mFT Lens MTF Charts posted

MayaTlab said:

MayaTlab wrote:
The Voigtlander 40mm f2 for Nikon, for example.

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You suggest scaling everything to 50%, making a 20/2 that sits (46.5/2 = 23.3mm in front of the sensor)? Should work.

But isn't it a MF lens? A µ4/3 lens may need a very light AF group to focus quickly.

MayaTlab said:

That's the kind of prime that actually makes you fall in love with, and for
just $450.

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If Oly made a kit prime for $450 we'd hear lots of complains about the price.

Anyway, the Voigtländer design is probably patented?

The 17/2.8 seems fine. The only obvious optical "problem" I've seen in the DPR gallery pictures is some CA, but that's the type that can be corrected, hopefully automatically, with more raw converters in the future.

The MTFs are for wide open performance and wide open, the corners are not so important.

MayaTlab said:

I guess that considering the fact that the EP1 sensor is smaller than a 35mm sized one, doing the exact same lense as the Voigtlander one would cost a ridiculously low price, even taking account of the need for a very slightly more telecentric design due to the fact that there is a low-pass filter in front of the sensor (unlike the Leica M8).

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Hm... didn't you say the Voigtländer was for Nikon? Anyway, the M8 also has offset microlenses.

Making the lens more telecentric, moving the rear node forward, will if I understand correctly make the lens more tele, which has to be compensated for by adding a wide angle converter in the front.

In any case, it's not clear to me you can make a "small tweak" and expect size and optical performance to stay the same.

Just my two oere
Erik from Sweden

Ehrik said:

Ehrik said:

MayaTlab wrote:
The Voigtlander 40mm f2 for Nikon, for example.

Click to expand...

You suggest scaling everything to 50%, making a 20/2 that sits (46.5/2 = 23.3mm in front of the sensor)? Should work.

But isn't it a MF lens? A µ4/3 lens may need a very light AF group to focus quickly.

Ehrik said:

That's the kind of prime that actually makes you fall in love with, and for
just $450.

Click to expand...

If Oly made a kit prime for $450 we'd hear lots of complains about the price.

Anyway, the Voigtländer design is probably patented?

Click to expand...

just a quick word on the VL 12mm

this lens should show issues on our gear, its light path gets way out to 60 degrees off axis, so it would be prudent to seek some images on mFT before laying down the gold (if you know what i mean..)

Ehrik said:

The 17/2.8 seems fine. The only obvious optical "problem" I've seen in the DPR gallery pictures is some CA, but that's the type that can be corrected, hopefully automatically, with more raw converters in the future.

The MTFs are for wide open performance and wide open, the corners are not so important.

Ehrik said:

I guess that considering the fact that the EP1 sensor is smaller than a 35mm sized one, doing the exact same lense as the Voigtlander one would cost a ridiculously low price, even taking account of the need for a very slightly more telecentric design due to the fact that there is a low-pass filter in front of the sensor (unlike the Leica M8).

Click to expand...

Hm... didn't you say the Voigtländer was for Nikon? Anyway, the M8 also has offset microlenses.

Click to expand...

yes, and that helps considerably. the M8 has to cope with more off axis lenses, but holds with more limited FL lens designs being a RF. In this way they can optimise the offset of the microlenses for generally shorter FL lenses, with generally more off axis light. from the look of some wider M's on mFT, we are optimised the other way.

Ehrik said:

Making the lens more telecentric, moving the rear node forward, will if I understand correctly make the lens more tele, which has to be compensated for by adding a wide angle converter in the front.

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no, that would make it a wider FL Erik

what happens is the front and rear glass become larger and heavier for the same given aperture, the curves are the same but, they need to continue out more. The lens then carries a larger dia. filter. In effect, the lens becomes bigger and heavier for the same aperture.

4/3rds designs move that exit pupil further out in the order of 30mm.

Ehrik said:

In any case, it's not clear to me you can make a "small tweak" and expect size and optical performance to stay the same.

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indeed

Ehrik said:

Just my two oere
Erik from Sweden

Click to expand...

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MayaTlab said:

The Voigtlander 40mm f2 for Nikon, for example. Definitely more
expensive than the Olympus prime, but it covers full frame, is made
for digital, has excellent optical performances, outstanding build
quality. That's the kind of prime that actually makes you fall in
love with, and for just $450.

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This made for film and could be used for digital (probably it mean lenses have both surface coating). I am sure on film it would outstanding lens, but much less on digital camera (vignetting, resolution loss). Even Leica limited itself to x1.33 crop. There some fundamental problem - for high resolution lenses should be design near-telecentric and it is quite difficult with small mount/sensor ratio especially for wide-angle. Olympus and Leica are top optical companies and didn’t see anyone who could beat them in size+IQ+price. (Don’t forget Olympus test it lens for 20 line/mm and 60 line/mm.)

