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

Guy Mancuso

Administrator, Instructor
Sorry if i confused the issue with the focus shift. Here is a thought and not sure it applies though. Does the G1 with the Raws in ACR and other programs correcting for distortion and such even if it does not know the lens on it. From these examples there certainly is falloff of sharpness but i wonder if the G1 is making general corrections in the raw on any lens if this could be the issue. Just a thought. Seems the wider the lens the worse the issue
 

Guy Mancuso

Administrator, Instructor
This is actually making some sense to me because the longer lenses the correction be applying if there is would have very little effect , on wide angles a much bigger effect. Maybe need to take these files into a program that does not make the corrections and see if the results are the same. That would tell us right off the bat . Than we need to get Pana. to be able to turn this OFF in the menu item.
 

robsteve

Subscriber
Guy:

It is the same problem I mentioned in the MFDB thread. The Leica M8 has angled micro lenses to correct the problems with the wides and the edges of the frame, the G1 doesn't.

We saw the same thing comparing the RD1 to the M8. Lenses that were crap on the RD-1 actually looked good on the M8.

Robert
 

peterv

New member
Interesting that there's a problem with your 90 Cron...
Hi Brian, I take that back. I'm sorry to cause more confusion here... Took another good look at the test I did with the 90 Cron, and cannot be sure it's not motion blur I'm seeing with the shots I took with the 90mm. Unfortunately I can't perform more tests since my adapter is back to the homeland for the second time.
 

peterv

New member
We saw the same thing comparing the RD1 to the M8. Lenses that were crap on the RD-1 actually looked good on the M8.

Robert
Hi Robert, good to see you here :)
I hope you can post some examples of the 'faulty' RD1 photos so we can compare. Thanks in advance, Peter
 

Guy Mancuso

Administrator, Instructor
Guy:

It is the same problem I mentioned in the MFDB thread. The Leica M8 has angled micro lenses to correct the problems with the wides and the edges of the frame, the G1 doesn't.

We saw the same thing comparing the RD1 to the M8. Lenses that were crap on the RD-1 actually looked good on the M8.

Robert
Robert micro lenses are only used to gather light in the corners and are not to increase or fix any sharpness issues in the corners. They just angle the light to illuminate the frame. Leica engineers will tell you the same thing. It does not fix any lens issues with regard to sharpness. Leica lenses do not have sharpness issue with a film Leica and will not with a crop M8 either it is to gather light.
 
R

Ranger 9

Guest
micro lenses are only used to gather light in the corners and are not to increase or fix any sharpness issues in the corners.
Yes, but they're still lenses, which means they're part of the total optical system. While I don't believe they're used to "fix" sharpness issues, it seems to me that they certainly could induce sharpness issues if they're poorly matched to the characteristics of the main camera lens.

What I suspect we're being shown in this situation is that the M8's sensor array, for all its flaws and compromises, is optimized about as well as is possible for the characteristics of M-mount lenses... while the G1's array is highly optimized for the characteristics of Micro Four Thirds lenses.

My interpretation is that for people who buy a G1 as a way of experimenting with the "looks" of a lot of different lenses, this difference in optimization simply will be another opportunity for interesting discoveries. For people who buy a G1 thinking it will serve as a budget M8 substitute, though, it's likely to produce some disappointments.
 

jklotz

New member
My interpretation is that for people who buy a G1 as a way of experimenting with the "looks" of a lot of different lenses, this difference in optimization simply will be another opportunity for interesting discoveries. For people who buy a G1 thinking it will serve as a budget M8 substitute, though, it's likely to produce some disappointments.
I agree, however, knowing that the wider ones will give me much more corner trouble than telephoto ones (with my lenses anyway), will save me from some disappointment down the road. Course' I'm not using a G1 for landscape or architectural work either. Horses for courses....
 

robsteve

Subscriber
Guy:

From the Dpreview review of the M8. It is item 2 that I am referring to. I guess it is called offset microlenses, not angled.

Robert

http://www.dpreview.com/reviews/leicam8/

Solving the corner vignetting problem

Because a rangefinder camera doesn't have a mirror box doesn't need to use retrofocus lenses, meaning they sit much closer to the film (or in this case the sensor). The problem with this comes with wide angle lenses (which are pretty much the main staple of the rangefinder camera). Towards the corner of the frame the angle of incidence of light coming from the rear of the lens is so severely off-perpendicular that they would not pass equally through the microlenses above the sensor leading to fairly strong vignetting. Even a modest wide angle lens at this kind of distance could produce a difference of a stop or two between the center of the frame and the edges using a standard CCD sensor.

Leica, obviously keen to solve this problem, took a three pronged approach with the M8:

1. Don't use a full frame sensor - at this time it would be cost prohibitive and too complex to produce a sensor which can cover the entire 36x24 mm frame and still work with rangefinder lenses. For this reason the M8's sensor measures 27x18 mm (or 1.33x crop).

2. Use offset microlenses - instead of placing all microlenses directly over the photodiode they are gradually offset as you get closer to the edge of the frame (see below).

3. Know which lens is being used and apply some software correction - all new M series lenses now carry a six-bit code which allows the M8 to identify which lens is used and (optionally) apply a 'final stage' software based vignetting correction (for RAW images the lens used is simply recorded, no change is made).
 
Yes, but they're still lenses, which means they're part of the total optical system. While I don't believe they're used to "fix" sharpness issues, it seems to me that they certainly could induce sharpness issues if they're poorly matched to the characteristics of the main camera lens.
....
While any single lens will give a more unsharp image if the light rays are at an angle with the optical axis, I can´t believe any such shortcoming of the microlenses would show up as unsharpness in the final image.

The reason is that each microlens serves a single pixel only, and there simply isn´t any way to see resolution within one pixel. Loss of illumination certainly, bleeding into adjacent pixels possibly, but resolution just cannot be affected by the microlenses; one pixel is the minimum detail in the image, period.

I´ve just returned from a week´s travel with the G1. and FWIW, before I went, I tested several Leica R and M lenses on a bookshelf (carefully checking parallelity, but no focus bracketing) wide open. I found both my Summicrons 35´s (old M one, and R) were quite bad, both Summicron 50´s (again, old M and R) good in the center, the M bad corners while the R was OK. Both my 90´s (Tele Elmarit M and Summicron R) were very good across the field.

I ended up taking the 50 R along. Sean´s review wasn´t posted by then, and no discussions had started, so I simply noted the results for my own use and threw out the test files...:confused: Now, when reading what´s going on, I´m more confused than anyone else...

While the 50 R may conceivably be more "telecentric" than the 50 M (to make room for the mirror), then why wasn´t the 35 R better? It clears that same mirror...

I don´t have the gear for measuring the position and size of the exit pupils (probably a relevant parameter), so I just give up...:eek:

I use those lenses that give me good pics in practice (and I use them for people, not bookshelves....:toocool:). But I´ll follow the discussions from ringside...
 

jlm

Workshop Member
so...
on the M8, both long and wide lenses show no sharpness falloff in the corners; wouldn't one then conclude that the M8 microlenses are not affecting corner sharpness?
Using the same lenses on a smaller G1 sensor is even less demanding, yet there is a falloff in sharpness with the wides, not the longs, compared to the kit lens.
Makes me suspect some sort of image processing in the G1 instead of microlenses
 
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