Q on 50X Telescope Zoom Mobile Phone Lens / HQ camera

[HermannSW]

I received 14$ "50X Telescope Zoom Mobile Phone Lens" from aliexpress:
https://www.aliexpress.com/item/32950245167.html

I mounted my smartphone and took a photo of 59m distant street light top.
16MP photo scaled to 10% size for attachment:

20200701_183944.10%.jpg

20200701_183944.10%.jpg (10.82 KiB) Viewed 2150 times

Then I removed smartphone and captured steet light with smartphone as well, here scaled to 10%:

20200701_184016.10%.jpg

20200701_184016.10%.jpg (33.21 KiB) Viewed 2150 times

This is 100% copy out of street light top from both photos, copied together:
(what you see in front of sky in left image is window fly screen)

copy_out.100%.jpg

copy_out.100%.jpg (54.88 KiB) Viewed 2150 times

I did measure front length of street light top as 32 pixels / 291 pixels with gimp measure tool.
That is only factor 291/32=9.1.
So did I get a 9X zoom lens only?
Or is my understanding of "50X" wrong?

Second question, if I put that lens in front of HQ camera with some lens, will I get factor 9X better magnification as well?


P.S:
If possible, I want to get 9.1X for 35mm lens:
viewtopic.php?f=43&t=272658&p=1674607#p1674607

[HermannSW]

I can answer my 2nd question from yesterday, and the answer is YES, zoom lens can be combined with 35mm HQ camera lens!

First I took a comparison shot with 35mm lens only.
Then I did a shot (raspistill -o 35mm.zoom.jpg) with 35mm lens plus zoom lens.
Then I created a 100% copy_out for both as yesterday.
I measure 223 pixels for 35mm lens only (less than smartphone plus zoom yesterday, but 7× more than smartphone only).
And I measured 1799 pixels(!!) for street light top length for 35mm plus zoom.
That is a factor 1799/223=8.1 -- not 9,1 as yesterday, but wow anyway.
The different look of both photos is most likely caused by different aperture settings of 35mm lens for both photos.
Here is 100% copy_out (2844x1944):
https://stamm-wilbrandt.de/en/forum/zoo ... .100pc.jpg
And here is that image scaled to 20% size:

copy_out.20%.jpg

copy_out.20%.jpg (19.42 KiB) Viewed 2069 times

This was the setup, 35mm lens with HQ camera does wheigh 109g, zoom lens does wheigh 279g.
So I used tripods for both, and cardboards to fit the difference:

20200702_194649.15%.jpg

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Here you can see the settings used, and that the lenses do not even have to be perfectly in line!

20200702_194759.15%.jpg

20200702_194759.15%.jpg (42.15 KiB) Viewed 2069 times

So question 1 from yesterday needs an answer still -- zoom lens gives 9.1× for smartphone, and 8.1× for 35mm lens wrt length measured.
What does 50×-60× rating of zoom lens mean?
On last photo the label for zoom lens is "50x60" and "1500M|9500M" ...

[gordon77]

With binoculars etc you get a figure like 10×50. The first number is their power (or magnification) and the second is the diameter of their lenses.

[HermannSW]

With binoculars etc you get a figure like 10×50. The first number is their power (or magnification) and the second is the diameter of their lenses.

Thanks, so 50 ×magnification, and 60mm lenses.
Still question remains how "50× magnification" relates to measured length factors of 9.1× and 8.1× ...


The 35mm C mount lens has horizontal Field Of View (FOV) 10°:
https://www.uctronics.com/arducam-10-de ... amera.html

I think this is how to calculate the combined 35mm lens plus zoom lens horizontal FoV.
It is 1.24°(!), far less than previous minimum 3.98° of my 70mm lens:

Code: Select all

L = (4056/2)/tan(10°/2) = 2028/tan(5°)
tan(α/2) = (2028/8.1)/L = 250/L = tan(5°)*250/2028 = tan(5°)/8.1
α = 2*atan(tan(5°)/8.1) = 1.24°

[ethanol100]

Marketing? It just has less then 10x, as you have measured, but 50x sounds better?
Anyway, what do you expect from a 14$ optical device?!

You also need to take the F-Number into account, you would effectively hav a 50x bigger focal length and a 50x bigger f-Number. If you had 1.4 for the 35mm lens you would end up with 52, which basically means you could get hardly any light onto the sensor.

[HermannSW]

Marketing? It just has less then 10x, as you have measured, but 50x sounds better?
Anyway, what do you expect from a 14$ optical device?!

Thanks for confirming that what I thought and read about maginification
https://en.wikipedia.org/wiki/Magnification
is correct and I "only" got 8.1× zoom -- but I am totally happy with 8.1× zoom for only 14$.

You also need to take the F-Number into account, you would effectively hav a 50x bigger focal length and a 50x bigger f-Number. If you had 1.4 for the 35mm lens you would end up with 52, which basically means you could get hardly any light onto the sensor.

