The purpose of any objective is to guide the light into the camera and project a focused image in the camera sensor. Any convergent lens can do that, does not need to be a very complex system. All objectives available are complex in order to obtain the best image possible.
In a simple way, if we put a lens between a subject and the camera we can get a focused picture, only depends on the distances between the elements.
If we have the subject far away of the lens, we get an inverted and smaller image than the subject in the other side of the lens.
Projecting an image of an object through the lens (click to enlarge)
If the thickness of the lens is negligible, we can apply the thin lens formula: 1/S1 + 1/S2 = 1/f
- S1 is the distance between the object and the lens
- S2 is the distance between the image and the lens
- f is the lens focal length
For a positive / convergent lens, putting an object at S1 and S1 >> f, we will have a sharp image in the other side of the lens at S2, we can see that by putting a screen in S2 and changing the distance from the screen to the lens the image gets sharper or blurred.
For distant subjects (when S1 tends to infinity), the distance between the lens and the image (S2) is slightly greater then lens focal length (is approximately the same).
I'll show how to set an objective and take shots with a magnifying glass.
In order to protect the camera and achieve a better result, I used extension tubes to position the lens properly and reduce dust and light leakage to the sensor. Using some sort of diaphragm also improve the image quality and without it the image tends to be more blurred. The diaphragm can be something dark with a small hole in the middle.
Note: You should avoid dusty environments to protect the sensor of the camera.
Mounting the lens / Lens and diaphragm / Extension tube
This lens has a focal distance of around 120mm, with the extension tubes it's possible to adjust the distance between the camera sensor and the lens.
Test shot of this lens vs 100mm regular objective
Test shots
DisclaimerI am not associated to any kind of brand.
I claim no responsibility if you damage your gear, electrocute yourself, inflict or receive any harm or misfortune.
By undertaking this guide you do so at your own risk.
Whilst I have made every best effort to insure that these instructions are accurate, given the fact I am not a professional there may be errors. If you find any please let me know.
Let's get onto the building :)
Have fun
