The Raspberry Pi Camera is a fixed focus module, so that anything from about 0.5m to infinity is acceptably sharp. This has strengths and weaknesses, as with every design decision. The weakness in this case is that if you want to film or photograph anything closer than about 50-75cm it will be out of focus.
With large SLR cameras, what people do is change the lens for a macro or close-up lens. We can’t do that easily. The other (cheaper, but generally less good) option photographers use is to add a small, screw-in, close-up magnifying lens in front of the existing lens which allows closer focus. This is something we can do…
Adding a +2D lens allows you to focus at about 25cm from the “target”.
For me this is ideal, since I’d like to use a Rapberry Pi Camera as a second video camera to give alternative close-in views in some of my workshop demos. It would also be great for time-lapse shots of small things growing.
What about cheap reading glasses?
Pluggy, over at the Raspberry Pi Forums, suggested using cheap reading glasses.
I was sceptical but tried it.
What I did was shoot some video of my laptop screen close enough for a full-screen shot (probably ~30cm). I did this twice, and grabbed screenshots for the comparisons…
- once for with and without the cheap Poundland +2D glasses
- once for with and without my “proper” +2D camera lens
Here are the results. You will need to click them to see the comparisons at full size. Otherwise you won’t get the full effect…
You can see above that the cheap +2D glasses give great focus, but reduce the contrast a bit. The black computer screen goes a bit grey.
With the camera optic, you can see the focus is great and the contrast is much less affected.
Comparing all four together
Here’s a shot with all four in so you can compare. The reason for shooting the “blank” twice was that different shooting positions affect the results. Ideally this would be done on a tripod, but I have yet to make a tripod attachment for my PiCamCorder
The cheap Poundland +2D glasses give acceptable results, but the “proper” camera optic gives better results at about ten times the price. The “proper” lens is a bit more bulky and inconvenient as well. I love the “hackability” of the Poundland lenses. I could easily cut those up without issue. I wouldn’t want to spoil the camera optic – my precious. ;)
Here’s a little hand-held video showing the live action of the tests. Enjoy…
Here’s all the photos taken in the making of this article. Click to enlarge…