You have seen street light lamp in previous posting, and that looks OK for me.
I just captured a small tower 2.3km distant with HQ camera plus 35mm lens with zoom lens in series -- 700x1116 pixels!
viewtopic.php?f=43&t=272658&p=1689751#p1689751

Last night I wanted to capture moon, but more and more clouds did not allow for that.
This is 348 pixel diameter moon captured with 35mm lens alone (12MP photo scaled to 15% for attachment):
https://twitter.com/HermannSW/status/12 ... 7488374785

tst5.15%.jpg

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Full moon will be on Sunday, and forecast says that tonight will be a clear night.
In case magnification will keep to be 8.1×:
8.1*348=2819 pixels will be diameter of moon, that is 70% of horizontal and 93% of vertical size of 12MP 4056x3040 photo(!).

On the other hand I read that moon diameter is 3476km, and current distance from earth to moon is 372,523km.
I calculated yesterday that effective horizontal FoV of combined 35mm and zoom lens is 1.24°.
With the numbers of moon I calculated moon to cover 0.53° -- will see what I will get tonight:

Code: Select all

2*atan((3476/2)/372523)=0.53°

[ethanol100]

You had asked in another thread, if I could provide images with the 250mm lens, but as the view from my flat is quite limited, I took the camera outside and captured a series of images with different lenses.
The target was a about 6km away. It is Colonius, the Cologne telecommunications tower. We can look at the height of the three story platform, which is 14.7m. With different lenses I get the following resolutions:

Code: Select all

6mm -> 11px (6mm CS-mount lens)
12mm -> 27px (12mm C-mount lens)
55mm -> 114px (55-250mm Canon lens)
250mm -> 391px (55-250mm Canon lens)
500mm -> 836px (500mm mirror lens)

The images can be found on google drive.

[HermannSW]

You had asked in another thread, if I could provide images with the 250mm lens, but as the view from my flat is quite limited, I took the camera outside and captured a series of images with different lenses.

Thanks for doing this, and for the different numbers and photos.

I copied together 100% the top of tower from your 5 photos, and finally scaled combined image to 15% -- impressive to see the differences:

all.15%.jpg

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[HermannSW]

First photo of moon with 35mm lens and zoom lens in series, moon behind tree 50m distant.
I measured diameter in 12MP photo between 1800 and 1900, so smaller than the 70% calculated.
Perhaps these values match the 0.53° calculated.
Moon will enter free of trees area soon, and currently sky is dark and clear.
I even saw stars through just the zoom lens with my eyes.
https://stamm-wilbrandt.de/en/forum/moon.1.jpg
Scaled to 15%:

moon.1.15%.jpg

moon.1.15%.jpg (12.25 KiB) Viewed 1822 times

[HermannSW]

This seems to be real, 12MP photo here:
https://stamm-wilbrandt.de/en/forum/moon.2.jpg

Cut out 2060x2016 part, scaled to 25%:

moon.2.part.25%.jpg

moon.2.part.25%.jpg (30.66 KiB) Viewed 1799 times

I will have to play more, I get much sharper structures on moon when playing with aperture, but then I don't see full moon although currently we have near full moon ...

[HermannSW]

12MP photo captured with letting in minimal amount of light via aperture ring of 35mm lens.
https://stamm-wilbrandt.de/en/forum/moon.3.jpg
1700x1700 copy out, scaled to 40%:

moon.3.part.40%.jpg

moon.3.part.40%.jpg (57.67 KiB) Viewed 1768 times

I did capture video as well, see ""Re: HQ Camera Moon video test":
viewtopic.php?f=43&t=273590&p=1690223#p1690223



P.S:
Changed lens settings a bit, sharper photo:

moon.4.part.40%.jpg

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P.P.S:
It was not easy to get image sharper.
While there is only one aperture ring at 35mm lens, manual focus has to be done for both lenses.

[HermannSW]

I did buy another 14$ "50X" smartphone zoom lens.
I tried to use both zoom lenses with 35mm C mount lens in series.
Magnification really became much better, but image quality became really bad:
viewtopic.php?f=43&t=272658&start=175#p1699813

So for capturing moon better lens / telescope is needed,
Anyway, did capture 84% moon tonight with single zoom lens in series to 35mm lens.
The 2nd zoom lens was helpful in just looking through with my eyes to compare what got captured to what I see.
What I see with my eye through zoom lens is so much better quality.
I did focus with raspistill's "--focus" option, it turned out I had to move lens to most FAR position.
I did use minimal aperture (1.7) since moon is bright enough.
I did cut out 100% part from 12MP image captured, below you see 40% scaled.
At the bottom side wide craters can be seen this time more clearly than last time:
https://stamm-wilbrandt.de/en/forum/moon.84pc.part.jpg

moon.84%.part.40%.jpg

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