UVF Mould / Mold on Cream

[Andrew Dayer]

 

Screen grab from a document I'm putting together. Images are looking directly downward onto the cream / mould surface.

 

This is one of those at-the-back-of the-fridge finds. This is a part used pot of cream - strictly crème fraîche, soured cream - that was a few months old.

 

The images were made with in darkness with a vertically mounted Nikon D750 with Nikon 105mm 2.8D micro lens and no filtration. Visible light image lit by a couple of 'macro-flashes'. The UVF image was illumated with a pair of full spectrum modified Vivitar 285HV flashes with 2x ZWB1 2.5mm filters. Still a slight red reflection from them, I think.

 

The visible light blueish, furry, areas clearly fluoresce green with maybe cyan. The white to orange central area  is purple in UVF.

Does anyone have any experience with moulds and their fluoresence and my be suggest an identification. Since this was from a fridge that is used for cheese including occasional blue types I wondered about Penicillium sp of for the blue/green areas. Could that mould also present as white / purple areas?

My main surprise was that the cream itself is, well, cream coloured in UVF. The only illumination was the filtered flash so I suppose it must be a fluorescnce of some sort? At the risk of being sectioned by my wife, I've taken various dairy items into the dark and waved the UV torch at them. They all look more or less like the do in visible light - white to shades of yellow. I didn't find much literature - maybe lactose or casein etc give this effect?

 

 

 

[colinbm]

The fluorescence looks good, but there will be some IR with the ZWB1 on the flash.

[Andrew Dayer]

I did some earlier work with a Hoya UV/IR block filter on the lens. Then I forgot it and didn't see much difference with the unconvered camera.

Do you think the (extra) IR block on the lens is needed after all? I'm really not fully comfortable with my UVF setups so far...

[colinbm]

6 minutes ago, Andrew Dayer said:

I did some earlier work with a Hoya UV/IR block filter on the lens. Then I forgot it and didn't see much difference with the unconvered camera.

Do you think the (extra) IR block on the lens is needed after all? I'm really not fully comfortable with my UVF setups so far...

Yes, The flash has a large amount of IR. The best IR blocker is Schott S8612. The best UV blocker is ZEISS T* UV Filter.
Both will improve the quality of your UVIVF with an unconverted camera & flash.

[Andrew Dayer]

Thanks @colinbm. If I could find a 52mm S8612 or afford (I assume) a Zeiss filter...

I'll go back to developing my UVF technique when I've got past my immediate deadlines. Hopefully, what I've done so far isn't overly and advsersly affected by IR leakage.

[dabateman]

Yes I do see some IR coming through.  It will look different if you filter the IR out, using a visible pass, IR blocking filter on the camera.

The filter choice can be a thick BG type filter or a S8612 or a UV/IR blocking filter.

I saw too much IR going through a BW 486 filter, so wouldn't recommend that.  My favorite is the blocking lens from a Sigma SD15 camera.  But those can't be purchased anymore. 

 

Also sorry, I can't ID that for you.

But it does look good. I had a huge collection of excellent samples in the back of the fridge.  But throw away most of them. I might have some plates now with great grow and should probably through away more stuff. 

[ulf]

I would think the need for IR-blocking depends very much on what kind of unconverted camera that is used.

 

Many stock cameras has a good IR-blocking and might not need a filter.

I have no idea if the Nikon D750 has a good IR-blocking or not.

 

If the UVIVF is in the upper red range a thick BG-type or S8612 will eliminate that red light too.

[Andrea B.]

For rigorous fluorescence work always filter both the light source and the lens/camera as we recommend here: LINK. The internal filtration in stock cameras varies, but it has never had a sharp cutoff on either the UV or the IR end and for some the filtration permits UV or IR leakage. Filtration has improved over the years. Ulf observes below that his Canon & Sony cams have very good internal filters.

 

Amendment made later by Andrea B.

[ulf]

2 hours ago, Andrea B. said:

For rigorous fluorescence work always filter both the light source and the lens/camera as we recommend here: LINK. The internal filtration in stock cameras varies, but it has never had a sharp cutoff on either the UV or the IR end.

I fully agree with most of what you say about rigorous fluorescence work, but not this: "but it has never had a sharp cutoff on either the UV or the IR end."

 

Some camera brands are quite well filtered by the second dichroic filter with a sharp cutoff and good OD.

Both the Canon and Sony bodies I have are good in that respect, while Nikon cameras often are not that well filtered.

 

If you for scientific researches want to measure the fluorescence it is absolutely vital to insulate the excitation light source from the fluorescence bands.

[Andrea B.]

Thank, Ulf. I will amend that to "not every camera has a sharp cutoff......".

 

One factor is that most of us do not really know how well our cameras block UV or IR without some serious testing with really good blocking filters. So I always recommend that both light source and lens be properly filtered when photographing fluorescence. There is a lot of fluorescence photography "out there" for which the creator makes dubious claims about what we are seeing.

 

For some reason, this topic reminds me of the big Leica screw-up when the first Leica digital rangefinder, the M8, first appeared. The IR blocking was so bad that Leica had to make free IR-blocking filters available to use on the lens. That must have cost them a few $$$. 

 

 

[Andrea B.]

I should not forget to say that I really enjoyed Andrew's "sour cream" photos.

Makes me tempted to go buy some dairy stuff for purposeful neglect until the mold forms.  

(Too wasteful maybe? Dunno.)