Photosynthesis photography: Making images with living plant leaves

today on applied science I'd like to show you this technique of making images on living plant leaves so the idea is that we pattern light falling on a plant leaf and those regions that receive more intense light will perform photosynthesis more quickly generating more energy for the plant at that location and if the plant has excess energy there it will store this in a starch granule which we later stain with iodine staining the starch blue black which is what creates the image I first saw this technique in a Royal Institution video shot originally in the 1970s but only recently uploaded to YouTube in the last couple years and I completely fell in love with it and wanted to see how far I could take this technique so I started off at what I call level one difficulty which is printing out line art on your printer and using that as a photo mask to make these Leaf Prints but I noticed that you could get really really good resolution I did some resolution tests and when the leaf dries it shrinks and you get sort of a resolution boost I also did some gradation tests and realized that we could reproduce an image with grayscale if you control the exposure well enough and moved on to 35 millimeter film negatives and printed images again from the printer but using grayscale or at least you know half toning sort of um I call that sort of level two difficulty then I also wanted to see if I could make a print from a leaf negative a leaf print from a leaf negative and even that worked actually much to my surprise even though the contrast isn't very good it's cool to show that this technique is sort of just like real photography where you can make negatives and positives and things and then just to be extra meta I took a picture of a leaf and made a leaf print of itself using its own biological Machinery which I kind of got a kick out of but really where we went ahead the ultimate difficulty is making an original photograph and so I made a custom purpose-built camera lens very fast very large camera lens and made an original Photograph by focusing an image down onto the plant leaf and then developing it in iodine I'm completely surprised this worked I I really didn't think that was going to do it and the image is just barely there but if I invert it and play with the levels a little bit the Shadows suddenly makes sense and your brain fills in the details it actually looks like a pretty cool photograph so I replicated this twice just to make sure it wasn't a fluke and figured out that we can't make it much darker and I'll get into the sort of the physics or maybe even the biology of why that's the case and it's a really cool technique that you should try out yourself it's fun to play with and great for you know grade school or kids and stuff too because the chemicals are mostly pretty safe all right let me show you the details let's start with the choice of plant that you're going to use for these experiments if you watch the Royal Institution video or any other online resources they pretty much all suggest to use this plant called a geranium and there's a really good reason for that the leaves are nice and large and they're very delicate so it's easier to get the chlorophyll out and the iodine in when it's time to develop it without disturbing the starch granules these are also very plentiful at least where I am in Northern California pretty much every you know Home Center has a bunch of these for sale so I didn't spend a lot of time optimizing the plant selection I focused more on like the physics and exposure of this whole thing but I did test a couple other things I have a plum tree in my yard and an acacia tree and these two trees send up shoots out of the ground and produce very young leaves that are delicate enough to do this and I tested those as well and found them to perform about the same as a geranium but the problem is they're just too small next we need a way to hold the leaf flat and hold what we're going to expose either our film negative or our print out on top and so I built this sort of a holder here and it's just quarter inch hardware cloth as they call it although it's really just a metal mesh that you can get at a hardware store and two welding rods that are soldered to it and this gives it some more strength so that it'll hold the leaf flat when we put some pressure on it it actually does take a fair bit of clamping pressure to make sure that the leaf is flat with the thing that we're going to pattern the light with if there's any gap between the photo mask and the leaf it will you know lower the resolution and just make it not for a very good result so I was originally very concerned about light getting in from the back side and so I used some of this adhesive really dark felt from Amazon and used this as the backer so we put it together like this with the mask on top and then another piece of about millimeter and a half thick acrylic on top of that and a binder clip to kind of cinch the whole thing together and you know I usually did four binder clips to get enough pressure on there and this did work pretty well but occasionally I would run into a situation where I thought the thing had plenty of exposure and I still didn't get an image and so I started kind of looking into this a little bit more and one problem with this felt is that it has an adhesive layer that's pretty well sealed and remember that one of the inputs into photosynthesis is carbon dioxide if you you could give a leaf as much light in the world and without any carbon dioxide it's not going to perform photosynthesis and since the front of this necessarily how us to have a fairly