Prepared Resolution Chart for Close-up at 4 ft Work Dist.

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

Prepared Resolution Chart for Close-up at 4 ft Work Dist.

Post by LVF »

I have some great lens, teleconverters, and extension tubes, that produce 1:1 to 1:4 photos at 6 inches, 10 inches, 16 inches, and 48 inches. But do they resolve detail?

Except for Memorial weekend, the weather here in Sequim, Washington, has been wet, or cold, or windy, or all three at same time. Seattle, Washington, (approx. 60 miles east of Sequim), has recorded the wettest April thru May ever.

So I stay in my computer room doing mainly three fun things, 1) playing with Photoshop, 2) photographing my home made Nikon D500 camera close-up target (made with photoshop) using several combinations of lens, teleconverters, and extension tubes, and 3) photographing close-up of flowers at a 4 foot working distance. The results of these photos have been posted here in April and May under the user name "LVF".

So I ran out of things to do with my photography in my room. Then I had an idea; measure the resolving power (the ability to optically separate or distinguish small or closely adjacent images) of my lenses alone, or in combination with teleconverters and extension tubes. After all, I have shown in my posts that my photographic equipment is capable of producing 1:4 to near 1:1 close-up photos at a 4 foot working distance, and the photos looked fairly sharp.

I decided to use the USAF 1951 Resolution Test Chart to test my photographic gear. I have the chart but darn if I cannot find it. So I googled the chart and found several photos of the chart. However, the photos are very small and of low resolution.

I selected one of the low resolution photos, and resized it in Photoshop to 4 inches by 4 inches, the area covered by the Nikon D500 camera and the Nikkor 300mm f/4E PF lens at a 4 foot working distance. The resulting resized photo looked really bad:


Image

So I spent several hours re-doing the chart in Photoshop, starting with a smaller chart, and then re-sizing it to 4 x 4 inches, then reworking it again until I had a chart that was sharp. What I did in Photoshop was to turn every pixel with varying opacity values, into either 100% black or 100% white, (there were 1.5 million pixels) while keeping the length of black bars and width of white spaces between bars, as true to the USAF 1951 dimensions as possible. I then printed the chart on an Epson R3000 high resolution printer using glossy photo paper. Here is the final resulting 4 x 4 inch chart produced with Photoshop CS6:

Image

If you look closely, you will see that the chart consists of three circluar regions of bars, as pointed out in this photo (the outer bars forming the first region of circular bars):

Image

There is the outer circle of bars, then there is the second inner circle of bars which I have labled "2nd Circular Bars", and finally, the most inner circle of bars which I have labled "3rd Circular Bars".

Each circle consists of six sets of 3 horizontal bars and three vertical bars per set. Each of the three circles start with set #1 at the bottom right, then sets #2 thru #6 on the left side, then completes the circle on the right side with sets #1 thru #6.

Obviously, it is difficult to see the 3rd most inner circle of bars but I will be showing it enlarge later.

Using the printed chart, I took my Bausch and Lomb 7x magnifier (which has a scale in inches, with each division measuring 0.005 inches, and a scale in mm, with each division measuring 0.1 mm), and used it to measured the length of some bars and the width of the white space between bars.

Here are the measurements for the 2nd circular bars:


Image

And, as shown for the 3rd circular bars:


Image

For the next week or two, I will be using this 4x4 inch resolution chart to measure the resolving prower of the following combination of lens, teleconverters, extension tubes, and the Canon 500D close-up lens, all of which will be attached to the Nikon D500 Camera:

1) the Nikkor 300mm f/4E PF lens only, which gives a 1:4 photo at 48 inches working distance (distance from the front of the lens to the subject being photographed):


Image

And the following teleconverters attached between the D500 camera and 300mm f/4E PF lens:

2) the Nikon 14E III, which gives a little better than a 1:3 photo at 48 inches:


Image

3) the Nikon 17E II, which gives a 1:2 photo at 48 inches:

Image

4) the Nikon 20E III, which gives a 1:2 photo at 48 inches:

Image

5) the Kenko 68mm extension tubes, attached between the D500 camera and 300mm lens, which gives a little better than a 1:3 photo at 48 inches:

Image

Then I will use the following lenses at closer close-up working distances:

1) the Nikon Micro Nikkor 105mm f/2.8G lens, which gives a 1:1 photo at 6 inches:

Image

2) the Sigma APO MACRO 180mm f/2.8EX lens, which gives a 1:1 photo at 10 inches:

Image

And finally,

3) the Canon 500D close-up lens screwed on front of the Nikkor 300mm f/4E PF lens, which gives a near 1:1 photo at 16 inches.

Image

However, maybe I will not use the Canon 500D close-up lens because, as you can see, this combination is not as sharp as the other lens.

Now that I have a usable printed resolution chart, I will setup the chart and photographic gear in my computer room to take photographs, and see how well the combination of photograhic gear resolves detail.
Leon

Lou Jost
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Post by Lou Jost »

I look forward to seeing the results, especially of the Sigma 180mm. I hope you can try wide open and one stop down and two stops down. More than that is going to be unnecessary because diffraction will degrade the image.

enricosavazzi
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Re: Prepared Resolution Chart for Close-up at 4 ft Work Dist

Post by enricosavazzi »

LVF wrote:(...)
I decided to use the USAF 1951 Resolution Test Chart to test my photographic gear. I have the chart but darn if I cannot find it. So I googled the chart and found several photos of the chart. However, the photos are very small and of low resolution.
(...)
The Wikipedia article for this resolution chart links to a PDF version:
http://www.takinami.com/yoshihiko/photo ... t/USAF.pdf

I don't know whether this PDF chart follows all specifications of this target type (which are also linked to by the Wikipedia article), but it may save time if one wants to carry out comparable tests.
--ES

ChrisR
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Post by ChrisR »

Good tests! That's interesting, I found a Canon 70-300L at 300mm was much sharper using a (Nikon) doublet close-up lens than extension tubes.
Chris R

Lou Jost
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Post by Lou Jost »

Chris, that's been my experience too with long lenses.

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