WA Converter Tests: [Preliminary Results 1]

Started Feb 9, 2006 | Discussions
Ching-Kuang Shene Veteran Member • Posts: 5,785
WA Converter Tests: [Preliminary Results 1]

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. I will address other issues in a later post.

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.

to be continued soon in this thread

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

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fbjon New Member • Posts: 6
Re: WA Converter Tests: [Preliminary Results 1]

Thanks so much, to me it certainly seems like you get what you pay for. My conclusion is that if I buy a converter, I'll go all the to the LW55 or not at all. The WCON07 seems like a very good lens as well (except for the small fringing in the corner) but then you might (probably?) have to fiddle with step rings as well.

I'm buying in Japan, and the price difference is only around 3500Y = 25EUR/30USD, so I'll stick with convenience, if I do.

A more pertinent question: how is the light fall-off in the corners on these, especially on the LW55?

fmoore Veteran Member • Posts: 7,669
Re: WA Converter Tests: [Preliminary Results 1]

Very well done, CK. Thanks for all the work you do. This seems to confirm the soft corners/edges others have noticed with the hd6600 on the fz30. The dcr6600 does better on the fz5 and one would expect the hd6600 (same lens) to do as well. The larger diameter of the fz30 lens is probably resulting in corner softness.

The ca with the wcon07 is also a little worrisome. It would be nice to see how the 55mm Kodak-Schnieder .7x compares.
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btb New Member • Posts: 17
Re: WA Converter Tests: [Preliminary Results 1]

Really useful info!... Thanks a lot : - )

MightyMike Forum Pro • Posts: 38,691
Re: WA Converter Tests: [Preliminary Results 1]

hmmm looks liek the 6600 doesn't perform as well as the others... this low contrast issue... is that due to the coating on the glass? if so is it easily fixed by bumping up the contrast in PP'ing ?
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yokes Senior Member • Posts: 1,077
Re: WA Converter Tests: [Preliminary Results 1]

Great test. Thanks!

I recently got a WCON-08E for my FZ30.. looks like it was a good purchase.

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Mejnor Regular Member • Posts: 411
Re: WA Converter Tests: [Preliminary Results 1]

Hello Mike,

As it is shown, all the 0.8X are better than the 0.7X.

Only 0.1X difference

Maybe all the 0.7X are better than the 0.66X

Mejnor

MightyMike wrote:

hmmm looks liek the 6600 doesn't perform as well as the others...
this low contrast issue... is that due to the coating on the glass?
if so is it easily fixed by bumping up the contrast in PP'ing ?
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Mike from Canada

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Rossuziers
Rossuziers Forum Pro • Posts: 12,855
CK Ya really should've

Run this by that guy over on the Sony forum 1st... Don't ya think??? LOL {j/k}
All I gotta say is 2 things...

  1. 1) It's really too bad the Pani adapters are so much more expensive or they'd be selling like no tomorrow...

  2. 2) And thanks CK

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OP Ching-Kuang Shene Veteran Member • Posts: 5,785
Re: WA Converter Tests: [Preliminary Results 1]

fbjon wrote:

A more pertinent question: how is the light fall-off in the corners
on these, especially on the LW55?

Light fall-off of LW55 is fairly typical among WA converter lenses, not significantly better or worse than other 0.7X lenses. It is a surprise that Panasonic's LW55 performs nicely, unlike the LT55 which is not so great given its high price.

CK

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OP Ching-Kuang Shene Veteran Member • Posts: 5,785
Re: WA Converter Tests: [Preliminary Results 1]

fmoore wrote:

The ca with the wcon07 is also a little worrisome. It would be
nice to see how the 55mm Kodak-Schnieder .7x compares.

I saw the CA with the WCON-07 ever since I mounted it on many digicams, Nikon 5700, Minolta A1, and FZ-10 just name a few. I expect the situation would be worse if contrast is higher, say in day light. The Raynox HD6600pro-55 has a similar characterstic.

Oh, Fred, don't push me to get a Kodak-Schneider 0.7X. Otherwise, my wallet will get thinner too soon because I just purchased a Sony 0.8X and 1.7X for my R1. :0(

CK

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genece Forum Pro • Posts: 15,435
Re: CK Ya really should've

I keep seaching for a decent WA lens and I am begining I should have just stayed with the first one I had... the DCR720....it was not perfect but nothing else is either and I think it was 40 bucks.
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------------------------------------------------------------
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Rossuziers
Rossuziers Forum Pro • Posts: 12,855
How do ya think I feel...

