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Testing/comparing legacy lenses - how?
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PostPosted: Wed Jun 20, 2018 8:15 am    Post subject: Reply with quote
I generally test @f8 and check sharpness at 100%. First center then borders.

I don't output more than A3 size, so there is plenty room for my use and my eyes.

There are so many lenses... The feel in your hand, the quality of the built are other criteria I consider when I have to pick one lens in my collection before going out shooting. I don't always take the sharpest, because some less Shap lenses have strong character, and I like them for that.


PostPosted: Wed Jun 20, 2018 8:38 am    Post subject: Reply with quote
Lloydy wrote:
A lens test chart tells me nothing I want to know about a lens.


So, charts are not for you.

For my macro, I found I was unable to match the sharpness of images of other macro specialists. By comparing the macro lenses I owned, and by acquiring different ones and further comparing, I was able to chose my optimum lenses and now produce the images I could not obtain previously.

I am less concerned outside of the macro range and use a wide collection of lenses without bothering with charts.


PostPosted: Wed Jun 20, 2018 7:35 pm    Post subject: Reply with quote
norman j shearer wrote:

Another question. If a 42MB sensor (as in A7R2) outresolves a lens does that make the lens underperform or does that just mean you are not getting the max from the sensor?


The answer is: It depends!

The answer is not a digital Yes or No. Even a pedestrian Helios 44M at full aperture can show so exceedingly small details in the center of the image, that only a 500+ Mpixels would reveal. Nevertheless, the contrast of these details is extremely low.


norman j shearer wrote:
Just curious to find out how you guys test your lenses to see how they perform.


I think that to really knows a lens, one must scientifically test it.

What about completely testing a lens with only 5 or 6 shots? A mirror lens needs just ONE shot! In a few minutes you can assess the resolutions and get a pretty good idea of the lens aberrations (coma, astigmatism, CA), vignetting, decentering, mount/adapter tilt, etc. What more do you want?

What you need to characterize a lens is to measure the MTF50 across the field and for all apertures. The MTF50 is a particularly good measure of the resolution of a lens. Besides an appropriate software, you need a chart and a tripod. The chart must be at least 1 meter wide, but it can easily be constructed by juxtaposing A4 sheets printed with an ordinary printer.

I have used the MTF Mapper, a very easy to use and freely distributed software. I tested all my lenses and with it so now I know exactly how they perform. It is important to normalize the test conditions. For example, I shot RAW and convert to JPEG with ZERO sharpening, but correct the contrast and vignetting.

After you test your lenses with MTF Mapper, you must hnow how to interpret the measurements. For example, depending of the values of MTF50 in terms of line-pairs per mm (lp/m) you could classify the resolution as:

10 lp/m: POOR
20 lp/m: FAIR
30 lp/m: GOOD
40 lp/m: VERY GOOD
>40 lpm: EXCELLENT

To show how the MTF Mapper works, I present bellow the MTF50 of my Helios 44M for apertures from wide open to F8. I added some interpretations of the measurements.


F2 (wide open):

Reasonably well centered lens. Good resolution in the central are (10 to 15 mm diameter). Better for saggital lines. Poor borders, which would be noticed even for APS-C format.



F2.8:

The resolution in the center improved considerably. Borders still poor.




F4:

Borders much better now. Center resolution very good to excellent. Some decentering, but different according to the direction of measurement.




F5.6:

Resolution excellent in the central area and most part of the field. Good resolution at borders. Some decentering.




F8:

Even better than F5.6. Resolution can be considered excellent overall the field. F8 is the best aperture for this lens.


F11 and smaller apertures (not shown)
Resolution drops because of diffraction


PostPosted: Wed Jun 20, 2018 7:49 pm    Post subject: Reply with quote
What chart do you use with MTFMapper?


PostPosted: Wed Jun 20, 2018 8:01 pm    Post subject: Reply with quote
edri wrote:
What chart do you use with MTFMapper?


This chart:


PostPosted: Wed Jun 20, 2018 10:08 pm    Post subject: Reply with quote
e6filmuser wrote:
Lloydy wrote:
A lens test chart tells me nothing I want to know about a lens.


So, charts are not for you.

For my macro, I found I was unable to match the sharpness of images of other macro specialists. By comparing the macro lenses I owned, and by acquiring different ones and further comparing, I was able to chose my optimum lenses and now produce the images I could not obtain previously.

I am less concerned outside of the macro range and use a wide collection of lenses without bothering with charts.


I'd never disagree with that statement, for the precision of macro work sharpness is king, and chart testing is essential. And again I certainly wouldn't disagree with not using charts for lenses that we use for 'general photography' where the complete character of the lens, which must include sharpness to the degree we find acceptable, is something charts alone just cant tell us.


PostPosted: Wed Jun 20, 2018 11:38 pm    Post subject: Reply with quote
Gerald wrote:
...
I have used the MTF Mapper, a very easy to use and freely distributed software. I tested all my lenses and with it so now I know exactly how they perform. It is important to normalize the test conditions. For example, I shot RAW and convert to JPEG with ZERO sharpening, but correct the contrast and vignetting.

After you test your lenses with MTF Mapper, you must hnow how to interpret the measurements. For example, depending of the values of MTF50 in terms of line-pairs per mm (lp/m) you could classify the resolution as:

10 lp/m: POOR
20 lp/m: FAIR
30 lp/m: GOOD
40 lp/m: VERY GOOD
>40 lpm: EXCELLENT

To show how the MTF Mapper works, I present bellow the MTF50 of my Helios 44M for apertures from wide open to F8. I added some interpretations of the measurements.
...



+1!

Measures how your lens performs on your camera!


PostPosted: Mon Jun 25, 2018 8:08 pm    Post subject: Reply with quote
Gerald wrote:
edri wrote:
What chart do you use with MTFMapper?


This chart:


Thanks, where is possible to find this chart at higher resolution?


PostPosted: Mon Jun 25, 2018 10:21 pm    Post subject: Reply with quote
Thank you Gerald for the Input.

From what I understand you use the "old" chart because I can not found it.


"...This new revision can still use the original resolution and focus chart designs, which is a real relief if you have invested time, effort, and money in printing/mounting large versions of the charts. If you print the newer charts, you get some new and welcome abilities...."

https://sourceforge.net/projects/mtfmapper/?source=typ_redirect

https://www.photoartfromscience.com/single-post/2016/10/12/MTF-Mapper-Version-058


I don't need that much precision, but when weather is bad, I think it is a good idea to have this chart for testing on some occasion. Anyway you convince me ! Like 1 small

Thanks again for the explanation, I am going to look further.


PostPosted: Mon Jun 25, 2018 10:58 pm    Post subject: Reply with quote
edri and willy35,

My (old) version of MTF Mapper came with a test chart generator for A0, A1, A2 and A3 sizes. I suppose the current version comes with a chart generator, too. I can send you the PDF files of the old charts if you want.
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