Macro nuts

Started Jan 24, 2004 | Discussions thread
Ching-Kuang Shene
Ching-Kuang Shene Veteran Member • Posts: 6,359
Coolpix 4500 and Reverse Mounting

Reimar wrote:

Is anyone using their CP4500 with a reversed lens for super close-ups?
I just started experimenting with a reversed 50mm 1.7 Pentax.
Should I keep the focus set to 1.5 feet or infinity where the lens
is most compact?

You can set the 50mm to infinity and move from farther away toward the subject. The first focus lock is likely the one with highest magnification. Moving the lens and camera to its closest focus distance may not get you the highest magnification because the 50mm is REVERSED!

Do I have to worry about the flower icon being
yellow?

No, zoom the 4500 lens all the way in to its maximum focal length to get the highest magnification and minimize possible vignetting. Move the camera/lens to obtain an approximate focus and let the AF to finish the job. The 50mm can be left fully open if its center quality is good. Otherwise, close it down to its best, normally F4 or F5.6. However, if it makes focusing difficult, then use the widest aperture.

It seems I can focus even when the zoom is not in the
macro range.

See above. Take a look at these posts for more about reverse mouting:
http://www.stevesforums.com/phpBB2/viewtopic.php?t=15584
http://www.stevesforums.com/phpBB2/viewtopic.php?t=17817

Here are more examples using the 4500. The following is taken with the 4500 in macro mode. The magnification can be higher by zooming the lens in a little passing the yellow flower icon range. (Yes, the yellow flower icon DOES NOT provide you with the highest magnification.) The ruler image shows that at the largest magnification the 4500 macro mode records a height of 11.5mm length. The 4500 sensor has a dimension of 5.32mm x 7.18mm. Therefore, a length of 11.5mm is reproduced on the sensor as 5.32mm, and the magnification is 5.32/11.5=0.46X. More precisely, the 4500 can produce an about half life-size image of a subject.

The image below is taken with a reversed Minolta 50mm F1.4 on a 4500. Since the longest focal length of the 4500 is 32mm, the magnification is 32/50=0.64X, theoretically. From the image, since the recorded height is 9mm, the actual magnification is 5.32/9=0.59X, which is close to the theoretical result.

The reason that the 4500 cannot get very high magnification is due to its short focal length (i.e., 32mm). To increase focal length, you can use TC-E2 2X to make the combined focal length 64mm. The following image is taken with a 4500, TC-E2 and a reversed Minolta 50mm F1.4 on the TC-E2. The theoretical result is 64/50=1.28X. Since the recorded height is 4.5mm, the actual magnification is 5.32/4.5=1.18X, also close to the theoretical result.

To get an even higher magnification, what we need to do is to increase 4500 focal length again. The best solution is, of course, the use of TC-E3ED 3X. With the TC-E3ED, the 4500 combo has 32*3=96mm and the theoretical magnification of reversing a Minolta 50mm F1.4 is 96/50=1.92X. Now, look at the following image. The recorded height is 3mm, and, hence, the calculated magnification is 5.32/3=1.77X. That is, the recorded image is 1.77 times of the original Washington's right eye on a $1 bill.

To yield even higher magnification, you will need special lens. One of the most interesting lenses is Nikon Rayfact ED6 x 16D. See my 4500 user guide for the details. It is listed near the bottom of the home page.

A couple of points are important. FIRST, although 5.32mm x 7.18mm is used as the sensor size, the actual dimension for recording the image is slightly slower, and, as a result, the calculated magnification would be slightly higher and closer to the theoretical limit. SECOND, corner sharpness reduces with reverse mounting because large aperture and non-flat field lenses are normally not good for the reverse mount technique. THIRD, light fall-off is significant in the image taken by the TC-E3ED. This is because the TC-E3ED has a very large diameter, 72mm, and the Minolta 50mm F1.4 has a 49mm thread. The step-down rings plus a 49-49 macro coupler push the 50mm lens away from TC-E3ED, which contributes to the light fall-off. The main problem is that the TC-E3ED "sees" more than the 50mm can provide.

Hope the above helps.

CK
http://www.cs.mtu.edu/~shene/DigiCam
Nikon Coolpix 950/990/995/2500/4500/5700 User Guide

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