I'm lookin to get a single W/A adapter to do double duty on both the Fz30 & Oly 8080..

My only hope as far as I can tell is the Wcon 08D with 62mm treads for the E10/20 but noone's doing tests on either cam with it & the 8080;s not condusive to such a heavy piece screwwed directly to it.... And I'm really not in the mood to get a tube for the 8080... The 08 is actually no better on the Fz30 than the 8080 naked.. The 07 would be the ultimate giving my 24mm on the 30 & 19mm on the 8080 but I don't know if there's a 07 that's any good on the 8080....
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rsrascal Veteran Member • Posts: 3,014
Hey Gene, Thanks to the recent tip....

from bob fel, I picked up one of the WCON-08's on ebay (brand new in the box), for $59. plus shipping. I'm totally impressed with it for the price. I don't know the difference in the 08 or 08E for sure but if these show up again at that price, I'd go for it. According to Bob, the only difference is a regional designation.
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bob fel Regular Member • Posts: 367
Re: WA Converter Tests: [Preliminary Results 1]

Dr. Shene

This is said with all due respect,because i do respect your work,but are you going to test a wcon-08(europe designation) or the wcon-08e(american designation)same lens. I know that you have an adversion to it but it seems that people who buy it seem to like it.
thank you
bobf

oldschool68 Forum Member • Posts: 64
Interested in the kodak/schneider, too.

Your WA test won't be complete without it.:-)

llife Contributing Member • Posts: 853
Very [Preliminary Results 1] better results

I think your test are flawed I find lots of CA on the WCON08B and little to none on the WCON07 and very poor edge results on the HD6600.

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OP Ching-Kuang Shene Veteran Member • Posts: 5,785
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.

CK
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OP Ching-Kuang Shene Veteran Member • Posts: 5,785
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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mlanders Junior Member • Posts: 36
Re: Final Notes on Barrel Distortion and CA

Thanks for the superbe Testpictures - Really great!

One Question:
Whats about CAs and Picture Quality if you zoom in on or two steps.

In the following test the Picture-Quality of Raynox is going to be much more better if one step is zoomed in.

So from the end-result it should be the same quality in sharpness and picture measures like when i use a 0.8 Converter.

Here the link:
http://www.i-port24.com/G-Photo/

Best Regards
Michael

OP Ching-Kuang Shene Veteran Member • Posts: 5,785
Re: Final Notes on Barrel Distortion and CA

Michael,

Whats about CAs and Picture Quality if you zoom in on or two steps.

The image quality, when the camera lens is zoomed in a little, depends on so many factors, the most important one being the optical formula of the camera lens and converter lens. Some WA lenses can be used with good image quality when the camera lens is zoomed in even at 12X, while some others would give very bad results even at 2X. A good example is the Olympus WCON-07. Its image quality deteriorates fast passing 1X. This happens to all cameras that I have (none of them being an Oly). On the other hand, the Sony VCL DH1758 still is acceptable even at 12X. The difference comes from the optical formulae of the two lenses.

Zooming the lens to 2X (i.e., 70mm) is never a concern of my test/comparison because I believe a simple fact: more glass on a lens means worse image quality. My FZ-30 user guide has a demonstration with tele converters; but, the same applies to WA as well. If the lens is at 70mm (i.e., 2X), the combined focal length would be 46.2mm if a Raynox HD6600pro-55 is mounted. Since this 46.2mm is within the coverage of the camera lens, why bother using a converter? As a result, most WA converters are designed to be used at the widest end.

On the other hand, to yield 28mm with a Raynox HD6600pro-55 mounted on a FZ-30, it is equivalent to cropping the 23.1mm image a little as the 23.1mm image circle is the maximum the camera lens can see. So, zooming the camera lens in a little to 42.4mm means crop the image image delivered by the Raynox. However, one factor will affect the image quality: the HD6600pro-55 has a blurred border much larger than the camera lens at 42.4mm can cut, and, consequently, some blurred area still remain. So, I would not believe (although I did not do any direct comparison) zooming to a 28mm equivalent focal length with the Raynox would deliver result any better images than a 0.8X WA can do. Of course, the image quality actually depends on the camera being used. My point is based on FZ-10, FZ-30, Nikon 5700 and 8800.

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

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