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UltravioletPhotography

Pentacon 50mm f/1.8 and speed booster for UV photography?


Avalon

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Recently I decided to buy vintage Pentacon 50mm f/1.8 Multicoated Auto lens because it offered nice image quality and was not expensive for modification. Lens offered much better image quality than my UV modified Jupiter 9 50mm f/2 lens in terms of both visible light and infrared photography at least on APS-C camera. Lens exhibits no infrared hotspot as much as I see so it’s good candidate for IR photography, I will provide below some photo samples both f/1.8 and f/16. But note that images were cropped due to smaller sensor size, I was holding lens with hand and they were not very clean.

 

https://drive.google...FTaF5dnLKX8l4Ns

https://drive.google...tvSieFaXB7PwLc-

 

When tested lens against 365nm ZWB2 3mm filtered UV radiation I noticed bluish white fluorescence probably from optical cement (does multicoating do that?). As opposed modified Jupiter 9 under same conditions looked completely clear. Nevertheless Pentacon lens can be used for UV photography, here is photo made under mentioned UV source of my clear glasses blocking UV using QB21 2mm and ZWB1 2mm. BTW is UV supposed to look reddish with full spectrum camera?

 

https://drive.google...BeSEiR37vLtD7M_

https://drive.google...vZEgBqzNtCKNgyz

https://drive.google...a5nD3Hg8_9TpboS

 

I also consider using this lens with speed booster converting full frame to APS-C image but I’m not sure how it will affect IR and UV image quality. Anybody had experience with them? I’m considering order cheaper M42 to NEX speed booster if it will provide good image quality: https://www.ebay.com...er/273768858094

Later I plan try to recement Pentacon lens although it seems that lens are cemented using not Canada balsam but some kind synthetic resin as there is no visible yellowing so I’m not sure if dimethylformamide will work. Speed booster lens will also be cemented with new cement. I read at least that Norland optical cement can be dissolved using methylene chloride with methanol and ammonia added to aid separation process. Also I prefer to leave multicoating so solvent must not damage it.

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Before you break a lens, I think you need better filters. The ZWB2 and ZWB1 may be ok, depending on whom you got them from. The QB21 is junk. It will not adequately block IR. You will have IR in your photos.

Just look at any of Dmitry's len test using a Qb21, there is a ton of IR coming through.

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I know that, but ZWB1 and QB21 is what I can afford currently. I plan on upgrading later because I may need equipment for professional use. Indeed when photographing under artificial UV source flower have more contrast, blacks are deeper. Still QB21 does it's job as visible and UV spectrum photography filter, infrared leak could be prevented by selecting thicker filter like 3mm. Here I attach some photos flowers, animals and nature in UV (white balanced with false color in Lightroom). Lens seems not be so sharp in UV. Sony a3000 has nice feature for manual focus lens that marks with golden pixels very sharp points on image but with my lens they appear in visible light photography. No matter how well I focus no such markers are visible, can this be due to infrared leak or lens is designed to focus sharply UV rays?

 

https://drive.google.com/open?id=1aLuJ-H580iK1M1bv1UbrsxvAt7EHurL3

 

https://drive.google.com/open?id=1Gl_BN9of08bcLfsLf9hx2ZuaUAgeCQK0

 

https://drive.google.com/open?id=1RynfRm7-fUeojmAMqIfK2jM095JK7S08

 

https://drive.google.com/open?id=1yJickzl0yfrt35I49obaW26prbrt7_eq

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A thicker filter does help mitigate the IR leak, but not entirely. I tried a 5mm stack of U340 and still saw some IR leak! But not much.

We do understand that not everyone can afford the good filters. UV/IR can be an expensive thing! It can take a long time to accumulate all the necessary gear.

 

I do note that there is a wide range of quality in the ZWB and QB filters because there are so many different manufacturers of this glass in China. Some are OK. Others are not. The problem is that there is no way to know in advance what you are getting.

 

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When tested lens against 365nm ZWB2 3mm filtered UV radiation I noticed bluish white fluorescence probably from optical cement (does multicoating do that?

 

My experience is that some optical cement or certain types of glass can fluoresce. I don't think I've seen any fluorescent coatings. Maybe some other members can also contribute here?

 

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A speed booster can affect UV/IR work depending on what glass is used and/or how it is coated. Using one probably will might confine you to the 380-400 nm range.* That is quite sufficient to get a legitimate reflected UV photograph and should not be regarded as deficient. It is just restricted.

Again, if anyone reading can help with this, please weigh in.

 

Added later:

*But our member Dmitry has reminded us in the next post #5 that he measured a speed booster down to 365 nm.

 

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BTW is UV supposed to look reddish with full spectrum camera?

 

The false colour in a UV photo is dependent on your camera settings and your converter settings (and other factors). If you perform a white balance on a raw reflected UV photo, then the red/orange/pink colors will change to grey/blue/yellow. Of course, the white balance step is a matter of choice. You can present a UV photo in whatever false colors are pleasing to you. Typically raw UV photos in the range between 350-400 nm and before white balance have an orange/pink/red/magenta/violet appearance dependent upon the UV-pass filter used.

 

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Hey, there! Please do be careful with such chemicals as methylene chloride.

That is rather dangerous stuff!!! :o

 

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Sony a3000 has nice feature for manual focus lens that marks with golden pixels very sharp points on image but with my lens they appear in visible light photography. No matter how well I focus no such markers are visible, can this be due to infrared leak or lens is designed to focus sharply UV rays.

 

Focus peaking, as it is called, does not always work well in UV. It could be due to lack of sufficient UV light or the angle of the primary light. Sometimes focus peaking is dependent on distance from the subject. And of course, some cameras are better at focus peaking than others. The newest cameras seem to have much better focus peaking. Experiment - move around and reframe closer or further away, change the angle of illumination, change the aperture, use a thinner filter while focusing. Most cameras which offer focus peaking have a setting which lets you increase/decrease the focus peaking strength. Try resetting that.

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Thanks for the reminder, Dmitry! That's a good reach to 365 nm.

 

I am going to edit my comment above.

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