The voigt lense was just an example of the overall feeling I'd like to get with m4/3. And by the way, I'm currently using it on a D700, so I can assure you it simply rocks on digital. The only "complain" I have is indeed a fair bit of vignetting, but no more than the vignetting present on the Panasonic 14-42 m4/3 non-corrected (as shown on Photozone). Of course since it was made for (D)SLRs there is no way it could be implemented on a m4/3 body by just shrinking the size. My point was to show that it is very much possible to make fine optics at a low price, bright and even small as hell. Here, from all the samples I've seen of the 17mm f2,8, I find them lacking in lots of ways, especially in terms of "bite", or "microcontrast", while the zoom fairs better in this regard. Of course the price of the prime is just very good, but so is the price of the zoom, while it seems to be a more complex design. I'm basically saying that I find this prime absolutely boring. In contrast, the expected Panasonic, if priced accordingly (to me it means not too low to sacrifice performances, not too high to be relevant with the price of m4/3 bodies), is much more exciting : bright, small. So to sum up, I just wished Olympus would have been bolder and would have conceived an optic that would match the very good progresses they seem to have made in other image quality departments (noise, DR, and now resolution with a weaker AA filter) .

what the diameter of the objective is on the 17mm? Biggest falloff is at about 8-9mm from center. How much wider than 16mm is the lens? Is 100% of the edge area even used for imaging?

This is a pretty small lens, so just wondering.

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Mingjai said:

And here's what I've seen for the Panasonic 14-45:

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The only problem with a direct comparisons is that Oly labels 60 line-pairs/mm as their sharpness threshold, and Panasonic uses a much "kinder" 40lpm. Both rely on 20lpm for the contrast lines. I went and looked, and Sigma/Canon both use 10/30 (contrast/sharpness).

--
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Ehrik said:

Ross said:

They might acually use an optical bench, like many optical designers have done for years.

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Some manufacturer(s) - I don't recall which - use theoretical MTF,
i.e. ray tracing / point spread function simulations, which
hopefully gives a correct representation of a perfectly centred and
aligned lens [Edit: A lens money can't buy...]

Ehrik said:

System MTF or Lens MTF, that is the question.....

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Part of the system MTF would be the incidence-angle softness /
smearing seen with wideangle M lenses, but which is probably present
to a small degree with most lenses

Just my two oere
Erik from Sweden

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Hi Erik,

The best data base that I've seen was one there in Sweden that had access to Hasselblad's optical bench and rated the lenses 0 to 5.0, based on the average MTF for all apertures. During this senerior moment, I can't remember th name of the site...;-\

System MTFs will have everything between the target and the observer, AA, IR, blurs in the Bayer filter, the Bayer dance....traffic vibrations......LOL
--
Bob

Hokuto said:

what the diameter of the objective is on the 17mm? Biggest falloff is at about 8-9mm from center. How much wider than 16mm is the lens? Is 100% of the edge area even used for imaging?

This is a pretty small lens, so just wondering.

Click to expand...

the front optic scales to 12.88mm, using 37mm filter dia. as a guide
not totally reliable but there you go

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Thanks, Riley. I don't know enough about MTF to do more than hazard dumb guesses, but isn't drop-off at 8mm from center a much more serious issue on a lens with large elements than one with small elements like this one? I wonder if we're even talking about a visible part of the lens??? (like I said, it's just a dumb guess).

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Hokuto said:

Thanks, Riley. I don't know enough about MTF to do more than hazard
dumb guesses, but isn't drop-off at 8mm from center a much more
serious issue on a lens with large elements than one with small
elements like this one?

Click to expand...

You might be confusing MTF falloff for light falloff. AFAIK the only thing that can be generalized from the diameter of a WA lens (where "FL/apeture = minimum diameter" does not generally matter) is the propensity for vignetting.

Somebody with a background in optical design will have to comment.

--
-CW

よしよし、今日も生きのいい魂が手に入ったな

Hokuto said:

Thanks, Riley. I don't know enough about MTF to do more than hazard dumb guesses, but isn't drop-off at 8mm from center a much more serious issue on a lens with large elements than one with small elements like this one? I wonder if we're even talking about a visible part of the lens??? (like I said, it's just a dumb guess).

Click to expand...

ahh, i see what you are after now
no its actually about the image circle, and the plot goes from centre to corner

its not a great set of lines, but like i always advise, pancakes in these FL are optically compromised.

Even given that, its the sort of lens and performance that for example wouldnt trouble a street shooter, but i wouldnt want to be shooting interiors with it, the loss of contrast toward the corners would be a lot more noticeable (not that its wide enough anyway)

you can further baffle yourself here

http://www.luminous-landscape.com/tutorials/understanding-series/lens-contrast.shtml


really we still need a lens test to make more from the lines,
perhaps Andy or Richard will choose to respond on that proposition.

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Ross said:

The best data base that I've seen was one there in Sweden that had access to Hasselblad's optical bench and rated the lenses 0 to 5.0, based on the average MTF for all apertures. During this senerior moment, I can't remember th name of the site...;-\

Click to expand...

Bob, you must be thinking of photodo.com. Their name and database were bought a few years ago. The new owner is testing lenses too, but AFAICT they have no optical bench, but use something like Imatest and MTF50.

Just my two oere
Erik from Sweden

Mingjai said:

And here's what I've seen for the Panasonic 14-45:

Click to expand...

