, the center blur.
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Old Feb 19, 2006, 11:30 AM   #8
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The Kodak WA does do the centre blur on the one photo I saw, but the others (if they still were takes with lens on) did not show any "soft focus". Maybe I am blind or need a new monitor! :-)

There are fixes to the issue with the blur, using rings seems to be the most popular.
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Old Feb 19, 2006, 6:17 PM   #9
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polar905 wrote:
Quote:
There are fixes to the issue with the blur, using rings seems to be the most popular.
Yes, please see my FZ-30 user guide for possible solutions. They are discussed on the WCON-07 warning page.

CK

http://www.cs.mtu.edu/~shene/DigiCam

Nikon Coolpix 950/990/995/2500/4500/5700, Panasonic FZ-10/FZ-30, and Canon A95 User Guides




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Old Feb 20, 2006, 8:26 AM   #10
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I am hoping someone will post the off-set of the two rings, 55/62 step-up and 62/55 thread converter for the application of the WCON 07 to the FZ30!

TIA!!!!..................

Stan
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