This article was posted on Preview.com on June 7, 2014, nearly 10 years ago. I believe this article is an interesting one and may be useful to people here.
==================
Can we have a super telephoto lens without using a lens? Of course, we cannot. Therefore, there has to be a lens in front of the camera but it is not an expensive camera lens.
We will use a close-up lens but we don't do close-up shots. Here is what you need.
- You will need a close-up lens. Use an achromat (i.e., 2 elements in 1 group). This post uses a Canon 77mm 500D.
- Several extension tubes.
- A bellows. This post uses a Nikon PB-6; but, you could use whatever bland as long as you are able to convert the bayonet mount to a thread.
- Nikon has a K-2 ring that can just convert the Nikon F-mount to a female 52mm thread.
- A camera, of course, that can fit your bellows and your extension tubes. I chose a Sony NEX5 because this camera can be adapted to virtually all brands and because its peaking and magnification MF aids are very good. In order to mount this Sony NEX5 to the Nikon F-mount, I used a Nikon F to Sony NEX adapter.
- Some step rings.
- That is it!
The following image shows the tubes and adapter.
The following is the Nikon K-2 ring. It converts a female 52mm thread to the Nikon F-mount.
Since we have a 52mm female thread, various step-up rings are needed to increase the thread size to a female 77mm thread (left below). Then, put the K-2 to the end and we have our 500mm lens head (right below).
Put all stuff on the PB-6 and we have the following. Note that to balance the weight of the bellows system being used, extension tubes are used at both ends of the PB-6 bellows.
Put my Sony NEX5 at the end and we are ready to go:
How do I know this is a 500mm telephoto? Good question.
Although not every lens maker tells the power of a close-up lens, most makers show this information using diopter. The diopter of a close-up lens is defined as follows:
diopter D = 1000/focal-length
Thus, if you have a +2 diopter close-up lens, it has a focal length of 1000/2 = 500mm. If you don't know the diopter, you could do some tests to find it out and we won't discuss here. The Canon 500D has a focal length of 500mm (hence 500D).
What is the maximum aperture of this setup? Another good question.
It is about f/10. Hey, you may want to say that since the diameter of the Canon 500D is 77mm, the maximum aperture should be approximately 500mm/77mm = f/6.5. No, the Nikon compatible tubes all have a thread size of 52mm (see the above setup), and these tube act as the diaphragm of the lens (i.e., only the 52mm of the 77mm of the lens is used). This means the maximum aperture is 500/52 = f/9.6. Can we take the advantage of the full size aperture of 77mm? Yes, we can, but we will need a very long tube of 77mm in front of the bellows. This is currently impossible to do for me.
What is the minimum length of the setup?
Since the lens has a focal length of 500mm, the minimum length of the whole setup is at least 500mm for the lens to focus at infinity. When focusing to a closer distance, use the bellows to focus and the the whole setup extends. Therefore, to focus to a very close distance you will need a very long setup. For example, if you wish to do a 1:1 close-up shot, the image distance (i.e., the distance from the lens to the image sensor) is twice of the focal length. In our case, this setup must be able to extend to 500*2 = 1000mm! Those who played or are playing large format cameras know what I mean.
Now let us take a look at the image quality of this setup.
The distance from this bridge to the camera position is nearly 1km. The second image shows a 100% crop of the center area used for focusing.
This is a scene a bit closer, perhaps around 600m. The second image shows the focusing area and the two tags of the left most two vehicle.
This scene is about 50+ meters from the shooting position. The second and third image below show the center focusing area and the chains near the top edge.
Now let us get closer, about 40+ m. Not so bad. Isn't it?
This is a 30+m scene.
This is a 20+ m scene. Please look at how this Canon 500D resolves the details.
The following image was shot at a distance about 10m.
It does not make much sense if this setup is not used to shoot birds. Well, BIF is a mission impossible with thisheavy setup and its slow focusing mechanism. But, I managed to get one bird shot as shown below.
EPILOGUE
This is not a new idea. The first camera in 1839 used essentially the same setup. Before WWI and right after it lens makers used this idea to design long focal length lenses. The following are some 2E/1G long focal length lenses. Just a final note. Do not use single element close-up lens. Otherwise, you will feel sorry for your decision. More details will be posted elsewhere and will be updated in the future.
Enjoy!
Carl Zeiss Jena Fernobjektiv 500mm f/8
Asahi/Pentax Takumar 500mm f/5
Novoflex Novlexar 400 f5.6
Added Today (April 10, 2023, the day DPreview.com says Goodbye to us
No one can avoid shooting the moon with a 500mm lens. Here is my attempt. The second image was a 1200x1200 crop and then resized to 600x600. Exposure was corrected slightly followed by a weak sharpening to reduce a touch of thin cloud covering a portion of the moon.
A full version of this article (in Chinese) was published on June 15, 2014 and its translation by Google is available here. You will find more technical information and examples near the end of this article.
Hope you like this post.
Starting with tomorrow the world of photography will miss a great site and hope DPrevived will improve as soon as possible.
CK