You have to be careful making a comparison. You can see that Panasonic show results for 20 and 40 line pairs per mm. Olympus show results for 20 and 60 line pairs per mm.

So the top lines are comparable but the lower lines are not. If Panasonic used 60 lp/mm, the lower lines would move down the chart. How far? Who knows!

Anton AK said:

JoeVC said:

I'm assuming the lenses were tested sans u4/3 camera body?

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I don’t think they need to copy primitive technique used by so called
“reviewers” at DPR.

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MTF charts are usually calculated from the lens design so are theoretical. However, they still give an indication of the relative performance of lenses and their strengths and weaknesses.

Imagine a circle that just cover the rectangle area of the 4/3 sensor. The light fall of will be at its largest in the area 8-9mm from the center of the circle. How wide the lens is, should not have anthing to do with the result of the falloff.

Hokuto said:

what the diameter of the objective is on the 17mm? Biggest falloff is
at about 8-9mm from center. How much wider than 16mm is the lens? Is
100% of the edge area even used for imaging?

This is a pretty small lens, so just wondering.

--
'And only the stump, or fishy part of him remained'

http://www2.gol.com/users/nhavens
A Contemplative Companion to Fujino Township

Click to expand...

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************
Torstein

MacroManUK said:

MTF charts are usually calculated from the lens design so are
theoretical. However, they still give an indication of the relative
performance of lenses and their strengths and weaknesses.

Click to expand...

Every company tested it’s product. Doesn’t matter what it produce: airplane, washing machine or lenses. MTF could be calculated theoretical, but it in any case needs to be tested to see if prediction/calculation was correct.

P.S. Good luck flying not certified aircraft!

Gidday Riley & All

The MTF charts seem to be using a distance from centre to edge that is not correctly the measurement of the 4/3rds sensor ... WTF?

How can the MTF measurement graph have values for distance from centre to edge greater than half the imaging width, which is 17.3mm (divided by two = 8.65mm)?

The graphed values extend well beyond this figure of 8.65mm, and that is where the "performance" of the lenses appears to be so very bad.

Can someone please explain this to me? I am somewhat confused by this.

--
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John King said:

Gidday Riley & All

The MTF charts seem to be using a distance from centre to edge that is not correctly the measurement of the 4/3rds sensor ... WTF?

How can the MTF measurement graph have values for distance from centre to edge greater than half the imaging width, which is 17.3mm (divided by two = 8.65mm)?

Click to expand...

MTF charts usually don't show the distance from the center to the edge, but the distance from the center to the corner.

BTW, I'm very happy to see that also the Australian posters here finally accepted the true 4/3 sensor size.

John King said:

Can someone please explain this to me? I am somewhat confused by this.

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That's what hanging here does to people. Save yourself before it is too late.

Cheers,

Jonas

Gidday Jonas, long time, no see, mate.

Jonas B said:

John King said:

Gidday Riley & All

The MTF charts seem to be using a distance from centre to edge that is not correctly the measurement of the 4/3rds sensor ... WTF?

How can the MTF measurement graph have values for distance from centre to edge greater than half the imaging width, which is 17.3mm (divided by two = 8.65mm)?

Click to expand...

MTF charts usually don't show the distance from the center to the edge, but the distance from the center to the corner.

Click to expand...

Thanks for that explanation, Jonas. 10.82 mm it is then.

The lens widget here is a far better tool for showing lens performance, IMNSHO. FULL marks to DPR for that bit of programming!

Jonas B said:

BTW, I'm very happy to see that also the Australian posters here finally accepted the true 4/3 sensor size.

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No one has ever disputed this, AFAIK. (BTW, the E-1 has a different imaging size ... ).

What has been disputed is that the actual imaging area is used for the 4/3rds sensor, BUT the nominal sensor size is used for everyone else's, as their actual imaging area is a "State secret", LOL! One must use either one or the other for both, and since we do not know the actual imaging area for almost all other sensors, it is only right to use the nominal imaging area for all sensors.

For 4/3rds, the nominal imaging area is 18.0 x 13.5 mm ... The nominal area is 8.1% larger than the actual imaging area, and this could reasonably be expected to be similar for all sensors ... So use one or the other, but not one for 4/3rds and a different one for everyone else ...

Since this difference is used by every flaming troll under the sun to bash Olympus and 4/3rds, Jonas, is it really any wonder that there have been so many fights about it?

Jonas B said:

Jonas B said:

Can someone please explain this to me? I am somewhat confused by this.

Click to expand...

That's what hanging here does to people. Save yourself before it is too late.

Click to expand...

You are quite right there, mate! Lol

Jonas B said:

Cheers,

Jonas

Click to expand...

And to you, Jonas

--
Regards, john from Melbourne, Australia.
-- -- --

The Camera doth not make the Man (or Woman) ...
Perhaps being kind to cats, dogs & children does ...

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Ditto! Without good lenses, we all might as well use a Sony point-and-shoot. Ability to use bright, sharp, and distortion-free primes is the main point of having an interchangeable-lens camera. C'mon Olympus, you should know how to do it.