Does anyone here have a dome/paperweight magnifier they could try an experiment for me?

jsmoove · Mar 15, 2020

Haven't been able to find one yet where I am.
Need to see what it looks like with a mobile phone in direct contact with the magnifier.

jimgalli · Mar 15, 2020

If you have an old condenser enlarger, take one of the "lenses" out of the condenser section.

jsmoove · Mar 15, 2020

@jimgalli No enlarger on hand either unfortunately

flatulent1 · Mar 15, 2020

You didn't say what view you wanted. Does this help?

jsmoove · Mar 15, 2020

@flatulent1 Hi! I was wondering if one could focus through the dome magnifier itself, on your table for instance. So phone camera touching the top of dome magnifier, bottom of the dome magnifier touching the table

jsmoove · Mar 15, 2020

@flatulent1 I'm basically wondering if the dome magnifier shortens the phones minimum focus distance or not/whether or not your table will be in focus, if the phone lens is touching the magnifier

Sirius Glass · Mar 15, 2020

Take a 35mm or 50mm lens off a 35mm camera, open up the lens, look through the front of the lens ===> now you have a magnifier lens.

jsmoove · Mar 15, 2020

@Sirius Glass Thanks....im specifically curious about a dome magnifier however..just need to see what it looks like through it with a mobile phone camera.

flatulent1 · Mar 16, 2020

This will be interesting. My phone has two lenses. My phone is also a few years old and I rarely use the camera on it. It's close-focusing capabilities may not be up to today's standards. I don't have access to the magnifying dome at the moment, but I do have a LensBall (TM) that is about the same diameter but twice the depth. I placed it on my khaki bathrobe, lined up the correct lens, and took the shot. It does focus at least THAT close. I can't upload the photo because I need to resize the image and can't figure out how to do it on my bloody phone. I'll try again in the morning with the magnifier.

I can't believe lightroom mobile doesn't have a 'resize' feature. I guess it's time to crack open that bottle of Irish whiskey.

AgX · Mar 16, 2020

I never came across a dome magnifyer, but optically it is just a plano-convex lens, though with very short focal length.
But camera attachment close-up lenses optically are that too, though with larger focal lengths.

jsmoove · Mar 16, 2020

@flatulent1 What kind of phone is it? I think most mobile phones have a minimum focus distance of around 7-10cm.
Was wondering if the dome magnifier (or your lens ball) cancels out this distance and you are able to focus instead the distance that is instead the physical height of either lens....so alot less than 7cm, depending on how tall your dome magnifier and lens ball are.
Khaki bathrobe and Irish whiskey....snazzy!
@AgX So does a dome magnifier reduce a phones minimum focus distance then when in contact with the phone lens?
That's what I'm hoping for, to focus on the flat or bottom side of the magnifier used.
I've probably mentioned it a few too many times here....I just never actually got to see what it'd look like visually

AgX · Mar 16, 2020

jsmoove said:
So does a dome magnifier reduce a phones minimum focus distance then when in contact with the phone lens?

Basically any convex lens would do so.

flatulent1 · Mar 16, 2020

My phone is an LG G5. The magnifier is about 5.5 cm tall. First shot is through the magnifier with the lens resting on the magnifier. Second shot was taken when I removed the magnifier from under the phone.

jsmoove · Mar 16, 2020

@flatulent1
Thankyou!
So it seems indeed that a dome magnifier does indeed decrease the minimum focus distance of the phone, as the desk looks somewhat in focus.
Do you know the magnification of your dome magnifier? I guess its one of those 2" x 2" dome magnifiers?
Would it be possible to get a picture of something with alot of detail, like a picture in a magazine/piece of film, instead of the table?

flatulent1 · Mar 16, 2020

First shot through the magnifier
Second shot without.

jsmoove · Mar 16, 2020

@flatulent1 Perfect, thanks for the help. Seems to be in focus and there are some details too, horah!
@AgX So basically the dome magnifier works to reduce the minimum focus distance because of its short focal length?

jsmoove · Mar 16, 2020

@flatulent1 If you ever get the time I would love to see a piece of film if you have one (35mm?) under the magnifier in the same scenario. Also, is the magnifier you have something like 2x...or is it more, whats the brand? My goal was to try and see if a dome magnifier could be used as a larger "stanhope" magnifier of a photograph, where the image is pasted on the bottom. You'd have to hold it up to a light source/or light table though I reckon. Thanks for the pictures, you've confirmed my suspicions.

jsmoove · Mar 17, 2020

@AgX Is there a formula for determining the relationship between the dome/convex lenses physical thickness, and how much it reduces minimum focus distance, if the diameter remains the same?

AgX · Mar 17, 2020

What matters is the radius of the convexity.

The basic formula for a planoconvex lens is:

Diopter = (refr. indexair - refr. index lens) / radius of convexity

At a true dome lens: radius = thickness

BAC1967 · Mar 17, 2020

I just tried this with a lens from a condenser. I'm not sure what the condenser came from, probably an old magic lantern projector. Putting my iPhone 8 up against the flat side of the lens didn't seem to do much as far as magnification goes. Putting it against the curved side increased the magnification. The closest I could get using the flat side was about 9 centimeters, it was the same with or without the lens. I could get about 4 centimeters with the curved side. The first photo of news print is with the camera against the flat side, the second is no lens and the third is with the lens against the curved side.

jsmoove · Mar 17, 2020

@BAC1967 Awesome, thankyou! Just google'd the Iphone 8 minimum focus distance and it's 6cm. So you're saying that the condenser is 4cm in thickness then yes? If thats the case, then it reduces the distance by 2cm roughly. The last picture looks pretty in focus. Reading about the stock market crash?

jsmoove · Mar 17, 2020

@BAC1967 You have it like this right? https://imgur.com/a/bgKv17G

BAC1967 · Mar 17, 2020

jsmoove said:
@BAC1967 You have it like this right? https://imgur.com/a/bgKv17G

No, I lifted the lens and camera holding them together until the image was in focus. It's way out of focus if I left the lens against the paper. That is how I had the camera against the lens on the last photo.

jsmoove · Mar 17, 2020

@BAC1967 Ah. Thats what I was curious about. Having the magnifier on the paper, and then the phone touching the magnifier. If its out of focus I guess that means that it can't reduce the minimum focus distance of a phone after all....hmmmm :-/

jsmoove · Mar 17, 2020

@BAC1967 So you were saying that the distance between the bottom(flat side) of the magnifier and the paper was 4cm then? https://imgur.com/a/udQJOO6

Basically, my goal is https://imgur.com/a/bgKv17G where the image would be in focus in this scenario. With the thickness of the lens is less than the minimum phone distance of the phone. (6cm)
I am unclear what type of lens I need to accomplish this..

Does anyone here have a dome/paperweight magnifier they could try an experiment for me?

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