Sigma APO MACRO 180mm f/2.8EX, 1:1 resolving power

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LVF
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Sigma APO MACRO 180mm f/2.8EX, 1:1 resolving power

Post by LVF »

As requested by Lou Jost, I used the resolution chart (described in my post dated June 9th under user name LVF), to determine the resolving power of the Sigma APO MACRO 180mm f/2.8EX DG OS HSM lens at a 1:1 magnification. I photographed the chart at an effective aperture of f/5, and apertures f/5.6, F/8, f/11, f/16, and f/22. I did f/16 and f/22 out of curiosity as to how much diffraction sets in.

Note - I used my Nikon D500 camera with this lens. Nikon cameras records "effective aperture" when the lens is close-up at large aperture openings, f/2.8. In my case, when the lens is set at f/2.8, the camera reports an effective aperture of f/5 for a 1:1 photo. Canon and Sony cameras will report an aperture of 2.8 and not report the corrected aperture due to the affect of light loss within the lens at these close-up settings (although the exposure setting for these cameras will be correct for these close-up settings).

This is the computer generated resolution chart that was used for the 1:1 photographs:

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To clarify what part of the chart is showing in the following 1:1 photographs, I have identified sections of the chart as 2nd and 3rd circular bars:

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The portion of the resolution chart photographed at 1:1, is the most center part of the chart as shown here:

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Some dimensions are shown in this photo but are not shown on the actual print being photographed. The above photos are the computer generated photos, not the printed photo used to take photographs (the chart was printed on glossy photo paper with an Epson R3000 printer). The smallest bars and white spaces between these bars, (no. 6 on right side) have a thickness equal to the diameter of the average human hair, 0.004 inches or 0.1 mm, very narrow.

PLEASE NOTE
The following photographs are of the printed chart which is not as elegant as the computer generated chart shown above; the ink pattern is shown and the edges of the bars are jagged, not straight, and the colored inks used to make black are seen (magenta, cyan, and yellow). Also, the edges of the bars at 1:1 will not be tack sharp in the following CROPPED PHOTOGRAPHS because the ink spots are 0.0002 inches (0.005mm) in diameter. Any of these extremely small ink spots on the edges will appear blurry, even for this sharp lens. Also, the average width of the smallest "PRINTED BARS" is 0.004 inches or 0.1mm.

The camera was mounted on a tripod, and manually focused using live view. A Nikon MC-36 cable release was used to release the shutter. At 1:1, the front of the lens was 10 inches from the chart.

Here is the photo taken at an effective aperture of f/5 (f/2.8 for Canon and Sony cameras):

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The physical size of the photographed chart is approximately 0.9 inches by 0.6 inches (the size of the D500 camera sensor). To get a closer view, I cropped the 5624x3754px photo to 1024x1024 pixels:

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The printer used colored ink to make black, thus the colored ink spots in the jagged bars and numbers (cyan, yellow and magenta ink spots). As stated before, the average printed width of the smallest bars is 0.004 inches (0.1mm) , the diameter of the average human hair.

I am not going to show the photo taken at an aperture f/5.6 since it is essentially the same as the effective aperture f/5.

Here is the photo taken at f/8:

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Here is a 1024x1024px cropped photo taken at f/8:

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As expected, the bars are slightly sharper than those in the effective f/5 photo.

Here is the photo at f/11:

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Here is a 1024x1024px cropped photo taken at f/11:

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Upon really close examination, the f/8 photo is some what sharper than the f/11 photo, possibly diffraction starting at f/11?

Here is the photo at f/16:

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Here is a 1024x1024px cropped photo at f/16:

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There is the start of lens diffraction on the edges of the bars.

Here is the photo at f/22:

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Here is a 1024x1024px cropped photo at f/22:

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This photo show the affects of lens diffraction.

To really see the affects of diffraction, there are small, clear, round, white spots in some of the bars and numbers, which are clearly shown at f/8. As you look at these photos from f/8 thru f/22, watch these white spots, they show diffraction starting at f/11, the white spots start blurring, and by f/22, some disappear.

One may be under the impression that the photo at effective f/5 is as good as the photo at f/8. However, if you look closely for small circular white spots, more smaller white spots appear when you go from effective f/5 to f/8, f/8 is slightly sharper than effective f/5

In conclusion, it appears that if you want the sharpest images at 1:1 close-up, an aperture of f/8 should be used.

My next post will show photos taken with the Sigma 180mm lens at 1:2 close-up of the chart at a 14 inch working distance.

