Testing Reverse mounted Minolta 45mm Lens

August 19, 2018 - Photography
Testing Reverse mounted Minolta 45mm Lens

I tried out the reverse mounted 45mm Minolta lens to get a good idea of what it can do, and to compare it to other lenses that I will be testing next. I want to find out what characteristics this lens may have, because with the first few times I have used it, I got some unexpected results that were initially concerning. After testing it out, I think this lens has potential for some specialized photos, and performs reasonably well as a macro lens when using extension tubes.

I made up some cards to help test color and sharpness in different sizes, to suit different lenses. Some lenses will focus very closely, and others, with wider angle, will have larger images to shoot.

These targets were the ones I used for the three different configurations with this lens. The Large target was the lens pictured above, and the smaller ones filled the frame when I used the Extension Tubes shown here…

The first test I did was using all of the extension tubes, which are a total of 52mm additional distance the lens is from the camera sensor, which allows for very close focus.

The frame is only 29mm wide, which means the image that is projected onto the sensor is actually bigger than whatever I would be taking a picture of, and this is true “macro” photography, by definition.

Here is a test shot of marker caps for a color calibration test, showing the extreme closeup with this setup.

Part of the challenge of shooting macro photography is the incredible narrow depth of field. Most professional macro lenses start to lose some quality with sharpness when using a higher f stop, where it also has a deeper depth of field. This set up, I found that the low f stop only has 1mm of depth that is in focus, while when the aperture is closed all the way at the high f stop, I am seeing 3mm of really sharp focus.



The unexpected results I got with this setup is that it was a steady progression from a low f stop at f2.0 of poor sharpness, which increased to good sharpness at f16. It is also difficult to take photos with, as it requires a flash or very, very long exposures to get a good shot. I am using a pair of off camera flashes, but when shooting insects and spiders, it is hard to get the light into the scene, since this setup focuses at 2.8 inches in front of the lens!

The images are much sharper at the center of the frame than the edges, and sharpness improves with a high f stop.

Next, I took of half of the extension tubes off, which made the working distance about 3.6-3.9 inches away from the front of the lens. The depth of field ranged from 3mm-6mm, depending on the aperture (or f stop). At the lowest, f 2.0, it was pretty bad, and almost unusable, and at one stop higher, f 2.8, the sharpness increased greatly. Still, the sharpness is nothing great, and steadily increases up to f 16, as seen below.

These images are 53mm wide, and so it is a ratio of 1:1.5 for the life size vs the sensor size, and only 1:1 or greater (2:1, 3:1, etc.) are true Macro Photography. I am really interested in getting up close to my subjects, and can have other lenses that work much better at this distance, with better color, contrast and sharpness, so I quickly moved on to the next test.

Finally, I wanted to try the lens backwards without extension tubes. I have read that this has the potential to really zoom in a lot. However, in this case, I found that the focus range was 19 inches from the lens, and the depth of field for goo focus was 2-4 inches. Again, this lens in reverse got sharper with a higher f stop, and with the lowest f stop, I saw some huge image problems, which , may be useful for some creative and artistic endeavors. he Booker and blurring is very interesting, and there is much distortion and doubling of the images, light seeps to double and blur more than softer items. Play around with high contrast or illuminated items, back-light mist, or good for a fairy-tale image, or the toy scale effect?
It appears as if there is zoom motion around the edges of the frame, and the center has some sharpness, but irregular contrast from the surrounding areas. Only the very center is anywhere near sharp, perhaps the center 1/8th of the whole frame!

I will have to test this lens mounted in the normal orientation, where it is much sharper and has less distortion! Mounting this particular lens in reverse doesn’t seem to offer any benefit except for some extreme distortion. That being said, it is possible to get some decent shots, especially

with some post processing work. In the following images, I use RawTherapee to process the RAW images taken from the camera, I also used an off camera flash to get enough light to shoot hand held, some of these were taken outside, at night, with no ambient light.



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