shooting through water? (was: image stacking and stitching?)

Peter De Smidt · Post by **Peter De Smidt** » Mon Feb 20, 2012 6:45 am

Is that a 30 gallon?

It's a nice size, and the glass will be quite a bit thinner than on bigger tanks.
For the corals on the sand bed, you can always move them a bit closer to the glass for their picture.
Any picture will require some sharpening, either in your RAW processor or in a photo editor such as Photoshop, to look it's best.
Regarding flash, you can always use a filter on the flash head to change the color of it's output.

ChrisR · Post by **ChrisR** » Mon Feb 20, 2012 8:44 am

I don't think I conveyed what I meant - no cameras under water!
A closed "bucket" dipped into the water - probably square sided.
Grey is surface silvered mirror ( eg from Surplus Shed)
Green is a thin camera filter - or again something from SS.
Red distance can be short.
NB fairly long focal length lens.
You could build led lights into the bucket too

Planapo · Post by **Planapo** » Tue Feb 21, 2012 11:05 am

A question related to the problems discussed here:
Let's assume one would like to build some little glass containers/aquaria (inch dimensions) for photography of aquatic critters, is there, apart from Chris' suggestion to use photo filters, any glass material available that will introduce minimal distortion and should hence be the preferred building material?

--Betty

BTW, Though he's not in focus, I think in one of the previous pics I've found Nemo.

Peter De Smidt · Post by **Peter De Smidt** » Tue Feb 21, 2012 11:36 am

Starfire glass is low iron, i.e. water white, glass used in high-end aquariums, but I expect that water white picture framing glass would be best, as it's probably available thinner.

Actually, thin high quality acrylic might be best, but it does scratch easily. If made too thin, though, it might bow, which would be bad.

Drbluethumb · Post by **Drbluethumb** » Tue Feb 21, 2012 2:56 pm

Peter De Smidt wrote:As has been said, before you go to something like stitching, you should maximize the quality of your standard pictures.

1. Clean glass very well.
2. Stop all flow in tank.
3. totally darken room the aquarium is in, since otherwise there will be reflections in the glass.
4. Turn on all of the aquarium lights.
5. Put reflectors on the outside of the tank that'll bounce light back in. Otherwise the lighting can get very contrasty.
6. Shoot with the camera back parallel to the glass.
7. Use a tripod, cable release, mirror lock up...

You may need to adjust your lighting. Super actinic light can be difficult for a camera.

Yes, you can make a small aquarium with thin glass.

Great suggestion's. Thing's I weren't doing were, shooting in the dark, turning the water movement off, using mirror lock up.

Lighting:

is german ati powermodual with fan's to run the ballast/light's cool increasing par output, 6 x t5 high output german bulb's approx 150 watt's, 20 000 kelvin, with german polished steel individual reflector's for each light tube, I think the 150 watt of light is increased by around 2-3 x
that of 150 watt's.

I have the option to run 2 light tubes, 6 light tubes and 4 light tubes.

Aquarium:

is a 29G 24"x24" 12" deep, total height from coral and light is 20"

Drbluethumb · Post by **Drbluethumb** » Tue Feb 21, 2012 4:11 pm

glass is around 1/4" thick, not starfire, didn't measure it, just approx, the coral is placed around 1/4-2" behind the glass, camera is around 1/4-2" outside the glass. no hood just a canon eos t3, 50 mm 1.8 len's and a 12mm extension tube.

wired shutter, tripod

aperture of around 8,shutter a little slower then 1/10th second, iso 100.

ChrisR · Post by **ChrisR** » Tue Feb 21, 2012 4:14 pm

I believe you can get microscope slides, 1 - 1.2mm thick, something about 76mm square, but I can't find where!

Drbluethumb · Post by **Drbluethumb** » Tue Feb 21, 2012 4:21 pm

ChrisR wrote:I don't think I conveyed what I meant - no cameras under water!
A closed "bucket" dipped into the water - probably square sided.
Grey is surface silvered mirror ( eg from Surplus Shed)
Green is a thin camera filter - or again something from SS.
Red distance can be short.
NB fairly long focal length lens.
You could build led lights into the bucket too

I have a 12" deep tank, plus the distance from the mirror, which lens would work?

thanks

Peter De Smidt · Post by **Peter De Smidt** » Tue Feb 21, 2012 4:48 pm

Try upping your iso to get a faster shutter speed.

ChrisR · Post by **ChrisR** » Tue Feb 21, 2012 6:31 pm

which lens would work

Well for 1:1, the distances each side of the lens are the same nominally, at 2 x the focal length of the lens. So for that a 150mm lens would be convenient. ( that's why I suggested it earlier)
Obviously it depends how you arrange the "bucket" in relation to the camera.

