A reasonably priced lens, with potential

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MichaelG.
Posts: 3976
Joined: Mon Apr 10, 2017 8:24 am
Location: North Wales

A reasonably priced lens, with potential

#1 Post by MichaelG. » Mon Jun 21, 2021 7:37 am

This looks quite promising, if you have a spare C-mount camera and want a macroscope :
https://www.ebay.co.uk/itm/142420261284

15:1 Zoom range … not sure what sensor size it covers though
[there are clues in the ebay description … just need to do some sums]

MichaelG.
.
Edit: __ As the interested reader should have noticed, by now
There are discrepancies between the claimed ranges for field of view, zoom, and magnification
Working distance: 120mm-500mm
Field of view: 12mm-50mm
zoom c-mount Lens
zoom ratios: 15:1
Magnification Power by 0.1 - 0.8X (about 10 - 80X on the display)
Size: 60mm(L) * 50mm(DIA)
With 50mm ring adapter
I may ask the Seller, but meanwhile … can anyone reconcile the numbers ?
Too many 'projects'

MichaelG.
Posts: 3976
Joined: Mon Apr 10, 2017 8:24 am
Location: North Wales

Re: A reasonably priced lens, with potential

#2 Post by MichaelG. » Tue Jun 22, 2021 9:22 am

UPDATE :

I wrote to the seller, and have received two well-intentioned but basically meaningless replies.

On that basis … it still looks ‘interesting’ but I cannot recommend it.

MichaelG.
.

Transcript, for info.
Hello,

This is just a lens, in fact if you test by different camera, you can get different result...

In fact for this lens, you can get very good image on the monitor....

Thank you~
AK Wang
Any Questions Please email us
Thank You so much!
Have a wonderful day/evening
The Team at lapsun
lapsuntech(at)gmail(dot)com;


Reply
Your previous message

Thank you for the prompt reply
Yes, I understand that C-mount and CS-mount will require different working distances.
.
Sorry … it seems that I did not express my question clearly

Zoom is stated as 15:1 … ( ratio 15 )
Field of view is stated as 12mm to 50mm … ( ratio 4.16 )
Magnification is stated as 0.1 to 0.8 … ( ratio 8 )

But for a specific lens and sensor, these three ratios should all be equal

Could you please clarify ?

MichaelG.
lapsun_gift:

Hello,

Thanks for your inquiry.

If your camera is C-MOUNT, the max working distance is about 500mm, depends on the your camera....

If your camera is CS-MOUNT, the max working distance should be longer....

If you have any inquiry please let us know.

Thank you~!
AK Wang
Your previous message

I am interested in the lens … but confused by your specification:

There are discrepancies between the claimed ranges for field of view, zoom, and magnification

Working distance: 120mm-500mm
Field of view: 12mm-50mm
zoom c-mount Lens
zoom ratios: 15:1
Magnification Power by 0.1 - 0.8X (about 10 - 80X on the display)
Size: 60mm(L) * 50mm(DIA)
With 50mm ring adapter

I would be most grateful for clarification.

MichaelG.
Too many 'projects'

Hobbyst46
Posts: 4277
Joined: Mon Aug 21, 2017 9:02 pm

Re: A reasonably priced lens, with potential

#3 Post by Hobbyst46 » Tue Jun 22, 2021 11:58 am

Just some thoughts based on the two photos of enlarged ruler marks in the "full description" section of the seller's site:
I assume that his PC monitor is 50cm wide.

From which I estimate that the object-to-lens distance (OD) is 50cm in the bottom photo (where magnification is lower) and 12cm in the top photo.
I take that magnification as the ratio between the monitor size and the selected ruler section size,
so 50cm/5cm=10x and 50cm/1.3cm=38x mags, respectively.

I use the expression OD=f((1/m)+1) where f is focal length and m is magnification. This gives f values of 45 and 12, respectively (approximately).

So it is indeed a zoom lens that, in this case, if we believe the seller's photos and my own assumption and guesses, has a 1:4 zoom ratio.
The seller probably factored in some unknown sensor data to reach the 15:1 level.
FWIW.

MichaelG.
Posts: 3976
Joined: Mon Apr 10, 2017 8:24 am
Location: North Wales

Re: A reasonably priced lens, with potential

#4 Post by MichaelG. » Tue Jun 22, 2021 2:39 pm

Hobbyst46 wrote:
Tue Jun 22, 2021 11:58 am
… So it is indeed a zoom lens that, in this case, if we believe the seller's photos and my own assumption and guesses, has a 1:4 zoom ratio.
The seller probably factored in some unknown sensor data to reach the 15:1 level.
FWIW.
.
Thanks for that … we are thinking along the same lines
I think the most reliable part of the ‘specification’ must be
Field of view: 12mm-50mm
… and the other numbers are just ‘advertising puff’

MichaelG.
Too many 'projects'

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