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High ISO sunscreen shot

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#1 JMC

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Posted 06 October 2018 - 21:25

This was in response to a question I recently received about sunscreen imaging. The question was about choice of equipment for visualising sunscreen spreading on skin, without having access to a dedicated UV lens. After initially suggesting a monochrome conversion as the way to go (to try and get as much sensitivity as possible), I thought about whether just very high ISO would be fine and still give usable images to look at spreading and coverage.

To try and stress the system, I did a sunscreen photo using a UV modified Nikon D810 (camera modified by ACS in the UK with one of their proprietary filters), a Nikon 50mm f1.2 lens (nice thick glass and lots of lovely glues and coatings), on an overcast day with no direct sunlight, handheld. My lovely wife was the ever willing model (thank you dear), applying sunscreen to half her face.

This was shot at ISO H0.3 (which I think is 16000 on the d810), 1/30s, f8. Saved as a JPEG in the camera using a whitebalance based on a PTFE tile. Only processing was auto contrast in Photoshop. Quite impressed with the cameras ability to control the noise.

Attached Image: DSC_0505 50mm f8 iso0pt3 small.jpg

Edited by JMC, 06 October 2018 - 21:28.


#2 bobfriedman

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Posted 06 October 2018 - 21:34

yep.. took a shot at the sunflowers of a woman with a V in her forehead which turns out was the way she rubs in her sunblock with both hands facing up.

#3 dabateman

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Posted 07 October 2018 - 02:30

I have found that the brand of sunscreen we buy is reflective, rather than absorbance type. So that can be an issue if your expecting a black face but see pasty reflections.
Interesting to use the Nikon 50mm f1.2, I ruled out mine a long time ago as not being good for uv. But maybe with the 390bp25 it would be ok. It would also let me test vignetting, as I haven't seen that yet with small filters, but the max aperture and front glass on most uv capable lenses is quite small.

#4 JMC

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Posted 07 October 2018 - 09:05

David, this sunscreen had only organic filters in it, which are absorbance filters (hence they look black). Some sunscreens have inorganic particles in them, such as Titanium dioxide, and depending on the particle size (and wavelength of light) they can reflect or absorb UV so can look white under UV. The whiteness of the film on my image is due to reflection from the surface of the product film on the skin. As it is oily, it'll form a smooth surface prone to specular reflection of the UV, irrespective of the SPF ingredients it contains. I chose the 50mm f1.2 as a real stress test with an inappropriate lens. I guess it is pretty much all 380-390nm, but have not tested that to be certain.