Resolution power of Medium format lenses

[kevin h. y. lui.]

I am curious to know whether the resolution power of the medium format lens is

higher or lower than 135 format. I read some old Chinese magazines and they

claim that the resolution power is much less than 135 format (or much smaller

format). The magazine claims that because the differences of format size, lenses

of medium format allow to use a lower resolution power one.

Is it true that medium format lenses are having lower resolution power than

smaller format? I have never heard this in other magazines.

[mike_earussi1]

Varies dramatically with the lens. The old Russian lenses can be as low as 30 LPM. Hassiblads have around 60-70 LPM. Rolleis come in at around 80 LPM. But the best ever made are the ones for the Mamiya 7 at over 100 LPM, which are as good, if not better, than most 35mm lenses. That's why, even though all other MF cameras have dropped dramatically in price, Rolleis and Mamiya 7s still command top dollar.

[derek_stanton2]

In general, yes, MF lenses have lower resolution than lenses for the 24x36mm format, and

it's the MF film size (less enlargement required) that compensates/overcomes the difference.

I've not seen this in a magazine, but it's pretty commonly discussed online.

[q.g._de_bakker]

This idea is a remnant from the days when people first tried to convince photographers that subminiature 35 mm format was good for anything (some 80 years ago, yes).<br>The story was that to be indeed good for anything, and compete with large® formats, the lenses used on 35 mm format cameras just had to be better than the ones used on these larger format cameras (at the time, medium format was also considered a small, amateur format), to be able to equal their results.<br><br>This "have to be" somehow got twisted into "are", and that idea is what stuck with us ever since.<br><br>The truth is, some 35 mm format lenses are better, some are not. Some medium format lenses have higher resolving power than 35 mm lenses, and some do not.<br><br>What remained very true, however, is that 35 mm lenses <b>have to be</b> better for the small format to be able to <b>equal</b> larger formats.<br>Given that - though some are - they generally are not, the format advantage still stands, and you get better results using medium format (and better still using large format).

[q.g._de_bakker]

I don't know where those figures come from, Mike, but they seem rather low. For instance (and though this is an exceptionally good lens, as far as resolving power is concerned) the Zeiss 40 mm Distagon resolves up to 200 lp/mm. If you can find film that's able to capture that. ;-)<br>'Lesser' MF lenses have no problem breeching the 100 lp/mm barrier either.

[sal_santamaura]

<A HREF="http://"www.hevanet.com/cperez/MF_testing.html">www.hevanet.com/cperez/MF_testing.html</A>

[michael_darnton1]

This has become an interesting question to me lately, because with "35mm"-type DSLRs quickly approaching the resolution of some lower-end MF digital backs (the ones I might actually be able to afford), I've been wondering if the 35mm-DSLR version of 24MP might actually give better results than the MF version, due to any inferiority of MF lenses. It seems, then, that this might be a question that really depends on the specific lenses being discussed?

[mike_earussi1]

Q.G. de Bakker, you are correct if I were talking about free air resolutions, but I'm not, these figures are from actual tests I've read using film. Specifically, the one for the Rollei came from a 1968 Modern Photography test using Pan X. That same year they also tested the Hassiblad 80mm, which came in around 60 LPM and the 80 from the Mamiya 330 which was around 45.

[stwrtertbsratbs5]

Lots of tests here:

 

http://photodo.com/

 

There are other reasons to use format larger than 35mm. Tonality is better with lesser enlargement. And movements are practical with large format.

[mike_earussi1]

And here:

 

http://www.hevanet.com/cperez/MF_testing.html

[dan_fromm2]

Mike, the Russian lp/mm measures are taken with the lens wide open, aren't comparable with much published in the west.

 

If you want a heap of 'em, go here: http://www.lallement.com/pictures/files.htm and download the 1963 GOI catalog and the two Yakovlev catalogs. You don't have to read Russian but it helps.

 

QG, getting 100 lp/mm on film in normal photography is excruciatingly difficult. I'm astonished that Perez and Thalmann did it with a few lenses. In photomacrography, separating details 10 microns apart cleanly isn't that hard at reasonable magnifications, but is a different problem.

