mattfender
Posts: 3
Joined: Wed May 05, 2021 12:59 pm

Real world minimum focus distance for 6mm HQ lens

Wed May 05, 2021 1:10 pm

Hi all,
I am thinking of ordering the HQ camera with the 6mm wide angle lens (or possibly the IR cut version of same, from Arducam). I will be using the camera in a bird nesting box, and have had success over the last few years with both v1 and v2 cameras. One issue with nest boxes is that the space is very confined, and typically the camera is only about 15cm from the "action". The minimum object distance for the 6mm lens is quoted at 0.2m, although in my experience these values are often a little conservative, so it would be really useful for me if someone who already has this camera and lens could confirm a real-world minimum focus distance. I think I could work with 15cm, although even a bit less would be great. The other challenge, especially when focusing close, and with a large aperture setting, is the depth of field - the larger the better. A major issue when setting up these nest boxes is that you have one chance to set focus, aperture etc and then you effectively have to leave it for several months, so a lens that can keep as much as possible in focus, whilst still working well in low light, would be ideal.

Alternatively, if the required MOD with the stock 6mm lens is not going to be achievable, does anyone have suggestions for an alternative lens to fit the HQ camera? The picture below is from this year's nest, using a v2 camera. The FOV is about right for this box, at just over 60 degrees horizontal, so a similar lens would be ideal (slightly wider also acceptable).

thanks!

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CharlyDelta
Posts: 234
Joined: Thu Jul 18, 2013 4:04 am
Location: Near Montreal, Quebec

Re: Real world minimum focus distance for 6mm HQ lens

Wed May 05, 2021 2:52 pm

I have both HQ cameras and I remember doing some close-up testing. With both HQ models, I had managed to get a good focus at 15 cm and still much less, which is adequate for a nesting box. By the way, I have a lot of Raspberry cameras in several nesting boxes but I never had the idea to put a HQ camera because it does not come in a NoIr model. So, all my nesting box cameras are NoIr and equipped with infrared lights so as not to scare the birds and to be able to observe them at night (as I am doing now with a nest of spotted screech-owls). I can always remove the IR filter from the HQ camera but at the price it costs, I'll wait until they come out with a NoIr HQ model. In the meantime, the V2 cameras do a very good job. Go visit this page:

https://nidcornifleur.blogspot.com/2020 ... fleur.html

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nidcornifleur@gmail.com

mattfender
Posts: 3
Joined: Wed May 05, 2021 12:59 pm

Re: Real world minimum focus distance for 6mm HQ lens

Wed May 05, 2021 3:27 pm

Thanks you so much! This is exactly the information I was looking for, and indeed it does seem as if the 20cm specified minimum focus distance is very conservative! How are you finding depth of field at close focus? Do you think it might be feasible, for example, to keep the range 12-20cm in focus? That would be ideal.
Regarding IR cameras, I did use a v1 NoIR camera in the early days (not an IR cut), and although of course I was able to get night time images, the day images were far below the standard that is possible when using an IR filter. An IR cut filter obviously solves this issue, and I did try a third part one of those one year (v1 sensor), but didn't get a nest in that box. I have since decided that, since not much actually happens at night for my target species (bluetit), it is better to run a normal camera with additional LED illumination. I am however quite interested in this IR Cut HQ Camera from Arducam, which came up in a search today. It seems to come with the same 6mm as the regular HQ camera, and Arducam seem like a reputable company(?).
Thanks again!

gordon77
Posts: 5691
Joined: Sun Aug 05, 2012 3:12 pm

Re: Real world minimum focus distance for 6mm HQ lens

Wed May 05, 2021 3:33 pm

You can get a lens to focus closer by use of extension tubes or spacers, which fit between the camera and lens. Look for c-mount.

Jack Hogan
Posts: 116
Joined: Wed May 13, 2020 2:08 pm
Contact: Website

Re: Real world minimum focus distance for 6mm HQ lens

Thu May 06, 2021 9:57 am

mattfender wrote:
Wed May 05, 2021 3:27 pm
How are you finding depth of field at close focus? Do you think it might be feasible, for example, to keep the range 12-20cm in focus?
That's a very hard question to answer because the answer is subjective and those are starting to approach macro conditions. It depends on a very large number of variables, starting with how large you like to look at your images, more here.

gordon77
Posts: 5691
Joined: Sun Aug 05, 2012 3:12 pm

Re: Real world minimum focus distance for 6mm HQ lens

Thu May 06, 2021 10:25 am

You could try using a dof calculator eg https://www.cambridgeincolour.com/tutor ... ulator.htm

I think 1/2.3" is the nearest to the pi hq sensor.
Attachments
dof.jpg
dof.jpg (46.74 KiB) Viewed 276 times

mattfender
Posts: 3
Joined: Wed May 05, 2021 12:59 pm

Re: Real world minimum focus distance for 6mm HQ lens

Thu May 06, 2021 10:41 am

Thank you all. That depth of field calculator is very useful, and suggests that the stock 6mm lens is not going to be too useful for me - I will be limited to a 1cm field at a distance of 15cm and an aperture setting of F1.2. Strange, because I had the impression that the aperture was variable, but looking again at the spec sheet that doesn't appear to be the case. In which case, what does the "open/close" control on the lens actually do? (as distinct from what looks like the focus control). A similar length lens capable of an aperture setting of F8 or F16 should work well, although of course low light operation will be compromised.
I wonder if someone will ever make an auto/remote focus camera for the pi? That really would be ideal.

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CharlyDelta
Posts: 234
Joined: Thu Jul 18, 2013 4:04 am
Location: Near Montreal, Quebec

Re: Real world minimum focus distance for 6mm HQ lens

Thu May 06, 2021 12:39 pm

I got this ''auto focus'' NoIr camera but it doesn't work with Rpi Cam Web, my favorite software for nesting. Apart from this program, I have not really tested, having little interest in this function.

https://www.arducam.com/product/b0190-a ... no-camera/
nidcornifleur@gmail.com

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