Starting the UV journey

[LookCloser]

Hi all,

 

I'm starting the UV journey again now that I have my full-spectrum camera running.

 

I have taken my first shots and I have to say I'm reasonably pleased with them. However, I'd like some feedback on any technical issues that your collective experience can detect in the images. Things like signs of IR leaks, etc.

 

Body: Olympus E-M5Mk1, full spectrum converted (Kolari full spec glass).

Lens: Enna Munchen 35mm f3.5 Lithagon on a macro focusing helicoid.

Subject: Some kind of Asteraceae weed that I expected to show some predictable UV signature. ID welcome.

 

Light was ambient midday sun.

White balances may be a little out, but I'm working on getting an appropriate calibration substrate.

In terms of macro photography there is a lot to be improved on, which I am confident I can deal with over time. It was a very windy day which made longer exposures and smaller apertures unusable.

My primary interest in this tryptich is troubleshooting the out-of-visible imaging aspects of the images.

 

I do feel that there is some leaks going on with the "visible" image because the UV signature is discernable in that image whereas I couldn't really see it in-person.

I will take an image with a stock (unconverted camera next time for comparison as well).

 

All comments and constructive criticism welcome.

Mat

 

 

Series of three images for comparison:

 

UV (Kolari UV bandpass)

 

IR (Kolari 720nm IR filter)

 

Visible (Kolari hot mirror replacement)

[LookCloser]

Edited

[colinbm]

Hey you are on your way, colours look right, perhaps a smaller aperture & more practice on the focus & a tripod will be handy.

[LookCloser]

Hey you are on your way, colours look right, perhaps a smaller aperture & more practice on the focus & a tripod will be handy.

 

Thanks Colin,

The conditions were against me today I'm afraid. The wind was quite strong and I compromised as far as I was willing to with iso and aperture for a faster shutter speed. This was on my macro beanbag, so the shake was purely due to the wind.

 

I have a new toy and couldn't wait to get out there to try it

[Andy Perrin]

Oh this is quite good. The visible may have some UV leakage? Or can you see that bullseye flower pattern with your eyes?

 

Interesting that your Kolari UV pass seems to be functioning properly. People have had problems with that filter sometimes.

[LookCloser]

Oh this is quite good. The visible may have some UV leakage? Or can you see that bullseye flower pattern with your eyes?

 

Interesting that your Kolari UV pass seems to be functioning properly. People have had problems with that filter sometimes.

 

Thanks Andy,

I had read that there have been some Kolari UV bandpass that leak IR, that's one of the things I wanted feedback on. To see if anyone could identify indications of IR leak in the UV image.

 

I was surprised to see the bullseye pattern in the visible spectrum image that I didn't really notice in-person. That would indicate that the hot mirror replacement filter isn't filtering out all of the UV. Perhaps I'll try stacking a UV cut. I think I have one here somewhere.

[ulf]

I had read that there have been some Kolari UV bandpass that leak IR, that's one of the things I wanted feedback on. To see if anyone could identify indications of IR leak in the UV image.

I think that the reasonably good UV-transmission of your lens together with a good UV/IR-ratio of the light saved you here.

 

I suspect that the Kolari UV bandpass filter design is a borderline design that sometimes fail when they get filter glass-materials with slightly less optimal transmission.

[LookCloser]

Thanks UlfW,

That makes sense. I will continue to experiment and will try other lighting conditions to see in which situations it will work well.

[LookCloser]

Here's another question.

For this image I used all of the same gear except I swapped out the lens to use the Weltblick 55mm, another UV capable lens according to the sticky.

 

 

While it shows up the UV signature nicely, there is some significant yellow colour fringing around the yellow flowers.

Is this an issue related to shooting in UV or is there an issue with my lens?

 

[dabateman]

The last image just looks out of focus to me. Like you're just too front focused and the flower is starting to blur out.

 

Not all "good for UV" are actually good lenses though. My 50mm f2.8 Steinheil München lens was soft as butter.

[Andy Perrin]

Yeah, again people tend to obsess about the bandpass around here while ignoring other aspects of lens quality. You do need adequate bandpass but sharpness matters too. I found that the famous Kuri has a wonderful bandpass but is only adequately sharp and inferior to my Noflexar in sharpness. Of the two, I will choose the Noflexar most of the time still (unless I need the bandpass for something special).

[LookCloser]

Thanks Da Bateman and Andy. Your points are well taken. It's easy to get taken in with bandpass aspects and forget that lens quality needs to be considered. This is especially the case as I am using vintage glass where quality varies considerably even between copies of the same lens.

[Andrea B.]

Question on the Weltblick lens --- what aperture and exposure time and ISO.

Like this: f/n for k seconds at ISO-mmm.

Knowing that helps us to help you analyze your photos.

 

Some of those old lenses are very artistic in the sense that they have some "swirl and glow".

But I was thinking there might be some veiling flare in that Weltblick photo.

If so, then the glow might go away if you stopped down further.

[Andrea B.]

I was surprised to see the bullseye pattern in the visible spectrum image that I didn't really notice in-person. That would indicate that the hot mirror replacement filter isn't filtering out all of the UV.

 

Not necessarily so! Many flowers show a slightly different color over the areas where there is an underlying UV absorptive pigment. If you can see it with your own eyes, then it will show up in a Visible photo. Look at the flowers at different angles. I'll note that it is not always easy to see that slight color change with you own eyes.

 

Here is a link to a classic example: the Buttercup. This flower has a very obvious change over the UV absorptive areas. It is easily seen with the "naked eye". Rudbeckias sometimes show this trait. And even the common dandelion sometimes looks a slightly different color in its center where the UV dark will be.

https://www.ultravio...tall-buttercup/

 

Note that in the Buttercup examples, the predictive color change only occurs in the first example. Later example don't show it or show it only slightly.