Go to advanced search

by rkinch
Fri Jun 07, 2013 9:38 pm
Forum: Camera board
Topic: Camera focus distance and macro lenses
Replies: 71
Views: 57802

Re: Camera focus distance and macro lenses

If you tape or otherwise attach this fine bit of well-corrected optics to the front of the camera module lens, it will make an excellent close-up lens: http://www.surplusshed.com/pages/item/pl1047.html This specimen is an f=25mm lens, which is to say, it will present objects 25mm from the lens as if...
by rkinch
Fri Jun 07, 2013 9:13 pm
Forum: Camera board
Topic: Flash sync possible with the camera module?
Replies: 14
Views: 8714

Re: Flash sync possible with the camera module?

Actually, I don't think the sensor flash sync is wired up. It would have to be done from the GPU ... I'll take a look at the codebase when time allows to see if there is anything that could be leveraged which might save some time. Yes, thank you, I am intensely curious about your analysis of the de...
by rkinch
Fri Jun 07, 2013 7:35 pm
Forum: Camera board
Topic: Flash sync possible with the camera module?
Replies: 14
Views: 8714

Re: Flash sync possible with the camera module?

Tell you what - when everyone stops whining and whinging about their particular requirements, I might consider actually doing more work on the camera. But since I spent a lot of spare time working on the software as is, and it's an never ending stream of 'tragic', 'broken', 'fail' and similar comme...
by rkinch
Fri Jun 07, 2013 5:00 am
Forum: Camera board
Topic: Variant characterizations of the camera module lens
Replies: 39
Views: 10583

Re: Variant characterizations of the camera module lens

I've retracted my earlier measurements which were in error and made new ones that agree with the other posters, yielding a lens characterization of f=3.6mm f/2.9. Seems like we have a consensus for those numbers.

Please see my edited original post at the top of this thread.
by rkinch
Fri Jun 07, 2013 1:44 am
Forum: Camera board
Topic: Variant characterizations of the camera module lens
Replies: 39
Views: 10583

Re: Variant characterizations of the camera module lens

Speaking of which, am I imagining things or does the lens look weirdly aspheric from the inside? Why yes, just look at the rear surface, which is a dimpled toroid, like a cervix! I think you're seeing internal reflections from a single element with complex surfaces, with the front being a kind of s...
by rkinch
Fri Jun 07, 2013 1:39 am
Forum: Camera board
Topic: Variant characterizations of the camera module lens
Replies: 39
Views: 10583

Re: Variant characterizations of the camera module lens

What if you measure the angle through which the camera must be rotated for an object at one extreme edge of the frame to reach the opposite edge of the frame? Some tripods have azimuth markings. Yes, goniometry it's called. That's really what you're doing with the yardstick measurements, then deriv...
by rkinch
Fri Jun 07, 2013 12:41 am
Forum: Camera board
Topic: Flash sync possible with the camera module?
Replies: 14
Views: 8714

Re: Flash sync possible with the camera module?

All the flash code is in the firmware, but it doesn't actually know there is a flash there. It would be possible to modify the firmware (not something that can be done by the man on the street) to allocate a GPIO to be set at the appropriate time. That is not going to be done in the near future. Th...
by rkinch
Thu Jun 06, 2013 8:38 pm
Forum: Camera board
Topic: Variant characterizations of the camera module lens
Replies: 39
Views: 10583

Re: Variant characterizations of the camera module lens

If you increase the lens-sensor distance to bring a closer object into focus, then the distance between lens and sensor is no longer equal to the "focal length" of the lens itself. I thought you might have neglected that correction. OK, I see what you mean. Yes, you have to correct for finite conju...
by rkinch
Thu Jun 06, 2013 8:28 pm
Forum: Camera board
Topic: Flash sync possible with the camera module?
Replies: 14
Views: 8714

Re: Flash sync possible with the camera module?

http://www.raspberrypi.org/phpBB3/viewtopic.php?f=43&t=45089#p357425 This does not answer the question. Flash sync has to come synchronously from the chip hardware, which the OmniVision chip provides. You can't program it in software (at least not reliably or with full-speed timing) because there i...
by rkinch
Thu Jun 06, 2013 8:10 pm
Forum: Camera board
Topic: Variant characterizations of the camera module lens
Replies: 39
Views: 10583

Re: Variant characterizations of the camera module lens

Did you adjust the focus of your lens (eg. unscrew the lens element from the stock "infinity focus" position to focus closer, for this experiment? If so, that will change the distance of the lens from the sensor, and therefore the calculated focal length of the lens based on the similar triangles c...
by rkinch
Thu Jun 06, 2013 8:03 pm
Forum: Camera board
Topic: Variant characterizations of the camera module lens
Replies: 39
Views: 10583

Re: Variant characterizations of the camera module lens

... Full-width crop of test image here: http://bealecorner.org/best/RPi/RPi-819mm-HFOV.jpg ... The above measurements imply my lens focal length is 3.650 mm +/- 0.008 mm This technique is not trigonometrically or optically precise. You have to measure the apparent width of something from edge to ed...
by rkinch
Thu Jun 06, 2013 6:15 am
Forum: Camera board
Topic: Variant characterizations of the camera module lens
Replies: 39
Views: 10583

Re: Variant characterizations of the camera module lens

The measurements I made with any level of seriousness were regarding focal length. OK, but could you at least look at my photo above, and at towolf's farther above, and compare to the lens you measured at f=3.6mm? Are they similarly featured with the spline edge? The 2.2mm OD bevel around the pupil...
by rkinch
Thu Jun 06, 2013 12:54 am
Forum: Camera board
Topic: Flash sync possible with the camera module?
Replies: 14
Views: 8714

Flash sync possible with the camera module?