solid thing across it the CO2 is not going to diffuse through this printout or the hard plastic very well and if we're also sealing the backup with this adhesive layer uh there may not be enough gas exchange to actually get photosynthesis done so then I ripped off the felt layer and tried some other things this is like an old threadbare t-shirt material and it is indeed more permeable than the felt but occasionally I still had problems with not getting a proper exposure and felt like CO2 starvation was still the issue not positive about it but I think that's what it was So eventually I just took it off all together and just went with just the metal hardware cloth and would put this on here like this and then built the whole stack up and just left it open on the back and it's you know it's tilted like this so the sunlight is coming down from the top and I I didn't really have a problem or I don't think it was a problem getting too much light from the backside in general most of these plants are underexposed so if there really was a problem with light leakage coming from the back it wasn't apparent in my in my results another thing that you'll often hear if you read stuff about making these plant prints is that you should put the plant in a dark area to destarch the leaves for two days and then make your print by Shining Light on it this has a lot of problems if you are experimenting with this and you want to make a lot of prints after spending two days in total darkness the plant really has to be put back into light or it will become unhealthy and by unhealthy I mean not only might you lose the plant but it's photosynthesis will slow down to the point where you can't restart it immediately there's like a lot of biological processes that you want to keep idling without shutting down entirely and so don't I found that trying to keep the plant in darkness and then suddenly getting all the prints done and then having it in the light for a few days and then back in the darkness is just too complicated and it doesn't help at all really the easiest thing to do is to just keep the plant outdoors and put your image on there and just leave it for a few days and what will happen is the parts of the leaf that are in the dark will become destarched and the ones that are getting light will continue to be starched and so really all we're looking for is a contrast we don't really care if we're removing sections of starch from the dark areas or adding starch from the light areas it's just the contrast we're after so I found this whole thing about keeping the plant in the dark is is really just counterproductive these geraniums are full sun plants so they can be in direct sunlight for most of the day so conveniently the exposure is bounded on the low side by about 48 hours to give the starch enough time to be consumed in the dark areas and the upper end of the exposure is actually bounded by how many hours of sunlight you get per day like I say most of the problems are under exposure so really you want to put this thing in the brightest spot you've got and currently it's late summer in Northern California so pretty much the ideal time to be doing this I've actually played with this technique off and on over the past year or two and yeah if if you're in Winter conditions you might need artificial light or heating to get the plant active enough to make this work the leaf should be harvested and developed right away at the end of the photo period so right after the direct sunlight is no longer falling on the leaf that's the late afternoon would be the best time to do this it's a really bad idea to harvest in the morning because the leaf has just spent the last you know 12 hours in the dark and you won't get as good of a contrast the development process is two steps the first step is to remove the chlorophyll from the cells the green pigment from the leaf and we do this by boiling it in alcohol for about eight minutes uh if you read all the online resources they'll say you have to use ethanol pure 100 ethanol which is pretty difficult to find and so I thought ah it's probably the same you know any old alcohol would work so I tested it I tried methanol ethanol and isopropanol and found that they perform very differently surprisingly so from left to right this is methanol ethanol and isopropanol so the bad news is that isopropanol is the easiest thing to find and it doesn't work very well and methanol performs the best but it's more toxic than the others so it's kind of literally a case of picker poison and ethanol is very expensive and difficult to get so I I found some references that claim boiling methanol really isn't that bad just make sure you've got good ventilation going or find a source of ethanol and I think I can put one in the description there I found that using a tall form Beaker is really beneficial because the alcohol vapor condenses and goes back down into the liquid so if you're processing a bunch of leaves you can keep this thing boiling for a quite a while half an hour an hour and get a bunch of leaves done I also found that the alcohol becomes saturated with chlorophyll relatively quickly and needs to be changed every three or four leaves anyway after the eight minutes when the leaf comes out of the alcohol it's surprisingly crispy and delicate and so most of the water has been removed because we just boiled it in anhydrous alcohol so to get it softer again and easier for the iodine to get into the cells we just put it in water for a few minutes to rehydrate next we take the hydrated leaf and put it into iodine now we use lugol's iodine solution which is a mix of potassium iodide and Elemental iodine one thing to watch out