Leon

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Post by Daniel_Han »

:D Neat, exactly what I wanted to see!
Is it possible for you to also compare this to the Micro-nikkor 200/4 AFD? It's slower and also smaller. I'm still deciding between the Sigma and the Nikkor.
The world of Macro is a world that most people are missing.

LVF
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Daniel

Post by LVF »

Sorry, I do not have the Micro-nikkor 200/4 AFD.

Leon

Lou Jost
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Post by Lou Jost »

Hi Leon,
Thanks very much for this, and sorry it has taken me this long to see it. I was in the Amazon rain forest for two weeks. I've also just found your 300mm 1:2 tests and your Sigma 1:2 tests. I look forward to the comparison of the two, which you mentioned in that thread.

LVF
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Lou

Post by LVF »

Thank You Lou

I got side track. I have the Nikon 20E III teleconverter and, since it gives a 1:2 photograph with the 300mm lens, I am first going to post my results using this combination before making comparisons.

Leon

Lou Jost
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Post by Lou Jost »

I really like these Nikon teleconverters when used with sharp lenses. Many people are critical of them. Of course there are bad teleconverters, and good converters on bad lenses will also give awful results, but on a lens that out-resolves the sensor, a good teleconverter can work wonders.

RobertOToole
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Post by RobertOToole »

Hi Leon,

If it would help I own the Sigma 180/2.8, 150/2.8, 105/2.8, 70/2.8, 50/2.8, all macro 1:1 lenses.

I have tested them all in the center and 1:1 at the sharpest aperture, f5.6 and all the new generation, 180/150/105/70/50 are all very sharp without CAs in the center. It was a waste of time basically they were all so close.

I believe I posted it here on PM.net in the past but I can post it again if anyone is interested.

Robert

Lou Jost
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Post by Lou Jost »

Robert, maybe these differ in how good they are wide open? The 70mm in particular is surprisingly good wide open and in the corners.

RobertOToole
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Post by RobertOToole »

Lou Jost wrote:Robert, maybe these differ in how good they are wide open? The 70mm in particular is surprisingly good wide open and in the corners.
Hi Lou,

Correct you are. I tested them all where I shoot them @ f5.6-f/8. They were all awesome at the aperture. Almost identical.

I agree the 70 is special.

Where they do differ and why I keep them all is that they all have a certain look or character. The longer lenses have awesome bokeh and ease of background control. (I actually prefer the shorter lenses are easier to light and use in the field)

Lou Jost
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Post by Lou Jost »

Which is sharper wide open, the 150 or the 180?

I also like longer lenses for background control. I like the short lenses for reverse-mounting on longer lenses.

RobertOToole
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Post by RobertOToole »

Lou Jost wrote:Which is sharper wide open, the 150 or the 180?

I also like longer lenses for background control. I like the short lenses for reverse-mounting on longer lenses.
The 180 is sharper @ f/2.8 but, but, there is always a but, the 150 is almost, very close to and just about a super-apochormat, even less CAs than the legendary voigtlanders.

Lou Jost
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Post by Lou Jost »

Thanks Robert for that info. So the 180 has significantly more CA?

RobertOToole
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Post by RobertOToole »

Lou Jost wrote:Thanks Robert for that info. So the 180 has significantly more CA?
I haven't tested the lenses in awhile. I just shoot with them :-)

I do remember the 180 being optimized for wide apertures f/2.8-5.6. Stopping down to f/8-f/11 had slightly more CAs, going from almost nothing to slightly noticeable, about the same or maybe a little less than a Canon 180.
Its not what you would expect, less CAs stopped down?

The 150? You wont see any, period. Its amazing. No comparison when put head to head with a Zeiss or Canon 100.

Robert.

Lou Jost
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Post by Lou Jost »

Wow, how interesting! I'll have to get a 150. My current 150, a very expensive Oly f/2.0, does have mild purple fringing, though it is shockingly sharp, even wide open.

Published tests of this Oly 150 show that it is optimized to have minimal CA wide open and shows increasing CA the more it is stopped down, like your results with your 180 Sigma:
http://www.imaging-resource.com/lenses/ ... sub-frame/
http://www.imaging-resource.com/lenses/ ... sub-frame/

RobertOToole
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Post by RobertOToole »

Sorry for taking this off topic, this should be a new thread I think :-)

The 150f/2 sounds awesome but that must have been hard for the designers to optimize with all that speed!

I did find one CA test for the 150 OS sigma, from Lenstip.com.

These are lateral CAs.

Image

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