For a "thin" lens, the lens to subject distance is given by
FL + FL/M

and the sensor to lens distance by
FL x (1+M)
Where FL = focal length and M = Magnification

So at M=1 you're using quite a lot of tubes/bellows (300mm) if you're using an enlarger lens.
At M = 0.5
you have sensor to lens 225 and lens to subject 450, that's ok I think.
But at M = 2
you have sensor to lens 450 and lens to subject 225, that's not, with this type of lens. You'd want to use a shorter FL and lower the lens into the bucket.

For the higher magnifications, an option would be to use a telephoto lens with a good close-up lens ( dioptre) on the front. Look at Canon, Nikon(old) and Raynox for their two (or more) element ones (see the list in the FAQs.) .
If you use a 3 dioptre CU lens on a telephoto, it'll focus at 1/3 metres from the lens, and closer. ( A 100 - 300 zoom would be a good to try if you happen to have something like that)
The definition you'll get with a CU lens will be better than using an extension tube on a telephoto. It should be good in the centre, but fall off a bit at the edges.
A "process" or enlarger lens will be good across the frame - there are some decent 135/150/180mm ones on ebay under $100 at the moment, Componons, Rodagons, Nikkors, and some less fashionable models.
Watch the nounting though, 39mm is easy, 50mm isn't, afaik.
Again see the faq - Threads we use.

You could try a (say) reversed 28mm lens mounted sideways at the bottom of the bucket the other side of the mirror,
or...
If you got more ambitious, green becomes a microscope coverslip. the lower lens is a microscope infinite objective...
or on reflection, a finite one which does away with the camera lens...

(It's time for bed or I'd sketch this without the camera lens as well...)

rjlittlefield · Post by **rjlittlefield** » Tue Feb 21, 2012 7:26 pm

ChrisR wrote:I believe you can get microscope slides, 1 - 1.2mm thick, something about 76mm square, but I can't find where!

3 years ago I bought a box from The Microscope Depot (http://microscope-depot.com). However, they have now disappeared from the website, and when I emailed the company today to ask about them, I received the following reply:

Thanks for your inquiry. We stopped offering these slides a couple years ago due to a lack of sales. At this point our largest slide is a 2x3 found here:
http://www.microscope-depot.com/accesso ... cy=s-17076

I'm afraid I don't know where else you could get them as we were having them made special for us.

Sorry for the bad news...

--Rik

Charles Krebs · Post by **Charles Krebs** » Wed Feb 22, 2012 12:46 am

2x3" slides are pretty common. Larger are also available...researchers mount some pretty large sections. For example:

http://brainresearchlab.com/online-cata ... nd-larger/

http://www.tedpella.com/histo_html/slid ... hor-slides

Planapo · Post by **Planapo** » Wed Feb 22, 2012 3:47 pm

Picture framing glass and large slides, thanks for the good ideas, guys!

If somebody knows where such large slides can be purchased in Europe in moderate quantities and not waggonload lots, I'd be thankful for a pointer.

--Betty

ChrisR · Post by **ChrisR** » Wed Feb 22, 2012 5:30 pm

A thought - one can still buy glass slide mounts for 120 size film.
You wouldn't want the "antinewton" ones though, unless that 's a coating which might come off in something like paint stripper.

(similarly you wouldn't want antireflection picture glass, it's rough!).

rjlittlefield · Post by **rjlittlefield** » Wed Feb 22, 2012 8:34 pm

Well, I've been chipping away at the aberrations issue.

It turns out that for subjects the size of a pingpong ball, the particular aberration I noted earlier is so small as to be irrelevant. (BTW I've corrected a math error in one of my postings about that.)

However, there's another aberration that can easily creep in and remains important. It's the one that happens when you're not perpendicular to the glass.

Here's an example. These are actual pixels from a Canon T1i shooting through 2 inches of water at 1:1 and nominal f/8 (effective f/16).

Not only is this aberration pretty painful, but it doesn't go away as you stop down. Here's the 10 degrees case, stopped from wide open to effective f/32.

This same aberration apparently kicks in away from center if you shoot with a wideangle lens. I tried Live View at 1:1 through 2 inches of water using an EL Nikkor 50mm, and it got noticeably soft on the edges. In contrast my Canon 100mm f/2.8L IS USM at 1:1 with its entrance pupil almost 300 mm back holds up well across the whole field.

Recommendation: use a long lens and be sure you're perpendicular to the glass.

--Rik