DIY Add on diopter

Started 10 months ago | Discussions
dickiedoo
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DIY Add on diopter
10 months ago

I had a friend give me an old lens,,,a Kiron...... f3.8 - 5.6......28-210mm. The outer shell/tube/barrel whatever you call it was pretty badly beaten up and I didn't have any use for it.My curiosity got to boiling and I disassembled it,,,,didn't find anything I might use inside but the main lens assembly,a metal tube about an 1 1/4" long and 3/4" diameter with glass in both ends.It looks like a front lens off of a microscope. This thing by itself is a very powerful magnifier,I could fashion a mount from an old lens cap and filter ring and make a add on diopter,don't have a clue if it could find a focus point or be clear etc etc etc but I think I'll give it a try. I'm sure it will have a vignette problem but might be okay for little guys smaller than fleas if it will focus.

I did an assembly of the above a little while ago and it will focus,vignette was not a problem but the image is cloudy and if that can't be fixed then it's history and a new toy for the grandkids. I'm not sure how it compares to a R 250 with out getting a fix on the cloudiness so sharp focus could be seen and tweaked. It's crystal clear by itself but when coupled with the glass in the SX50 it becomes cloudy.

dickiedoo

Stephen Barrett
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Re: DIY Add on diopter
In reply to dickiedoo, 10 months ago

Hello dickiedoo,
I think that your diy closeup lens ought to work. It may be so powerful that the depth-of-field is very tiny, so you may have to take some pains to focus it.
The Raynox 250 is 8 diopters or (1000 / 8) = 125 mm focal length.
You can get an approximate measure of the focal length of your closeup lens by focusing a distant scene (eg a tree outside the window) onto a wall and measuring the midpoint of the lens to the wall.

Here are a couple of home-made closeup lenses that I made from scrap parts:

http://forums.dpreview.com/forums/post/50119908

For hand-held shots, I find that the 600 mm lens is easier to use than the Raynox 250 and I use it fairly often.  I don't use the 200 mm lens any more because I have a Raynox 150, which is about the same strength but better quality.  Good luck with your experimenting.

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dickiedoo
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Re: DIY Add on diopter
In reply to Stephen Barrett, 10 months ago

Stephen Barrett wrote:

Hello dickiedoo,
You can get an approximate measure of the focal length of your closeup lens by focusing a distant scene (eg a tree outside the window) onto a wall and measuring the midpoint of the lens to the wall.

Can you explain that in a different way,I'm not following you

dickiedoo

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dickiedoo
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Re: DIY Add on diopter
In reply to dickiedoo, 10 months ago

I've been playing around with different things and I believe this DIY unit will remain with me. It appears the cloudiness was the relative position of my desk lamp along with some setting changes. This shot of bubbles was done thru the plastic container that holds the lens cleaner solution. The plastic probably contributes to a lesser image quality. This image is direct from the camera except for cropping.The OOF right and left is due to the container starting to curve away and the bottom OOF is the the shoulder of the bottle. I still need to do a lot of playing but I'm satisfied for the moment. The blurred bubbles in the background are about an inch farther(thats the container diameter)

The scratche's/artifact's are imperfections in the plastic container I believe.

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Stephen Barrett
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Re: DIY Add on diopter
In reply to dickiedoo, 10 months ago

Hello dickiedoo,
Good job!
For an approximate measurement of the focal length, just hold your closeup lens close to a wall and adjust the distance until you get a focused image on the wall. Something outside a window will do, or even a lamp on the other side of the room.
The focal length is approximately the distance from the centre of the lens to the wall. You can improve the accuracy by repeating the measurement with the lens direction reversed and then averaging the two measurements. If you want the strength in diopters, that is given by:
diopters = 1000 / (focal length in mm)

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dicklaxt
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Re: DIY Add on diopter
In reply to Stephen Barrett, 10 months ago

Stephen I guess you will have to hit me with a hammer,,,,,,,,this is just not computing,,,,,,,,,

dickiedoo

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Stephen Barrett
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Re: DIY Add on diopter
In reply to dicklaxt, 10 months ago

Hello dicklaxt,

One picture is worth a thousand words:

Closeup Lens - projecting an inverted image onto a wall.

This is a picture of my left hand, holding one of my home-made closeup lenses near a wall. (My right hand is snapping the picture.)  An inverted image of the window at the opposite side of the room is projected onto the wall. You can see an upside-down tree with grass at the top of the image and sky at the bottom. The image of the tree is in focus when the lens is 70 mm from the wall, so that is the focal length. The strength is (1000/ 70) ~ 14 diopters.

It isn't a good closeup lens because it is convex on one side and concave on the other. Like yours, it was scavenged from a camera lens.

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dicklaxt
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Re: DIY Add on diopter
In reply to Stephen Barrett, 10 months ago

Okay got it that time the diameter of this lens is small and it got me up close to the wall before I could see it. I had the right idea just didn't follow up on it .I was about 30mm+ or -, which is 33 diopters,,,,,,,,is that good or bad to work with?

dickiedoo

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Stephen Barrett
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Re: DIY Add on diopter
In reply to dicklaxt, 10 months ago

I think you can have some fun with your diy closeup lens. It is about 4 times stronger than your Raynox 250, which is 8 diopters. You get the most magnification when using full optical zoom of your SX50. The magnification is approximately the ratio of the camera's focal length to the closeup-lens' focal length. So for full optical zoom, you will get 215 mm / 30 mm ~ 7 x magnification, which is huge. If you take a photo of something 1/2 mm high, the image on the sensor will be 7 times that, or about 3.5 mm high. The sensor height is only about 4.5 mm, so you will nearly fill the picture height. The "macro" setting on the SX50 has only about 0.2 magnification up close to the lens. (Macro has traditionally meant a magnification of 1 for SLRs but, if you take into account the crop factor of small-sensor cameras, the effective magnification is around 1, so they call the setting "macro". That would make the "effective magnification" of your home-made lens approximately 40x ! )

The drawback to having so much power is that the depth-of-field is very small - I would guess ~ 1/10 mm at full zoom. The EXIF data on your bubble picture says 36.54 mm, so you can get about 6X more magnification than that.

My experience has been that even the Raynox 250 is so strong that I use it mostly indoors on a tripod , but other people post really good pictures in this forum, taken hand-held, but usually with much less than full zoom. For flowers and insects outside, I most often use my home-made 600 mm closeup lens (made from the front lens of a cheap telescope). Canon makes a 500 mm (2 diopter) lens, which is just a little stronger. Besides greater depth-of-field, another advantage of weaker closeup lenses is that the working distance (equal to the focal length of the closeup lens) is larger, so it is easier to avoid casting a shadow on your subject and to avoid scaring away insects.

Anyway, I hope you play around with your home-made lens and show us some spectacular pictures.

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dicklaxt
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Re: DIY Add on diopter
In reply to Stephen Barrett, 10 months ago

It's pretty obvious I'm flying by the seat of my pants with all of this,,,,,,,,,I'll probably have more fun trying to learn than I will in posting pic's. I've found in a studio setting which I'm kind of limited to that IQ goes south very quickly if the lighting of the subject isn't addressed at the same time other adjustment's are being made,unfortunately a lighting set up I don't have either so need to try and get that rectified.

Thanks for the help

dickiedoo

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