for if you search Amazon or probably modern drugstores for iodine you'll find this stuff called povidone which doesn't work it's something else and annoyingly it will kind of work and you'll think you're doing something wrong in the process but as it turns out it just doesn't work for this you need to use lugol's iodine solution another thing to avoid is iodine tinctures which is basically lugul's iodine solution with alcohol added and in this case the alcohol is not beneficial for the development of the starch granules if you're really interested in this Leaf print technique I'd recommend investing in a large bottle of lugul's iodine solution it's much much less expensive if you buy it in a large bottle and you'll find that getting even prints consistently requires submerging the whole Leaf just using the little dropper bottle you know it works but it it's if you're going for maximum reproducibility and consistency go for full submersion in a high quality luggles iodine solution I found that there isn't really much control over the development process itself you basically put it in the iodine and wait for the process to complete as far as it's going to go in theory you can pull it out quickly and stop the development process just like you would with black and white photography but again overexposure is almost never a problem in my experience and another issue is that the leaf is so thick that by the time the iodine starts diffusing in there you can't really stop it it is no real easy way I think if you timed it out and you had a really consistent leaf and a really consistent exposure you could dip it in the iodine for a known amount of time and then take it out and put it in water to stop it but in my experience you basically just develop it as far as you can go and then adjust the exposure to work with that after the development is complete I take the leaf and put it in clean water just to get as much iodine back out of the leaf as possible and that's it the image is there if you want to preserve it you can dry the leaf and that's also pretty straightforward I found that just pinching it between filter paper is a great way to do this very simple and easy the trick is you have to use paper that is starch free so filter paper Works test the paper with the iodine solution to make sure that you aren't getting starch from the paper back into your Leaf if you try using like copy paper or binder paper it's going to turn black instantly it's not going to work at all now if you're looking for the highest resolution I mentioned that when you dry the leaf with Filter paper just in air it shrinks quite a bit this might be one case where shrinkage is actually a good thing if you're going for maximum resolution but I was also interested in trying to preserve the leaf without a shrinkage also it darkens quite a bit when it dries in air and I thought there might be a better way so this being applied science I of course went to Super critical drying and got out my CO2 chamber and put a leaf in there and started filling it with liquid CO2 and the idea is that we're going to raise the temperature and make the liquid make the CO2 inside go super critical and then we can let the CO2 out in the supercritical phase and therefore we get rid of the water without ever having it dry normally I was doing this late at night and maybe didn't tighten the bolts down as carefully as I should have and it managed to capture an incident on camera the seals explosively decompressed and I caught some shrapnel probably mostly dry ice sort of a weird injury because it felt so cold I mean literally an Arctic blast that I could feel on my arm anyway not too bad and I think the initial failure mode might have been a crack in the glass that allowed the seals to start expanding and then moving out through the gap uh but anyway the leaf itself unfortunately disappeared it just turned into powder and just completely is gone so undeterred I happen to have another glass window in stock and put that in and got another Leaf in the chamber and started up again I went through the whole process but now it was even later at night and I I it didn't dry even though I got through the whole cycle without shrapnel this time it just didn't dry the leaf very well and I didn't think the technique was very transferable so an even better way to do this is to just take the leaf when it's mostly dry like padded dry with cotton and put it in your freezer this will freeze the leaf obviously and then it won't shrink but the freezer will also freeze dry it and that will produce a flat leaf that looks pretty good and doesn't have quite as much of the shrinkage or darkening as air drying does let's talk about the camera lens that I built to capture the image of my old truck initially I started with this commercially made projection lens and it has about a hundred millimeter focal length and around 100 millimeter entrance pupil so it has an F number of about one which is quite fast in photography most camera lenses are F 1.4 and above so I tried this and it had a couple problems one the the image is just too small I need to fill up the whole geranium leaf and this thing really produces an image that's only about 20 or 30 millimeters in diameter and another problem is it's just not fast enough and like I say you know doing longer exposures doesn't work you really need intensity High sunlight intensity to get enough photosynthesis happening for the plant to start storing the energy as starch it doesn't work to just stretch it out over days so what do you do well you can put a magnifier in front of the lens and that will increase its entrance pupil literally the definition of you know entrance