StephanN Posted August 29, 2020 Share Posted August 29, 2020 Not sure if this is the right section to post this, and if this is of interest at all? When I walked through the cemetery for this thread https://www.ultravioletphotography.com/content/index.php/topic/4085-cemetary-in-uv-ir/ , I ran across a small fountain and thought I could perform a small test how it looks like when photographed with different exposure times. I used the El-Nikkor 80 mm, at f/5.6, for all of them, with the camera on a tripod, of course. The first photos are just an overview to show the fountain: Next are the four comparison shots (I didn't bring any of my nd-filter, but I doubt that longer exposure times would have resulted in anything special, except smearing out the small leaves): 1.6s, ISO 1600: 3.2s, ISO 800: 6s, ISO 400: 25s, ISO 100: Link to comment
Cadmium Posted August 29, 2020 Share Posted August 29, 2020 Stephan, Oh, those are very nice and pleasing to my eye. Link to comment
Andy Perrin Posted August 29, 2020 Share Posted August 29, 2020 I like the last one best. I would like to see how it would have fared with my water-blackening IR filter. Link to comment
nfoto Posted August 30, 2020 Share Posted August 30, 2020 Eventually given long enough exposure times, water becomes a mist then even trsnsparent so you can "see through" it. An approach I used to photograph underwater topography in rivers. If the water is too deep, one can still evaluate the topography by the riverine surface unevenness. Link to comment
dabateman Posted August 30, 2020 Share Posted August 30, 2020 Eventually given long enough exposure times, water becomes a mist then even trsnsparent so you can "see through" it. An approach I used to photograph underwater topography in rivers. If the water is too deep, one can still evaluate the topography by the riverine surface unevenness. But not with a 980bop filter like Andy found to catch the water absorbing peak.Then it will look thick, like blood. That may or may not be appropriate for a cemetery fountain. Depends on the movies you have been watching. Link to comment
nfoto Posted August 31, 2020 Share Posted August 31, 2020 Still one will have the 'surface' effect. Meaning with a water flow across an uneven bottom of the river, the surface will mirror those bumps too. Link to comment
nfoto Posted August 31, 2020 Share Posted August 31, 2020 Here is an example. First is just a normal exposure of a coruscating water surface of a Norwegian alpine river, Now, do a multiple exposure of 4096 frames (film) or using an extreme ND filter (digital), The uneven bottom topography is clearly reflected in the [time-averaged] water surface. (this approach will work best if water flow is fairly constant during the exposure time, which should be the case in most situations) Link to comment
dabateman Posted August 31, 2020 Share Posted August 31, 2020 Here is an example. Now, do a multiple exposure of 4096 frames (film) or using an extreme ND filter (digital). Birna you shot 4096 frames of film! That 114 rolls to get that shot. That is some serious dedication. 57 rolls if on a Pen-FT half frame camera. Link to comment
Stefano Posted August 31, 2020 Share Posted August 31, 2020 Well, the maximum I did was like 1000+, I think less than 2000, I don't remember the exact number. And they were digital (I never shot film). That's truly impressive. Link to comment
nfoto Posted September 1, 2020 Share Posted September 1, 2020 Birna you shot 4096 frames of film! That 114 rolls to get that shot. That is some serious dedication. 57 rolls if on a Pen-FT half frame camera. A single roll of film -- the key word here is "mutli-exposure" .... That single frame involved having the camera run for hours (!) around 2.5 hrs if memory serves. This despite the shutter speed was 1/8000 sec. One has to have a small interval between frames otherwise vibrations will build up in the camera/tripod system however good the support is. The first occasion I applied this method to ended by the camera literally doing break-dance on its own. Mistakes are the fastest way to learning. Link to comment
StephanN Posted September 1, 2020 Author Share Posted September 1, 2020 A single roll of film -- the key word here is "mutli-exposure" .... That single frame involved having the camera run for hours (!) around 2.5 hrs if memory serves. This despite the shutter speed was 1/8000 sec. One has to have a small interval between frames otherwise vibrations will build up in the camera/tripod system however good the support is. The first occasion I applied this method to ended by the camera literally doing break-dance on its own. Mistakes are the fastest way to learning. So was this IR-film? I've done my share of long-exposures with water, but only VIS so far. I might have the opportunity next week to take a few of a small brook with lots of rocks and some plants, what do you suggest works best, UV, IR, VIS? UV would have the advantage of not needing any ND-filters Link to comment
StephanN Posted September 1, 2020 Author Share Posted September 1, 2020 Stephan, Oh, those are very nice and pleasing to my eye. Thanks. I like the last one best. I would like to see how it would have fared with my water-blackening IR filter. What would you expect with an ordinary IR-filter? I could go back sometime, it's not far off. Link to comment
Andy Perrin Posted September 1, 2020 Share Posted September 1, 2020 Thanks. What would you expect with an ordinary IR-filter? I could go back sometime, it's not far off.If you use a 1000nm long pass filter it will look darker, although not as dark as my bandpass at the exact peak. If you use a 720nm long pass (like R72) it will just look like normal water almost. Link to comment
StephanN Posted September 1, 2020 Author Share Posted September 1, 2020 If you use a 1000nm long pass filter it will look darker, although not as dark as my bandpass at the exact peak. If you use a 720nm long pass (like R72) it will just look like normal water almost. I see, my camera is converted for 700 nm, but I've got 850 and 950 nm filters for that blinding white Wood effect Link to comment
