Contax G to micro-4/3 adapter available

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Archive 2009 · Contax G to micro-4/3 adapter available

KOJI
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p.2 #1 · Contax G to micro-4/3 adapter available

Lotusm50
......

What these samples do show from the center crops, however, is how sharp the 21mm Biogon is, particularly in comparison to the CV28 Ultron (both wide open, but f1.9 vs. f2.8).

I shot CV Ultron 28/1.9 @ f2 since I knew it is a bit soft @ f1.9, otherwise I agree with your statement above. I did test with CV-SWH 15/4.5 and CV-Nokton 35/1.2, they gave us
much the same results. I wonder how G-Planar 35/2 performs on GF1, I love this lens somehow even though its wide open performance is not stellar.

Nov 04, 2009 at 03:23 PM

Jonas B
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p.2 #2 · Contax G to micro-4/3 adapter available

Thank you for getting back on the topic KOJI.
Your results are well in line with earlier discussions from another board with a more active µ4/3 section. There is an obvious difference between the CV28/2 and the older CV28/1.9 (the later having been reported earlier as "no corner smear").

While not being super sharp the little Panny 20/1.7 seem to be quite an achievement. During the time between announcement and materializing I was afraid Panasonic had promised more than they could keep.

You saved me from ordering the adapter (I think, the Zeiss G 45/2 still may work very well on a G/GH1 camera). I'm sorry you didn't get better results. It would have been wonderful if the small Zeiss lenses could have been used with confidence.

Nov 04, 2009 at 05:47 PM

Sam N
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p.2 #3 · Contax G to micro-4/3 adapter available

Lotusm50 wrote:
KOJI wrote:
It now looks like Leica/Kodak pulled off quite a feat with the full frame sensor in the M9. It seems to handle this sort of thing a lot better.

The R-D1 works pretty well in the corners with the CV 15/4.5, 21/4, and 28/1.9. Sure it has bigger pixels, but they're also further away from the center of the lens. The bigger problem is light falloff with the 15 and 21, but even that isn't a big deal.

15mm on R-D1:

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And another one:

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full size

Nov 04, 2009 at 06:21 PM

Lotusm50
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p.2 #4 · Contax G to micro-4/3 adapter available

Hmm. So if the Leica can do it and the Epson RD-1 can do it, what's the problem with the sensor in the Panny G1, and presumably the Oly E-P1??

Nov 04, 2009 at 08:50 PM

Spyro P.
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p.2 #5 · Contax G to micro-4/3 adapter available

Lotusm50 wrote:
Hmm. So if the Leica can do it and the Epson RD-1 can do it, what's the problem with the sensor in the Panny G1, and presumably the Oly E-P1??

They are CMOS sensors.

Nov 04, 2009 at 10:40 PM

Sam N
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p.2 #6 · Contax G to micro-4/3 adapter available

Well, that's a difference, but not necessarily the problem...

That said, the R-D1 doesn't have fancy offset microlenses like the M8 (and presumably M9), but a plain old D100 sensor (which is pretty damn impressive).

Then again, the 12mp M43 cameras have a 5MP/cm^2 density while the R-D1 has a 1.6MP/cm^2 density.... the R-D1 pixels are over TRIPLE the size.

Nov 04, 2009 at 11:06 PM

Jonas B
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p.2 #7 · Contax G to micro-4/3 adapter available

And the post by the suede, and mentioned earlier: Panasonic and Olympus stack a supersonic filter on top of the AA and UV thingies in there, and the microlenses are probably not positioned in an "offset" manner.

What I would like to see is a good 10-12mm prime for the µ4/3 system. It doesn't need to be very fast but it should perform as well as the ZD7-14. Then the system would have decent primes; a wide, a normal and a short tele (yes, that's my needs).

Nov 04, 2009 at 11:18 PM

Jonas B
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p.2 #8 · Contax G to micro-4/3 adapter available

...and right now I read that Olympus will release a µ4/3 9-18mm lens to be for sale sometime before next summer. OK then. It's not a prime, it's not fast but it sure look small and neat. BJP

(Sorry for going off topic)

Nov 04, 2009 at 11:31 PM

Alex
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p.2 #9 · Contax G to micro-4/3 adapter available

The edge smearing is the result of spherical aberrations introduced by glass layers above the sensor (AA/IR filters and dust shaker). A simple explanation and illustrations of this effect could be found in the pdf from this link http://tinyurl.com/ydqsz2s. This pdf explains why Biogon 38mm is not recommended by Hasselblad for the use with digital backs.

