Freezing a water spray

Started 5 months ago | Discussions thread
Sailor Blue
Sailor Blue Forum Pro • Posts: 15,527
Re: Freezing a water spray

Robert Demo wrote:

Ellis Vener wrote:

Robert Demo wrote:

Ellis Vener wrote:

Are you trying to document

1) size of droplets

2) speed of droplets

3) shape of droplets

4) spray pattern

5) density of spray per mm or micromillometer

6) saturation pattern per time period

7) All or some of the above

What angle are you photographing the spray from?

Actually none of these. I am trying to impinge two thin sheets at one another. When they impinge they combine into a mixed sheet. After 5 to 10 milliseconds (depending upon the sheet velocity), the mixed sheet breaks up into droplets. I'm not at all interested in the droplets.

The impingement zone has dimensions of around several centimeters in length, 250 microns in width and 150 microns in depth. I want to get a closeup clear shot at the 250 micron dimension because I suspect that there is something else going on when they impinge that can't be seen with the naked eye. It would be really great if I could attach one of the photos I took with the iPhone. Is that possible?

It sounds like high speed video as well as stills will be useful. But also it sounds like you’ll need a macro lens.

Macro lenses confuse me. As I understand it, they zoom in, but I'm not sure how well they can focus. Also, I get confused with the "macro" setting. I think the macro setting just allows for focusing when the camera is very near to the object. I don't want the camera to get too close because water will be spraying around (the camera will probably be about 12 inches away). The Casio camera provides 1000 fps which is hard to get at a very good price. However, 1000fps isn't really fast enough but is better than real time. Ultimately a Phantom camera at 1,000,000 fps is what will be needed, if I can convince a university to underwrite some research. I guess it's not possible to attach photos.

Thanks for all of your help.

So you are trying to photograph what is happening at the mixing zone of two sheets of fluid.  Images from the side should be possible.  What isn't certain is whether even a macro lens capable of a 1:1 size image of the subject on the camera's sensor (which would blow up to the size of your monitor) would give you enough details.  If not then you are starting to get into taking photos with a camera attached to a microscope.

Many zoom lenses call themselves macro lenses but they aren't. They are simply lenses that can focus from a little closer than from the "normal distance" to the subject so they give you a slightly larger image on the camera's sensor. What is the "normal distance" is up to the manufacturer so lots of marketing and advertising departments simply tack the "macro" name on any lens they want.

A true macro lens is capable of producing a 1:1 image.  The can used close enough to the subject that the image of the subject on the camera's sensor is the same size as the subject itself, or even larger than the subject with a few macro lenses. There may be some true macro zoom lenses but all the true macro lenses I know of are all fixed focal length lenses.

The wider the focal length of the macro lens the closer it must be to the subject for the same image size. Using a longer focal length is what I recommend for most uses since your lens is further from the subject. I wouldn't recommend anything with a shorter focal length, especially if you have liquids spraying around and they can get on the lens.

There are some very good macro lenses in the 85mm to 100mm range.

I recommended the Tamron SP 90MM F/2.8 Di 1:1 Macro lens ($649 new) in a previous post. It was a good budget priced lens for me since I got it secondhand for less than 1/2 the new price.

Nikon has two macro lenses, the $596.95 60mm f/2.8 macro lens and the 85mm f/3.5 macro, which is marked down from $635.00 to $556.95 now. The second would be the lens I would recommend if you decided to buy a Nikon lens.

Sigma makes the 105mm f/2.8 macro lens that sells for $469.00.

With any macro lens accurate focus is extremely important so be sure if you buy a Nikon camera be sure it can do Focus Tuning with any lens you buy.  The alternative is to use the camera's live view LCD instead of the viewfinder, set the LCD image magnification as high as possible while keeping the zone of interest in the image, and manually focus the lens.

I'm sure that other forum members have opinions about these lenses.  If not the do a post asking what is the better choice among these lenses.

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Living and loving it in Pattaya, Thailand. Canon 5DS R & 7D - See the gear list for the rest.

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