 

Cheers,

 

Dan

[danny_wong2]

It is all a myth.

 

I have used the Pentax 67 400/4 and 645 300EDIF/4 on my LX on K25 on the same roll under controlled enviroment of my studio. You could not tell the difference between them and the FA*300/4.5 under projection by a Leica projector.

[dan_fromm2]

Danny, you're no fun and yours is not the only evil mind around.

 

To preserve solidarity among Dans, I must confess that I shoot a number of process lenses on my Nikons and that some of them are better than the comparable Nikkor prime. In particular, 210/9 Konica Hexanon GRII beats my 200/4 MicroNikkor AIS in a big way at 1:2 and at 30' from f/9 down. At f/4, there's no contest ...

[kevin h. y. lui.]

I see. But is it still true that 135mm lenses has a better resolution power than MF lenses in nowadays?

[danny_wong2]

Dan:

 

How about the 120Macro Nikkor, the 4X5 one on a bellow at 120, 135 or APS-c.

Maybe I should borrow a Nikkor 500T and try it on smaller sensors.

This should be fun.

 

Kevin:

 

You can't generalize, there are MF dog lenses and 135 dog lenses. I have not bought a 300 lens for my 35/apsc for my 300 from MF is that good.

[q.g._de_bakker]

Kevin,<br><br>The answer running all through this thread is: no, it never was true that 35 mm format lenses have better resolving power than MF lenses.<br>Some may do, others do not.<br><br>The only thing that was, and still is, true is that they will <b>have to</b> be better for 35 mm format to be able to come close to or equal MF quality. And that the fact that they "have to" does not mean they indeed "are".<br><br>You can say the same, but the other way around - just like the magazine did: MF lenses <b>do not need to</b> have a resolving power as high as that of 35 mm format lenses to produce results just as good as 35 mm format with better lenses can produce. And here again "do not need to" does not mean they "are not".<br>Some are, some are not.<br><br>There is a 'general rule' though, that has proven to be true: you cannot equal the results MF produces using 35 mm format. You never could, and you never will.

[dan_fromm2]

Kevin, QG has the right of it.

 

Just think of the arithmetic. Nominal 6x9 is a little more than twice as big as 24x36 on both dimensions. To get as good a print from a 24x36 negative as from a 6x9 one, the 24x36 neg's on-film resolution has to be twice that of the 6x9 one. This is really hard to accomplish.

 

I've never understood why some people who shoot 35 mm spend fortunes on slightly sharper lenses when they can get much better image quality in the final print, and at much lower cost, by moving up in format. QG and I don't agree on exactly where the limit is, but there is a limit to how much a negative can be enlarged. Once you hit it, the only way to get an acceptable larger print is to move up in format.

 

Cheers,

 

Dan

[kevin h. y. lui.]

Oh...Thank you very much for the correction.

[mohir_ali]

It is said that the lenses for the Minox subbies are quite good because they have to be.

[Ed_Ingold]

The comparison of 35mm and medium format lenses inevitably results in a philosophical debate rather than one supported with numbers. My practical experience is that both 35mm and medium format resolution is limited by the medium (film or digital) and not the lens. Most film has a practical resolution of 50-60 lp/mm (real-world contrast not 1000:1 metallized targets), so it doesn't take much of a lens to exceed the basic needs by a substantial margin*.

 

I agree completely with Q.G.'s argument that "what is needed" is not the same as "what is". There is a paucity of objective data regarding the resolution of either 35mm or medium format lenses. The published MTF curves represent a survey of contrast from center to corner at various frequencies rather than contrast vs. frequency, from which resolution can be extrapolated at zero contrast. You can infer a little about resolution from the usual plots, but not much.

 

Secondly, much of the resolution data is flawed or the experimental method is unclear. Hasselblad claims that their measurements are made using film, many measurements are made using the aerial image (microscope and photometer, no film) and some (notably Canon) plot calculations based on the design solution and ray-tracing software, which ignores manufacturing tolerances. Consequently, you have little basis for comparison.