Does the camera module support the OV5647 flash sync feature for still photos? OminVision's documentation says there is "support for LED and flash strobe mode" ( http://www.ovt.com/products/sensor.php?id=66 ). Are the chip details and the camera board and drivers documented in this regard, or propri...
by rkinch
Wed Jun 05, 2013 10:19 pm
Forum: Camera board
Topic: Variant characterizations of the camera module lens
Replies: 39
Views: 10583

Re: Variant characterizations of the camera module lens

I was the one who added the camera info to the elinux wiki site, relying on this post from "fastmapper" who quoted 3.60 mm +/- 0.01 mm http://www.raspberrypi.org/phpBB3/viewtopic.php?f=43&t=32605&start=325#p357018 Right, well, fastmapper's measurements seem credible, so I still do not understand wh...
by rkinch
Wed Jun 05, 2013 10:12 pm
Forum: Camera board
Topic: Variant characterizations of the camera module lens
Replies: 39
Views: 10583

Re: Variant characterizations of the camera module lens

towolf wrote:... this pretty much confirms ~ 1.25mm.
Thanks, nicely done. This lens looks like mine.
by rkinch
Wed Jun 05, 2013 8:16 pm
Forum: Camera board
Topic: Variant characterizations of the camera module lens
Replies: 39
Views: 10583

Re: Variant characterizations of the camera module lens

Don't forget it's a cheap camera with a cheap lens. No, it is not a toy or a cheap gadget, although the price is cheap. This is a sophisticated board-level camera which has a potential to fulfill many applications that have been 10s or 100s of times more costly in the recent past. Applying cameras ...
by rkinch
Wed Jun 05, 2013 6:43 pm
Forum: Camera board
Topic: Variant characterizations of the camera module lens
Replies: 39
Views: 10583

Re: Variant characterizations of the camera module lens

Can you advise how to measure the pupil properly? You can start with just measuring the diameter of the aperture in the front. In general for lenses this may or may not be the actual pupil, but it certainly is an upper bound because nothing further back can enlarge the appearance of the front apert...
by rkinch
Wed Jun 05, 2013 6:39 am
Forum: Camera board
Topic: Stock lens in the camera module 3.6mm f/2.9 [was: 4mm f/3.2]
Replies: 11
Views: 20042

Re: Stock lens in the camera module shown to be 4mm f/3.2

How accurate do you believe your measurements were? Plus or minus a few percent. Not enough to account for 3.6mm vs 4.0mm focal length result. My vertical vs horizontal measurements differed by only 1.2 percent which was my check. Indeed I erred as you suggest in counting dark pixels (extra 32 colu...
by rkinch
Tue Jun 04, 2013 8:45 pm
Forum: Camera board
Topic: Variant characterizations of the camera module lens
Replies: 39
Views: 10583

Variant characterizations of the camera module lens

Update: I stand corrected. After repeating my measurements, I am retracting my original finding of f=4mm for the lens, and agreeing with the f=3.6mm f/2.9 finding that others have made. Here is my original report: My lens measurements and characterization as 4mm f/3.2 at http://www.truetex.com/raspb...
by rkinch
Tue Jun 04, 2013 6:03 pm
Forum: Camera board
Topic: Stock lens in the camera module 3.6mm f/2.9 [was: 4mm f/3.2]
Replies: 11
Views: 20042

Re: Stock lens in the camera module shown to be 4mm f/3.2

towolf wrote:How confident are you about the aperture F-number of 3.2? Another user here had estimated f/2.
Just look at the entrance to the lens. If it were f/2 then the pupil would have to be 2mm diameter. It is obviously much smaller than that. I measure 1.25mm using a 10x reticle.
by rkinch
Tue Jun 04, 2013 6:31 am
Forum: Camera board
Topic: Stock lens in the camera module 3.6mm f/2.9 [was: 4mm f/3.2]
Replies: 11
Views: 20042

Stock lens in the camera module 3.6mm f/2.9 [was: 4mm f/3.2]

After repeating my measurements, I am retracting my original finding of f=4mm for the lens, and agreeing with the f=3.6mm f/2.9 finding that others have made. This is based on a new field measurement of 194.5 inches wide at 195 inches distance, and 38.5 inches wide at 38 inches. Repeating the calcul...
by rkinch
Sun Jun 02, 2013 7:31 am
Forum: Camera board
Topic: M12 lens adapter for camera module
Replies: 80
Views: 79995

M12 lens adapter for camera module

Here is my adapter to use standard M12 board camera lenses with the Raspberry Pi camera module.
Remove the stock lens and attach this adapter to use an M12 lens.

http://www.truetex.com/raspberry_pi_m12 ... dapter.pdf
Image

Go to advanced search