Andy Perrin Posted September 1, 2020 Share Posted September 1, 2020 Try the 950nm. That has a cutoff close to the peak in fact, and your camera's gain falloff may do the rest. Link to comment
Stefano Posted September 1, 2020 Share Posted September 1, 2020 I might add your (future) images in my topic about the water absorption spectrum... I still have to finish the tables... Link to comment
StephanN Posted September 1, 2020 Author Share Posted September 1, 2020 Try the 950nm. That has a cutoff close to the peak in fact, and your camera's gain falloff may do the rest. Thanks, will try Link to comment
StephanN Posted September 1, 2020 Author Share Posted September 1, 2020 I might add your (future) images in my topic about the water absorption spectrum... I still have to finish the tables... Sure, now I have to go back and take those photos Link to comment
dabateman Posted September 1, 2020 Share Posted September 1, 2020 Birna,That makes a lot more sense. I knew I was missing something.Some digital cameras can do that too. Olympus allows for 2 frame overlay. Some Nikon cameras allow for 10 frames. Some film cameras have the shutter wind up seperate from the film advance. So you can do it manually. My instant film camera will work that way. So you can do multiple images on the instax film.I hope it gets mailed off soon. I look forward to playing with it. Stephan, you have been posting some excellent images lately. I really have to escape the full lock down and photograph something. Been too long for me. Link to comment
StephanN Posted September 2, 2020 Author Share Posted September 2, 2020 Stephan, you have been posting some excellent images lately. I really have to escape the full lock down and photograph something. Been too long for me. Thanks :) I'm trying to take as many photos as possible now because schools are starting in 2 weeks time and everybody expects an increase in infections and new containment measures Link to comment
StephanN Posted September 5, 2020 Author Share Posted September 5, 2020 I haven't had time yet to go back to the fountain at the cemetery So, why am I posting again, you may ask The answer is simple: On a short hiking tour I sent my companions ahead and took some time for a couple of comparison shots of a small cascade, just a few meters high but sufficient for the purpose. I made some ordinary shots as well, but for the comparison I used an exposure time of 30s; I just love that smooth water. For UV I used the EL-Nikkor 80, for the others the Canon 24-70. I know that I ought to have used the same lens for all of them, but changing lenses in the woods near water isn't something I'm particularly fond of. Interestingly I cannot see any real difference between 850 and 950 nm, possibly because of everything being in the shade, or because I got cheated with my 950-filter, or ... In any case, I would expect a similar behaviour for the fountain at the cemetery, because that is always in the shade. First visible and one-click convertion (no playing around with the mixture of the different colours) to b/w in Lightroom: Next UV: IR 700 nm: IR 850 nm; IR 950 nm: Link to comment
Andy Perrin Posted September 5, 2020 Share Posted September 5, 2020 Interestingly I cannot see any real difference between 850 and 950 nm, possibly because of everything being in the shade, or because I got cheated with my 950-filter, or ... In any case, I would expect a similar behaviour for the fountain at the cemetery, because that is always in the shade. Here's a stab at some explanation. First of all, 850nm and 950nm both have the bayer filters fully transparent. So any differences will be due to the properties of materials at the respective wavelengths. At 950nm, the water should be darker IN THE ABSENCE OF SCATTERING. When the water is flowing smoothly without much turbulence, there will be very little scattering, but turbulence and bubbles scatter light very well. I think that's why you're seeing a dark surface away from the falls but a lighter color where the water is bubbly/turbulent. Link to comment
StephanN Posted September 5, 2020 Author Share Posted September 5, 2020 Here's a stab at some explanation. First of all, 850nm and 950nm both have the bayer filters fully transparent. So any differences will be due to the properties of materials at the respective wavelengths. At 950nm, the water should be darker IN THE ABSENCE OF SCATTERING. When the water is flowing smoothly without much turbulence, there will be very little scattering, but turbulence and bubbles scatter light very well. I think that's why you're seeing a dark surface away from the falls but a lighter color where the water is bubbly/turbulent. Qute possible. There is a marked difference in the part of the fall with plenty of bubbles between the shots in UV/VIS and the ones in IR. In IR one might be tricked into thinking there's no water at all So you think that in photos with a short enough exposure the difference between 850 and 950 ought to show up? UV, plenty of bubbles, foam, etc.: 950, not so much: Link to comment
Andy Perrin Posted September 5, 2020 Share Posted September 5, 2020 Yeah, the UV/950nm IR difference is pretty much what I would expect here. It's still whiter than the stationary water at the bottom at 950, but the scattering is much higher in the UV obviously for the top photo. A short exposure might make it even more obvious, yes. That wouldn't decrease the bubbles, though. See my results here with the bandpass at the peak. This is probably the best that can be done without going to SWIR:https://www.ultravio...980nm-bandpass/ Those pics (mine) were turbulent but not bubbly for the most part. You would probably have a similar experience with the fountain I'm thinking? Here is what I got with a waterfall:https://www.ultravioletphotography.com/content/index.php/topic/3514-newton-upper-falls-980nm-bp10-filter Link to comment
Stefano Posted September 5, 2020 Share Posted September 5, 2020 Are we talking about Rayleigh scattering? Are the bubbles so small? I'm asking this because it seems to be wavelength-dependent. Link to comment
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