The amount of the smearing depends on the distance of the lens exit pupil from the sensor. For the symmetrical lenses (and many RF lenses are symmitrical) this distance is simply the focal length. More generally, this distance could be calculated as the focal lengths multiplied by the exit pupil diameter and divided by the entrance pupil diameter. These diameters could be measured just be looking through the lens from both ends. Zeiss used to publish this data, so they are available for all Contax G lenses.

This distance should be compared to the frame diagonal which is 22.5 mm for m4/3. It is not very clear what is the good value for this ratio. As a reference point I included the data for Olympus 17mm which is the only m4/3 lens I own. It would be interesting to see the data for other lenses.
Lens Distance Ratio
Biogon 2.8/21 22.4mm 1
Biogon 2.8/28 26.6mm 1.18
Planar 2/35 51.6mm 2.29
Planar 2/45 53.1mm 2.36
Olympus 2.8/17 35mm 1.6

The 35mm and 45mm are in good shape. The numbers for the wide angle lenses are not promising.

We should expect that in practice we may see deviation from this theory. For example, a certain lens might have residual aberration which have the opposite sign and, at least partially, cancel the ill effect of the filter layers. In fact, I wouldn't dismiss the possibility that the m4/3 lenses are designed to have such residual aberrations.

Alex

Nov 05, 2009 at 02:29 AM

CVickery
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p.2 #10 · Contax G to micro-4/3 adapter available

I think Alex is onto something here. I had been assuming that the edge smearing issue was primarily an issue with the wide Leica M mount lenses and was caused by the lens' rear element being so close to the sensor. However, using Alex's approach above, this can be extended to adapted SLR lenses. I have the Oly 21/2 and have used it a bit on my E-P1 via a EOS adapter. I hadn't done any tests on the lens, but I worked out the ratio as Alex outlines (based on a block diagram since I don't have the lens in front of me). The Oly 21/2 ends up with a value of ~.5 which would indicate an edge smearing issue. As I said I haven't tested the lens...brick walls are in short supply

... but I did find this one shot that looks suspiciously like smearing.

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Apologies for the bad photography.

Nov 05, 2009 at 10:42 PM

Sam N
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p.2 #11 · Contax G to micro-4/3 adapter available

How could an SLR lens have an exit pupil closer to the sensor than the flangeback distance of the system it's from?

The value for the 21/2 should be more than 1, not less than 1. In fact, the flangeback for the OM system is 46mm, so the ratio can't be less than 2.1 for any of the lenses.

Nov 05, 2009 at 11:15 PM

CVickery
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p.2 #12 · Contax G to micro-4/3 adapter available

My mistake. I erroneously assumed that the entrance and exit pupil diameters would the diameters of the elements. A little more research would have given me the correct answer, and obviously you need to actually have the lens in your hands to measure them. The 21/2 has an exit pupil diameter of ~21mm an entrance pupil diameter of ~10mm. This computes to a ratio of 1.96 so any edge issues in my shot can probably be chalked up to bad technique.

I should note that using these diameters give a distance to the sensor of 44mm, which seems about right since the rear element seems to be about even with the surface of the EF adapter that's attached.

Nov 06, 2009 at 12:47 AM

Jonas B
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p.2 #13 · Contax G to micro-4/3 adapter available

Alex, thank you. Now let's see if theory and practise is the same in this case. Like CVickery I think you are on the right track. Maybe the exact numbers need to be adjusted but it all sounds plausible to me. Well, most complicated stuff do that as I only understand half of it. But here it also fits well with my experience.

Nov 06, 2009 at 12:56 AM

Alex
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p.2 #14 · Contax G to micro-4/3 adapter available

Jonas,
The exit pupil is the lens aperture as it appears from the back side of the lens. For all practical purposes the position of the exit pupil relative the focal plane determines the angle of the light when it strikes the sensor.

