300MM F/4E PF + 17E II TC, 1:2 RESOLVING POWER AT 4 FT

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LVF
Posts: 66
Joined: Sun Apr 23, 2017 4:17 pm
Location: Sequim, Washington

300MM F/4E PF + 17E II TC, 1:2 RESOLVING POWER AT 4 FT

Post by LVF »

On July 1st, I posted the resolving power of the Sigma APO MACRO 180mm f/2.8 EX DG OS HSM lens at a 1:1 close-up working distance of 10 inches. And on July 7th, I posted the resolving power for this lens at a near 1:2 (measured 1:2.1) close-up working distance of 16 inches. By working distance, I mean the distance from in-front of the lens to the subject being photographed.

Today, I am presenting the resolving power of the Nikkor AF-S 300mm f/4E PF ED VR lens, with the Nikon 17E II Teleconverter attached between this lens and the Nikon D500 camera. This combination takes a photograph at a near 1:2 (measured 1:2.3) close-up working distance of 48 inches.

For me, since I can no longer kneel on the ground, a 1:2 photograph at 48 inches is a lot easier than at 16 inches. My hope is that this combination is near as good as the Sigma 180mm lens on my Nikon D500 camera.

I photographed my resolution chart (described in my June 9th post under LVF) at an effective aperture of f/6.7, and apertures 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 and teleconverter. Nikon cameras records "effective aperture" when the lens is close-up at large aperture openings (f/4). In my case, when the lens is set at f/4, the camera reports an effective aperture of f/6.7 for a 1:2 photograph. If this lens and teleconverter were attached to a Canon or Sony camera, these cameras would report an aperture of f/4, and not report the affect of light loss within the lens at these close-up settings (although, the exposure will be correct for the loss of light).


This is a photo of the computer generated resolution chart that was used for the 1:2 photographs:


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To clarify what part of the chart is showing in the following 1:2 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 1:2, is the 2nd circular bars as shown here:


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I will be showing crops of the 1:2 photos which will show the smallest 3rd circular bars:

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Some dimensions are shown in these two photos but are not shown on the actual print used to photograph the 1:2 photos. The above resolution chart photos are the computer generated photos, not the printed photo used to take the 1:2 photographs (the chart was printed on glossy photo paper with an Epson R3000 printer). The smallest bars and white spaces between these bars in the 3rd circular bars photo, (no. 6 on right side) have a thickness equal to the diameter of the average human hair, 0.004 inches or 0.1 mm.

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 1:2 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 and teleconverter combination. Also, to repeat, the average width of the smallest printed bars is 0.004 inches or 0.1mm.

The Nikon D500 camera was mounted on a tripod, and manually focused using live view. A Nikon MC-36 cable release was used to release the shutter. The shutter was released several seconds after I removed my fingers off the lens to reduce vibrations. At 1:2, the front of the lens was 48 inches from the chart.

I used DxO Optics Pro to open the D500 Nef files and exported these files as Dng files to Camera Raw CS6. Note - I did zero changes to the Nef files in DxO, no sharpening, no noise reduction, no exposure settings. I only used DxO to converter the Nef file to a Dng file.

In Camera Raw, I only adjusted the exposure, shadow, and black sliders. I did zero sharpening, and zero noise reduction. I transferred the psd file to Photoshop CS6. I did zero processing in Photoshop. I only used Photoshop to save the psd file by using "file>save to the web" to meet the file size requirements of this forum. What you see is what the camera recorded except for raising the exposure to brighten the photos.


Here is the photo taken at an effective aperture of f/6.7.

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The physical size of the photographed chart in this photo is approximately 2.1 inches by 1.4 inches (2.27 times the size of the D500 camera sensor).

To get a closer view, I cropped the 5568x3712px effective f/6.7 photo to 512x512 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.

Here is the photo taken at an aperture of f/8:

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I then cropped the f/8 photo to 512x512px:

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Here is the photo taken at f/11:

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I then cropped the f/11 photo to 512x512px:

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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? You can better visualize this by looking at the large black square in the two 512x512px photographs. There are very small white spots in the black square that are sharper in the f/8 photo; at f/11 some of these white spots are blurrier, and some of the very smallest white spots disappear in the f/11 photo.

Here is the photo at f/16:

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I then cropped the f/16 photo to 512x512px:

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There is definitely the start of lens diffraction. Compare the smallest bars at f/8 and f/16, the f/16 bars are blurred on the edges and some the smaller white spots in the black square are gone.

Here is the photo at f/22:

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I then cropped the f/22 photo to 512x512px:

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This photo show the affects of lens diffraction.

To see more clearly at what aperture diffraction starts, I croppped the 5-5568x3712 pixel photos to 256x256 pixels and combined the 5 cropped photos in one photo:

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Comparing these 5 photos clearly shows that diffraction starts at f/11. This photo also shows that this lens takes near sharp photos wide open at effective f/6.7, and at an apertures of f/8. Maybe effective f/6.7 is slightly sharper than f/8? You be the judge.

For these photos taken at 48 inches from in-front of the lens, and resolving bars 0.004 inches (0.1 mm) wide, I am very satisfied that this combination of photo equipment will take great 1:2 photographs at 48 inches.

My next post will compare the 1:2 resolving power of the Sigma APO MACRO 180mm f/2.8 EX lens at 16 inches, to the 1:2 resolving power of the Nikkor 300mm f/4E PF lens with the Nikon 17E II teleconverter at 48 inches, both mounted on the Nikon D500 camera.

Leon

genera
Posts: 127
Joined: Wed Oct 05, 2011 5:05 pm
Location: California, USA

Post by genera »

Leon,

There's a standardized way of calling out areas of the resolution target that make it unnecessary for you to define areas yourself and enable others, even without your instructions, to know the area you're referring to.

The convention is to break the markings into groups of 6 line pairs, aka elements, and number each element within the group. The group number goes up as you move clockwise around the target and each element has it's element number next to it. (On some targets, but not this one, the group is also numbered). In you first photo the largest pair is group1/element 1, labeled "1", in the lower right corner. Group 1/element 2 would be the top left pair. There's a black block between groups. Your smallest pair is group 6/element 6.

Some targets go as small as group 9/element 6 (they use a higher quality manufacturing process and can be quite expensive), and some go larger with groups 0, -1, -2, and beyond.

Look up "USAF 1951 resolution target" for more info.
-Gene

LVF
Posts: 66
Joined: Sun Apr 23, 2017 4:17 pm
Location: Sequim, Washington

Gene

Post by LVF »

I understand what you are saying. However, there are many amateur photographers who know nothing about something called "USAF 1951 Resolution Target".

I, myself, knew nothing about it until I wanted something to photograph to determine the resolving capability of my lenses. I had to go beyond just taking photographs and research this topic. I am sure most amateur photographs would not be interested in this topic.

Therefore, I will continue to explain the target for those who are not familiar with the target. Those who know all about the target should just ignore the intro.

Thanks for the explanation.

Leon

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