Hi from 52°39'6" N 4°50'9" E

[Herman1705]

Hi all, my name is Herman. I live in Heerhugowaard, the Netherlands. I'm an engineer in applied physics (BSc) and work as radiation protection expert in the north west of the Netherlands. A few years ago I started making infrared images with my D7000 (HOYA R72 filter) and later on with my D750 (HOYA R72 and Travor 850nm). This year I got a second hand Sony A500 and had it converted to full spectrum by ACS in the UK. With help of this forum and Ebay I bought an Enna München Lithagon 35mm 1:3.5 and also found good information on filters for UV images. After calculating the transmissions for UV and the IR leak I bought HOYA U340 (2 x 1mm) and Schott BG40 (2mm) filters. The supplier of the BG40 attached a UG11 to it (for free). So I now can compare the U340 and the UG11; there is a lot more green with the UG11. However, I doubt the quality of the UG11 (is it fake or not?), after white balancing I get almost 'normal' coloured VIS images. When you search Flickr for Herman1705 you can find my UV/VIS/IR images.

 

Herman

[nfoto]

Welcome to UVP. I am sure your questions will be answered by our competent members.

 

Have you tried the "standard" UV bandpass filter, the Baader U?

 

PS: Google Maps indeed confirms you live in Heerhugowaard - been to the Netherlands many times but haven't visited that part of the country yet DS

[Andrea B.]

Hello - and welcome to UVP.

 

I'm so happy to hear that you have found our quiet little forum useful in starting your UV journey. :)

 

******

 

About your two filters, the Hoya U-340 and the Schott UG11: both filters dually transmit both UV and IR and thus must be IR-blocked to use successfully for UV photography. Obviously you are aware of this since you have purchased a BG40. :D

 

UV response and thus UV false colours are dependent upon a large number of input variables: illumination, in-camera settings, filter glass, camera sensor, camera software, converter/editor software, time of day, altitude and so on. More false green from one filter stack is not necessarily an indication of it being bad glass.

 

I would suggest that you perform a white balance step in your chosen converter on the same area in the raw U-340 + BG40 file and the UG11 + BG40 file. This will standardize your result. Post them here in a thread and we will take a look and try to help you figure things out. I have this glass myself, but not in the thicknesses you have. However I can run a quick test to ascertain any differences I might see. This might help you.

 

The test would be quick, but getting to this test might take a day or two!!

I have a bit of a backlog of experiments and other chores right now.

 

Also, please use the private PM system to write to me and let me know who was the vendor of your two filters. Then I might be able to offer you an opinion as to the likelihood of the glass being authentic.

Click the envelope icon by your name in the upper right-hand corner, select "compose new" and address the PM to "Andrea B."

 

Note: When posting photos here, we typically add a short summary of the camera, lens and filter info as captions preceding the photo to identify to others what is being seen. This forum software has an "Add to Post" button which permits you to place the attached photo anywhere within your post.

[Andrea B.]

 

Herman, I tried a search of Flickr on Herman1705 and got an error message. Perhaps you can provide a link? Thanks. :D

[Herman1705]

> Herman, I tried a search of Flickr on Herman1705 and got an error message. Perhaps you can provide a link?

 

Please try this:

[Andrea B.]

Yes, that link is good, thank you! You have some nice work there. :)

 

Your UV photos of the big flower bouquets both look within the normal range for your U-340 and UG11 filters. You didn't say what you stacked them with so I'm assuming the BG40. There will always be minor variations in false colours and white balance. You didn't say how you made the white balance for each photo, so I'm unable to analyze the photos any further. And it's always best to look at the raw versions anyway.

 

To best compare the response between the two filters, I would suggest photographing the same subject under each filter and then extracting the raw composites and raw histograms using an app like Raw Digger or Dcraw. That way white balance does not influence the comparison. I'm always happy to run a couple of raw files through my copy of Raw Digger for anyone who does not have it.