The procedure to determine this position is actually quite easy. You look through the back of the lens and measure the diameter of aperture as it appears from the back side (closing the aperture a little may help to identify the boundary). It is the diameter of the exit pupil. The same measurement from the front side will give you the diameter of the entrance pupil (don't change the aperture between measurements

). You divide the exit pupil by the entry pupil and get the pupil magnification (typically it is >1). You multiply the focal length by this number and get the distance between the focal plane and the exit pupil.

You mentioned two CV 28 which behave differently. If you have access to these lenses it would be interesting to get the numbers. In fact it would be interesting to get numbers for all widish RF lenses.

Alex

Nov 06, 2009 at 01:20 AM

Jonas B
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p.2 #15 · Contax G to micro-4/3 adapter available

Thanks again Alex. I think I understood how to measure the pupil sizes. What I don't understand exactly is how the limit is calculated. But it doesn't matter a lot - I just like that you presented a possible, probably, working model for how to estimate the lens' functionality in this case.

Unfortunately I don't have any of the lenses. I returned the CV28/2 after having seen the result I posted at page 1. KOJI posted a sample from the CV28/1.9 (a link) at page 1 as well. There clearly is a difference and yes, it would be interesting to learn about the entrance and exit pupils for a comparison. Maybe some friendly soul over at a rangerfinder forum could help with this?

Nov 06, 2009 at 02:25 AM

Jonas B
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p.2 #16 · Contax G to micro-4/3 adapter available

Here is another WA lens good for use with the µ4/3 cameras. I read about it earlier but wasn't sure exactly which lens it was. Then this thread popped up over at DPR yesterday, about the CV 12mm Heliar.

Nov 07, 2009 at 09:25 PM

CVickery
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p.2 #17 · Contax G to micro-4/3 adapter available

It looks like another adapter will be available shortly as well based on this thread. It's nice to have a choice and this one sounds interesting.
http://forum.getdpi.com/forum/showthread.php?t=11575

Nov 08, 2009 at 04:30 AM

Kingfishphoto
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p.2 #18 · Contax G to micro-4/3 adapter available

How does one focus the Contax G lenses on an alternative body? I remember all my G lenses were AF only,no manual focus rimg.

Nov 12, 2009 at 01:44 PM

mawz
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p.2 #19 · Contax G to micro-4/3 adapter available

Kingfishphoto wrote:
How does one focus the Contax G lenses on an alternative body? I remember all my G lenses were AF only,no manual focus rimg.

There's two ways.

The m43 adapters have a focusing wheel on them to drive the lens's focusing gear.

The M conversions install the optical unit in a new RF-coupled focusing helical complete with focus ring.

Nov 12, 2009 at 02:43 PM

Kingfishphoto
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p.2 #20 · Contax G to micro-4/3 adapter available

mawz wrote:
Kingfishphoto wrote:
How does one focus the Contax G lenses on an alternative body? I remember all my G lenses were AF only,no manual focus rimg.

There's two ways.

The m43 adapters have a focusing wheel on them to drive the lens's focusing gear.

The M conversions install the optical unit in a new RF-coupled focusing helical complete with focus ring.
Hi Thanks.
The latterof the two seems maybe on the expensive side-so to speak?

Nov 13, 2009 at 12:11 AM

mawz
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p.2 #21 · Contax G to micro-4/3 adapter available

Kingfishphoto wrote:
mawz wrote:
Kingfishphoto wrote:
How does one focus the Contax G lenses on an alternative body? I remember all my G lenses were AF only,no manual focus rimg.

There's two ways.

The m43 adapters have a focusing wheel on them to drive the lens's focusing gear.

The M conversions install the optical unit in a new RF-coupled focusing helical complete with focus ring.
Hi Thanks.
The latterof the two seems maybe on the expensive side-so to speak?

Expensive? yes. Cheaper than buying a new (and inferior) Leica 21 Elmarit? Yes. Transplanting the optical group was mostly done for 21 Distagon conversions because it is to this day arguably the single best lens at its focal length ever (Yes, it does outperform the ZM version).

