Sean Reid's observations on M mount lenses on the G1

[Martin S]

Just read the Sean Reid article where he noted some decreased resolution in the frame corners when a Leica M lens was used as compared to the results from the kit lens.

He ascribes the differences to the way that the peripheral sensor photo elements handle the off axis light rays for the kit vs M mount (film based) lenses.

Anyone else note these differences??

This would seem to reduce the applicability of the large number of M mount lenses.

Martin

 

[monza]

There is some mention in this thread:
http://forum.getdpi.com/forum/showthread.php?t=5450

Is this across the board with all M lenses or just wide angle?

 

[Bernard]

I don't think that resolution is a good reason for using adapted lenses on the G1.
The kit lens is really good. No adapted lens is going to give sharper results on that sensor.

Adapted lenses are great because they give you options.
I know that, with my 4/3 bodies, the Olympus 4/3 50 macro gives me one look, and a Zeiss 50 gives me a different look (and 50mm on a 4/3 zoom is something else again). I could spend hours in front of the computer trying to make one lens look like the other, or I just carry both and get the look I want right away.

To put it a different way, the fact that M lenses do not give the same results as the kit lens increases the applicability of M lenses. Why else would you bother mounting an M lens on a G1, if not to get a different look?

 

[Martin S]

Monza

I don't know if the focal length of the lens will change the resolution of the frame edge using M lenses. Sean only showed results from a 28 mm f 2.0 Leica Summicron.

Perhaps Sean can answer this directly??

Martin

 

[m3photo]

Re: Why else ...

Why else would you bother mounting an M lens on a G1, if not to get a different look?

... wider apertures = faster lens + better/different bokeh possibilities.

Just took along my C/V 50mm f/1.5 Nokton and shot where the kit lens at 45mm and f/5.6 wasn't what I was after.

 

[monza]

I am not a subscriber, so the only lens tested on the G1 was the 28?

It's interesting that people have been using M lenses on the G1 since December and this is the first time anyone has noticed this...

 

[peterv]

Monza

Perhaps Sean can answer this directly??

Martin

Hi Martin,

Sean Reid said over at LUF yesterday that he doesn't read GetDPI, unfortunately.

 

[peterv]

I mentioned the cornerproblems in a thread 10 days ago, but no one picked it up. Carl mentioned it too somewhere. People are beginning to wonder what's going on here.

Now to me, as I have practically zero knowledge about optics and sensor electronics, it's a riddle wrapped in a mystery inside an enigma.

All I can say is this:

- the corner problems are not just in 28 Cron shots, below you can see corner crops (f1,4 and f5,6) from a quick test I did with my pre asph 50 Lux. The IQ does seem to improve as the lens is stopped down. It's the same with the 28 Cron.

- I bought the 25 D Lux especially for my G1 and I'm very pleased with this lens. I like to keep it on my G1 all the time, but, the same kind of shot with tree branches in the corners of the frame show a lot of CA at f1,4 when opened uncorrected in Silkypix. When lens correction is applied in this raw converter things start to look a lot better. The same shot at f4.0 looks just fine.

- The first adapter I got from a well known German manufacturer was too short, and focussed way past infinity. The replacement they sent me two days ago will not focus past 10 meters, so back into the box it goes. I'm sure they will eventually get it right.

So, not being a technical guy, I'd say that from all this, it seems that the G1 sensor relies on post correction heavilly. Indeed the kit lens is very good, but than again, it's widest opening is f3,5...
The adapters, not just the one I mentioned, are another uncertainty. To what extend these adapter problems deteriorate the IQ I really don't know, and I'd very much like to find out.

All in all I'm a happy customer and I took 3300 shots with the G1 in one month. I like the ergonomics, and the value I got for my money. I'm hoping Leica or Olympus will come up with another µFT body that's a good addition to my G1. I would buy it in a heartbeat and get a complete camerasystem for fast documentary work.

Now I hope the text above and the samples below will help to further explore and get to the bottom if this.

Cheers, Peter

 

[Jonas]

(...)
- the corner problems are not just in 28 Cron shots, below you can see corner crops (f1,4 and f5,6) from a quick test I did with my pre asph 50 Lux. The IQ does seem to improve as the lens is stopped down. It's the same with the 28 Cron.

Hmm. I remember those images. To me and at least another poster that looks just like veiling flare. Have you now tried the same lens on an M8 and found it better at the borders?

(...)
- I bought the 25 D Lux especially for my G1 and I'm very pleased with this lens. I like to keep it on my G1 all the time, but, the same kind of shot with tree branches in the corners of the frame show a lot of CA at f1,4 when opened uncorrected in Silkypix. When lens correction is applied in this raw converter things start to look a lot better. The same shot at f4.0 looks just fine.

I have owned the Panasonic 25/1.4 and used it with my E-510. Corners and borders were not sharp. Stopping down helped but they never became critically sharp (far from it actually).

(...)
- The first adapter I got from a well known German manufacturer was too short, and focussed way past infinity. The replacement they sent me two days ago will not focus past 10 meters, so back into the box it goes. I'm sure they will eventually get it right.

