Lighting for macro photography of fern gametophytes

A forum to ask questions, post setups, and generally discuss anything having to do with photomacrography and photomicroscopy.

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Adam Long
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Post by Adam Long »

Lou Jost wrote:Are you really shooting at f/11 as the last picture of the lens suggests?
I've no experience using tube lenses but I would have assumed you would focus it at or near infinity too. Your Olympus 200m looks to be nearer its close focus limit.

jsp
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Post by jsp »

Ooo! That's a good point. I hadn't though of that. I'll try that next. Thanks :-)

jsp
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Post by jsp »

I just checked and it focuses from 2.5m to 30m and then to infinity, and it was set at 30m when I took those photos, so that's not too bad at least. I'll try it at infinity next time.

jsp
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Post by jsp »

I just tried putting the Canon 2x teleconverter on between the camera body and the olympus Zuiko tube lens, and it didn't work for a couple of reason. Firstly the physical design of the tube lens is too narrow at the base when focussed to infinity. If I focus at 15m it fits. Once I set the focus right the lens went on but the camera body was not happy at all and came out with all kinds of weird error messages and couldn't take any shots. Fortunately it was okay when I took the teleconverter off again. It might have been to do with the EOS to olympus converter which also has a chip in it to accommodate the canon electronics.

jsp
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Post by jsp »

I wondered if anyone might know whether speedlites produce light that is somehow hot? It doesn't feel hot to my hand, but my fern gametophytes keep shrivelling up as soon as I start photographing them. I'm wondering if I should switch to LEDs. Thansk!

jsp
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Post by jsp »

I'm practising on a flower of Verbena bonariensis and the narrow stripe of petal tissue in focus really shows how narrow the depth of field is on this lens.

Image

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Chris S.
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Post by Chris S. »

jsp wrote:I wondered if anyone might know whether speedlites produce light that is somehow hot? It doesn't feel hot to my hand, but my fern gametophytes keep shrivelling up as soon as I start photographing them. I'm wondering if I should switch to LEDs. Thansk!
Speedlights can certainly heat up subjects, but I doubt there is anything special about the spectral output of their light that does this. More likely, it's simply the effect of light intensity on your very sensitive subjects. If this is the case, LED's would not likely solve the problem, as you would still need to set them to very a bright intensity, and they would be always on, unless you gated them.

If you wanted to be certain of this, you could try placing an IR blocking filter in front of your speedlight. I suspect that any improvement would be unlikely.

What I think is happening is that intense photographic lighting is causing your gametophytes to process water very rapidly (likely both by transpiration and photosynthesis), outpacing their ability to replace it.

With cut plants, I address this by placing specimens in tiny "vases" of water. Your fern gametophytes are probably a more challenging case. My first thought for attacking your issue is to increase, in any way you can, the moisture available to the plant. Perhaps place its substrate in water? Second thought would be to pause between shots long enough for whatever water is lost during the shot to be replaced before the next one. (Granted that this may backfire, as the longer one works with the plant, the more opportunity it has to move.)

Let us know how you solve this! :D

--Chris S.

jsp
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Post by jsp »

Hi Chris,

Lovely to hear from you! :-)

I hadn't thought about taking the shots more slowly. That's a great idea. I've been concentrating on doing it as fast as possible, but actually I could just do it much slower. Interesting! I'll have a go. :-)

Thanks!

Jen

jsp
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Post by jsp »

I tried again with the fern on a large-ish clod of soil that was very wet from a drop of water that I added in situ. Photos taken with a 1 minute delay in between.

It is like this at the start:

Image

and after 1 hour of shots every one minute it is like this:

Image

It definitely did not enjoy that much.


The part of the fern in contact with the wet soil lasted longer, which is good:

Image

The last good fern photo that I took was taken with natural light only and long exposures but that brings in the other problem of slight movement occurring from all sorts of different places.

Hum.

jsp
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Post by jsp »

I tried moving the flashes 45cm away on either side and turning the ISO up to 5000 (from 400) on the camera and the fern still shrivels up. It's definitely not a fan of the flash.

jsp
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Post by jsp »

I have just tried bouncing the light of three flashes off a reflector sheet above the fern so the flashes are not directed at the fern but it still doesn't look happy about that. The total distance from the fern to the flash would be about 110cm with the bounce.

I also increased the step size to 8 microns to get things going faster, and it's a tiny fern with only a few shots needed. About 60 in the end.

Image

The stack is a bit better at least:

Image

ChrisR
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Post by ChrisR »

Glad it's coming together.
Even if it's curling up a bit...;)

I'd want to know what's causing the curling. Change one thing only, at a time.
Take three identical gametophytes (yeah right... :D )
Supply them all with penty of water, Goldilocks temperature, to avoid shock/rapid diffusion change,
Put one in the dark for an hour
Put one in the light for an hour
Blast one with the amount of flash you want to use, rapidly, then leave it for the rest of the hour in the dark,
Compare ...

OK, that's not going to be precise, but you get my meaning.
Does waving your hands sround the specimens make enough wind for them to move around? Bad. Strong flashes will make frail structures jump about.

Winding the ISO up is a good way to check the effect of the flash if you use use identical lighting positions - going up as high as possible to give the tiniest flash power hitting the subject that you can, the heating effect would, I think, make it insignificant and provide a useful comparison.

If it's just transpiration, the light between the flashes may be significant compared with the light of the flash (try a long exposure to see what it needs to be - you may find eg one pop = a 10 second exposure) so keeping things dim may be worthwile.

Schott etc IR blocking glass is expensive, but there are stick-on films used for windows and greenhouses, eg like this.

Maybe try a cut-flower last-longer solution? Add a tablespoon of sugar and two tablespoons of lemon juice per quart of water.
Chris R

jsp
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Post by jsp »

Hi Chris,

Thanks, yes I see what you mean. I do wonder whether they might just shrivel up without the flash, but when I was an undergrad I used to look at them on open plates under a dissection microscope for ages and they didn't bat an eyelid, so it seems as though the flash must be part of the problem. I wondered if maybe the house was too hot and dry too. I could adjust that.

When I published that last paper I was contacted by a very experienced fern biologist whose books I was reading as an undergrad. He gave me great advice about how to get my spores to grow better, so I have written to ask if has any thoughts on this problem. I know my undergrad supervisor used to photograph ferns in an actual fish tank in order to keep the humidity high, so I think I am not the first person to think about this. :-)

It always puzzles me that the camera can show a beautiful photo of the fern in live view on my laptop screen without special lighting, but I need flashes to take the actual photo. I wonder what that's about? I'm tempted just to take screenshots of the live view and stack those, but I'm sure that's probably a bad idea for some reason that I don't know about.

Thanks!

jsp
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Post by jsp »

I tried doing a Verbena bonariensis flower yesterday and it couldn't handle the flashes either. It's a south african plant and can manage very hot sun indeed.

On that basis, I've moved out into the greenhouse and am trying a fern with only natural light and the glass of the greenhouse to keep the breezes out.

Entertainingly, I can see the fern folding up before my eyes even without the flashes. I do not think that ferns like to be photographed.

jsp
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Post by jsp »

Here is the stack from the slices I got before the fern melted.


Image

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