Nov 13, 2009 at 01:41 AM

fotoking
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p.2 #22 · Contax G to micro-4/3 adapter available

I bought a couple of lens from KEH for about $150 each, really nice images produced on my m43 camera. I purchased couple of adapters from Amazon.com. Pro-grade adapter offered by Fotodiox, I am a happy man now.

Nov 16, 2009 at 11:36 PM

Alex
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p.2 #23 · Contax G to micro-4/3 adapter available

I got a jinfinace adapter. Adapter is well made and fits my E-P1 perfectly.

The lens lock is a bit quirky. After some trials I figured out a working technique: a) close down the lens aperture, b) stick your finger as close to the lens as you can and push the release button. The little piece of metal which locks the lens is very sharp and sheds small bronze particles into the camera. The long term solution would be to have an adapter for each lens.

Initially the operation of the focusing wheel was very stiff. A drop of WD-40 resolved the problem. Ergonomics of the focusing is far from perfect. The small wheel is hidden in a very narrow gap between the body and the black bulge on the lens. There are only a couple of hand positions when you can actually reach the wheel. The movement are not very smooth either. It works, it makes possible to focus with good precision, but it is not for manual focusing snobs. I think that a bigger wheel would've been much better.

It all may sound very critical, but in fact I'm quite happy that this solution exists. After I tried the adapter with a 45mm I ordered a 28mm and a 90mm.

The 45mm is very good. It is quite sharp wide open and gets better when stopped down. I had a chance to use it in our local park. The pictures could be found in http://tinyurl.com/yeaplxr (it was quite dark and most of them are wide open). Here is one wide open example

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The 28mm needed the "ears" trimming. They are just plastic - very easy job (don't let the debris to get into the lens). After this the lens mounts and focuses without problem.

I received this lens yesterday and with today's weather didn't have chance to use it. But I did a quick comparison to my CY 28/2.8. I set up two shots with both lenses - one shot with the object in the middle of the frame and another with the same object in the corner. Each time I focused on the object. All shots were developed in ACR - no noise reduction, sharpening amount 50 radius 1. The gallery of the test shots is here http://tinyurl.com/yzvpf44 (I really should've cleaned this table

). Below are 200% crops

Biogon 28 center

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Distagon 28 center

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Biogon 28 corner

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Distagon 28 corner

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At f/2.8 the Distagon is better in the center and in the corner. The Biogon improves when stopped down and gets marginally better at f/8. This behavior is confirmed by old photodo numbers. The Biogon appears to have some vignetting which didn't quite disappear even at f/8.

Alex

Dec 06, 2009 at 02:14 AM

Lotusm50
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p.2 #24 · Contax G to micro-4/3 adapter available

Alex wrote:
At f/2.8 the Distagon is better in the center and in the corner. The Biogon improves when stopped down and gets marginally better at f/8. This behavior is confirmed by old photodo numbers. The Biogon appears to have some vignetting which didn't quite disappear even at f/8.

That must be a function of the sensor. I've owned both lenses. On film, the 28 Biogon is noticeably sharper overall than the Distagon -- particularly in the corner of a 4/3rds sensor. With respect to vignetting -- the two lenses are actually quite similar wide open and stopped down. You should not notice a difference in vignetting between these 2 lenses at the corner of a 4/3'rds sensor if there wasn't sensor-related vignetting due to it's inability to handle the angle of the light from the Biogon.

In the film days, for me at least, the Biogon on the Contax G2 was the clear choice over the Distagon on an RTS.

Dec 06, 2009 at 02:49 AM

Alex
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p.2 #25 · Contax G to micro-4/3 adapter available

Lotus, you are right - it is a function of the sensor. More precisely, the layers above the sensor introduce some field curvature which deteriorates the corner sharpness.

Today in good light I made more tests with distant objects. The corner performance of this lens on my Olympus E-P1 is pathetic. At f/8 it is worse than my Distagon at f/2.8. Below is the corner crop. Full images are at http://tinyurl.com/yzvpf44.

It is a pity because I had really high hopes for this lens. Other than performance, it is a perfect fit for E-P1.

Alex

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Dec 06, 2009 at 08:36 PM


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