So, not being a technical guy, I'd say that from all this, it seems that the G1 sensor relies on post correction heavilly. Indeed the kit lens is very good, but than again, it's widest opening is f3,5...
The adapters, not just the one I mentioned, are another uncertainty. To what extend these adapter problems deteriorate the IQ I really don't know, and I'd very much like to find out.

You are saying Novoflex screwed it up again? Oh oh.

Why should the adapter have any impact on image quality at all? I'm not that technical either but I would imagine a correctly made adapter with parallel "sides" has no impact at all on IQ. Thinking about it all a mechanical adapter does is to move the lens a bit away from the sensor placing the chunk of glass where the focusing mechanism can be used for focusing from MFD to infinity.

The rest is air and, possibly, reflections. Reflections wouldn't increase CA or make borders blurry though.

What I can think of is that the sensor needs the light to hit the pixel dwells in a bit more straight way (is that perpendicular?) than we (me, everybody?) have assumed. I don't kow how that works with a lens stopped down giving us just very good "sharpness" also at borders/corners.

I see no real reason to worry. I don't look for perfect borders shooting wide open. I want the borders and corners to be decently sharp when I have stopped down (read landscapes, architecture, documentary images).

Maybe some of us just expect too much from 30+ old Leica stuff? I remember Erwin Putz commenting on Voigtländer lenses (which he found to be bad compared to Leica lenses of course) saying they all were clearly better than 10 years old leica constructions. Whatever that tells us.

just my cents, /Jonas

 

[m3photo]

Cosina-Voigtländer Nokton 50mm f/1.5

Best example I can muster today: at f/1.5 - Handheld at 1/30th shot through glass and the in-focus edges seem OK to me.

 

[scho]

Re: Cosina-Voigtländer Nokton 50mm f/1.5

Best example I can muster today: at f/1.5 - Handheld at 1/30th shot through glass and the in-focus edges seem OK to me.

Hard to judge from a 3-D target like the coiled snake, but the lower right and left corners look a little weird.

 

[Ranger 9]

Sean Reid said over at LUF yesterday that he doesn't read GetDPI, unfortunately.

If he decides he wants to start, I think we should charge him $24.95 per year for a subscription. >:-0

 

[peterv]

If he decides he wants to start, I think we should charge him $24.95 per year for a subscription. >:-0

:ROTFL::ROTFL::ROTFL:

 

[monza]

Heh.

I remember those photos, but there was something said about them being taken through a car window...

I do not have an M adapter at the moment but I did test two lenses, a 20/3.5 Olympus Pen F lens and a 24/2.8 Nikkor AF, neither of which exhibited any corner distortions...both of these lenses are SLR lenses of course, not RF lenses, if that makes a difference...

 

[Ranger 9]

Just read the Sean Reid article where he noted some decreased resolution in the frame corners when a Leica M lens was used as compared to the results from the kit lens.

He ascribes the differences to the way that the peripheral sensor photo elements handle the off axis light rays for the kit vs M mount (film based) lenses.

Anyone else note these differences??

I think this article on the Four Thirds website gives a good insight into what Reid is said to have noted. The diagram in the "Enhancing the Linearity of Light" section seems significant.

The article argues that the Four Thirds standard gives a uniform spec for optimizing the design of the camera lenses, the design of the sensor and its microlenses, and the in-camera and post-processing software so they all work together as well as possible.

In view of that, it's not exactly surprising that a third-party, non-optimized lens might produce, um, non-optimized results.

It's too bad that the full Four Thirds spec is revealed only to member companies that have signed the nondisclosure agreement; otherwise we could have hours of fun trying to develop rules of thumb for deciding which third-party lenses will be the most Four Thirds-friendly and which won't.

Lacking that, though, we'll have to do it the old-fashioned way and rely on experience... which this would be a great place to share, of course!

 

[peterv]

To me and at least another poster that looks just like veiling flare

Hi Jonas, it may look like veiling glare , but the question is what is causing it? Would you say you're 100% sure it's not the adapter?
I know this 50 Lux I used certainly does not show veiling glare like that on my M's.

Maybe some of us just expect too much from 30+ old Leica stuff? /Jonas

Sean Reid did his tests with a relatively new Summicron 28 mm. So have I, and I think Carl too.

 

[peterv]

Heh.

I remember those photos, but there was something said about them being taken through a car window...

That's right. Two days later, after getting no further response, I decided to delete the sample photo's. Oh, well.

 

[Y.B.Hudson III]

soo...Peterv, did you ever do an articulate, re-pete-able lens test to illustrate your supposition?

 

[peterv]

Hi Y.B. I'm just asking questions. Don't do scientific tests, certainly not through car windows

 

[Martin S]

This initial post has certainly generated a lot of interest, and great responses.

I think that one of the causes of the apparent edge resolution "problems" is a simple law of optics. The light rays entering at the sensor periphery are too oblique to strike the sensor photosites with the same accuracy as the center photosites. This is basically the same argument that Olympus made for the original 4/3 concept.

The apparent better results from the "kit" lenses maybe related to either some design modification in the lens, or some post processing tricks that boost, and sharpen the peripheral sensor responses.

This may have cause some limitations on the M lens utilization on the G1, especially wide angle lenses at wide diaphragm openings. Unfortunately, this is exactly the type of lM, or CV lens that we would use.

Any thoughts.

Martin