pupil is how big the aperture appears when you're looking into the end of the lens so if you just put a magnifier in front of it that's a bigger entrance pupil more light can find its way into the aperture and make its way to the focal plane it also changes the focal length of the lens and so you have to play with the distance and everything but that's basically the idea that I used to make this lens it's a fresnel lens in the front and a single Glass lens in the back and I played with the distance between these to get about the focal length that I wanted and as it turns out the effective focal length of both lenses in conjunction is also around 100 millimeters but the entrance pupil is about 200 millimeters so this has an F number of 0.5 an extremely fast lens it's about I think three stops faster than an F 1.4 and it's just good enough I mean you saw those images of the truck it it works but it if it were even faster it would be even better and so I kind of almost got lost on a tangent of thinking like what is the limit like how fast can you make a camera lens because you really get you know F 0.1 or 0.2 or something and I found a supplier that makes two foot diameter fresnel lenses with relatively short focal lengths about half of their diameter so if I did that with the same setup or maybe even three stages first a two foot diameter focal or a two foot diameter fresnel lens and then the one foot diameter in a lens and then this Glass lens in the back I have a feeling it would work and to make the thing even faster we're giving up things like you know focal plane planarity and coma and you know all kinds of other aberrations but at this point we really don't care we just need as many photons as possible it needs to be a very fast lens and that's what this is one thing I haven't talked about yet is potentially using artificial light to make these Leaf prints instead of sunlight I did do a little bit of study to check how much light was making it through the 35 millimeter film negatives and it's actually not very much I have a photosynthetically active light meter that measures how much light is actually usable for a plant and as it turns out a 35 millimeter film negative cuts out about half the usable light right there I also tested my piece of acrylic that I put over the top to hold the thing flat and that only removes a few percent so really most of it's getting lost in the film Emulsion as it turns out the transparencies from an inkjet printer are also quite a bit better so if you're struggling with this a 35 millimeter film negatives are one of the more difficult things to get working right away I would start with transparencies from an inkjet printer and I talked about these pretty extensively in my screen print video so anyway getting back to the idea of using artificial light to make these plant prints I'm going to do a separate video on measuring artificial light sources and comparing them to sunlight someone just loaned me a sulfur plasma lamp which is a really unusual microwave powered light source that is great for indoor growing and I'm going to compare that to mercury vapor and led using a spectrometer and go into all that stuff the short answer is that it's pretty difficult to get working to make these plant prints sunlight is amazingly powerful and of course plants have adapted to it over a very long time so if you're in a summer climate definitely start with sunlight it's by far the easiest way if you're in a winter climate you might be forced to use artificial light to make these plant prints and you might require much more intensity than you might think some using lenses are something to focus a huge amount of light down onto the plant is probably going to be necessary here's some last bits of advice if you decide to try this yourself if you're developing a leaf and you think it's not looking good just keep going keep processing it and dry it out as normal sometimes the image doesn't look very good until after the leaf is fully dried and you don't want to you know cheat Yourself by throwing it out Midway also there's lots of different kinds of geraniums so if you're trying this and it's not working very well get a hold of a different plant either a different you know subspecies or you know version of geranium or just a different separate plant of the same exact species may surprise you and how different it is also some types of geranium have like black coloring on the leaf very interestingly this has almost no impact on the image forming properties like that black band disappears entirely when you boil it in alcohol and it appears to be just as sensitive to photosynthesis as the parts of the leaf that don't have that black coloration so you can go right over the top of that with your image mask and when you develop it it's almost like there was no black coloration there at all it just seems to have no effect also keep in mind that throughout this video I've been showing you my best results and I've been doing this pretty much every weekend for the last few months so I've processed you know over 100 leaves easily and I would say my hit rate now is yeah maybe about 20 or 30 percent I'll get something that's worth looking at even with the experience I've gained so be patient with the process it does take a lot of tweaking and you are relying on biology which can be kind of fickle so anyway I hope you give this a try and I'm happy to answer questions in the comments and I hope you found that interesting and I will see you next time bye

Channel: Applied Science

Views: 124,710

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Id: -qETedzsFIE

Length: 21min 41sec (1301 seconds)

Published: Sun Aug 27 2023