 

*The performance of any system is based on the sum of its components. Resolution (uncertainty) can be estimated from the root-sum-square of these components (film/sensor and lens) and is ALWAYS less than either. This leads to an interesting phenomena - if the lens is significantly sharper than the medium (e.g., by a factor of two), then a sharper lens yet (e.g., x4) has relatively little effect on the results. Since Hasselblad claims one lens (CFE40/4 IF) has a resolution of 200 lp/mm using camera and film, one suspects the data is either fudged or another method was used.

[q.g._de_bakker]

Edward,<br><br><i>"[...] from which resolution can be extrapolated at zero contrast"</i><br><br>That's easy even without curves of any kind: at zero contrast resolution is the same, zero.<br>;-)

[q.g._de_bakker]

P.S.<br><br><i>"Since Hasselblad claims one lens (CFE40/4 IF) has a resolution of 200 lp/mm using camera and film, one suspects the data is either fudged or another method was used.

"</i><br><br>It was Zeiss, not Hasselblad who published the data, and the method they used (take pictures on film, and examine the negative using a microscope) was described in the link i pointed you to in another thread.<br>;-)<br><br>To continue the "theoretical considerations do not describe reality"-theme of this thread: the fact that the system resolution is less than that of the component parts does not mean a lens and film cannot produce images in which detail is recorded as fine as 200 lp/mm.

[Ed_Ingold]

The value of MTF represents contrast on a scale of 0 to 1 - the ratio between the brightest and dimmest image of the test pattern. When you plot MTF vs frequency, the curve slopes downward as frequency increases. The ultimate resolution is the frequency of that line extrapolated to zero MTF. The same test is used to estimate the resolution of film, and most manufacturers publish MTF charts to this effect.

 

It would take an extraordinarily sharp film to record an image at 200 lp/mm - probably for a technical application. You might squeeze this out of Kodak Technical Pan under laboratory conditions. In order to do so, the lens would have to resolve much more, perhaps 800 lp/mm, which borders on the implausible for a photographic lens. The Zeiss white paper (I stand corrected on the source) indicates no extraordinary methods were used, rather standard film, in a standard camera, of a subject with normal contrast ratio. This might sit well with the choir of believers, but I remain skeptical.

[Ed_Ingold]

A microscope would be used in any analysis of resolution. As the divisions become very small they become blurred, approximately sinusoidal variations in density. It is highly subjective to interpret these patterns by eye, hence the objective method of measuring and plotting the contrast ratios of these variations. The resolution is the frequency as this data is extrapolated to zero contrast, which you can't see anyway regardless of the magnification.

 

You could, of course, accept subjective results as a matter of faith. Faith-based photography is not the exclusive domain of Leica owners ;-)

[q.g._de_bakker]

Edward,<br><br>That's right, contrast, and with it MTF, will go towards zero when a lens is presented with detail it can no longer resolve. Resolving power will than be, uhm... , zero too. ;-)<br>The concept of resolving power at zero contrast is an empty one. It only contains faith... ;-)<br>But yes, there is a frequency limit, at and beyond which a lens will not be able to record anything.<br><br>MTF, by the way, is not the ratio between the brightest and dimmest part of the image.<br>It is (somewhat simplified) the ratio of the contrast in the target, to the contrast in the image a lens produces of that target.<br>(Or the ratio of the ratio between the brightest and dimmest part of the test pattern to the ratio of the ratio between the brightest and dimmest part of the image of those brightest and dimmest parts of the test pattern. ;-))<br>You can express that ratio in a two way, the most usual being as an percentage.<br><br>We have discussed those "extraordinary sharp films" <a href="http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=00Oqtn" target="_blank>before</a>, haven't we?<br>Though the best, better-than-200-lp/mm films have been discontinued, run-of-the-mill films like T-Max, used in an everyday (but careful) way, still come pretty close: <a href="http://www.zeiss.com/C12567A8003B58B9/Contents-Frame/48D8F331DF48EE72C1256CEF002B0240" target="_blank">"Resolving power of photographic films", Camera Lens News 19, March 2003.</a>