Jump to content

UV / IR Filter- How to test it?


Guest BigSplash

Recommended Posts

Advertisement (gone after registration)

Surely, there will be enough near-infrared to show in a picture taken with an M8?

Sure, even many compact digicams would show the effect. I’ve just added a paragraph explaining that aspect. But the thing as that if you turn off your soldering iron for example, then once its tip stops glowing red, it will stop glowing in the near infrared range shortly thereafter, so it will usually be missed.

Edited by mjh
Link to post
Share on other sites

Sure, even many compact digicams would show the effect. I’ve just added a paragraph explaining that aspect. But the thing as that if you turn off your soldering iron for example, then once its tip stops glowing red, it will stop glowing in the near infrared range shortly thereafter, so it will usually be missed.

 

Yes, quite.

 

My son uses his digicam to see if the remote control for the tv and similar devices is working, i.e. emitting IR.

Link to post
Share on other sites

I have seen a photo on this Forum of a temp. controlled Weller soldering iron "glowing white" (which is ridiculous of course), but I could not achieve this when I tried it with the same soldering iron!
I was responsible for the soldering iron demo, if I recall correctly it required long exposure times (i.e. at night in kitchen with some stray light). Maybe 2s exposure time. T= 450°C should be sufficient.
Link to post
Share on other sites

If you look at an IR filter off-angle, you will se a red reflection. They used to be called "Hot Mirror" filters as they reflected IR.

 

Chlorophyll in leaves is a good IR reflector, you can count on it.

 

Without Filter, on my M8:

picture.php?albumid=222&pictureid=2277

 

With 49mm IR cut Heliopan Filter, cost $5 used, same lens, on the M8.

 

picture.php?albumid=222&pictureid=2276

 

Black Synthetics: you never know which are IR reflectors until you take an image of them with a camera sensitive to Visible and IR.

 

picture.php?albumid=202&pictureid=1942

 

Above is with my Visible+Infrared Nikon Coolpix 950 of a case that is all-black in the visible only image. I took the IR absorbing glass out of the camera.

Edited by brianv
Link to post
Share on other sites

Filters technically decreases sharpness a little. But we're not talking about pixelpeeping over here, so I'd say no, in real life circumstances they don't have a negative effect. Unless the filter is a bad one, or with fungus, or cracked, etc. If your filter is in good shape, I'd expect a positive benefit.

 

As for UV/IR filters, since the M8 has a very thin of IR blocking filter, then yes, it's a necessity (to me). Some people don't mind, most do. So I'd stick a filter on my lenses.

 

Another downside, if your filter is too thick, it may cause certain vignettes on wide angle lenses. These don't usually happen on normal or tele lenses, but I personally don't mind the vignettes at all, unless it produces a solid black block (which is almost impossible to do unless you stack like 4 -5 filters on a wide angle haha)...

 

To test the UV/IR filter is to try taking picture of a black shirt/jumper on a sunny day. If it turns to magenta, then it's not working. The physical side, the filter coating itself is pinkish/red, and is very very obvious, it glints like that all the time.

Link to post
Share on other sites

Guest BigSplash

Advertisement (gone after registration)

I have now managed to get a black fabric and have achieved images that yield BLACK (with the UV IR filter on) and MAGENTA (No filter) in sunlight. I have also managed to achieve with vegetation a slightly more vivid green (leaves)and yellow (mimosa bush) with the filter on! So success the filter seems to be doing its job.

 

That said it seems to me that the level of difference is slight and seems to be requiring exposure and white balance to be accurate followed by some post processing in Lightroom to really see a big difference.

 

The Marumi Filter (made in Japan) seems to be of excellent glass quality and I bought it from "PopTopShop" on eBay in Hong Kong.

 

I agree with the comment made above that the filter ring is a "little rough" compared to the Leica polished finish, while B&W and Hoya is somewhere in between. The actual glass used on all of theses filters looks very similar (pinkish red when viewed at an angle). When viewed by eye, it seems to me that it could all come from the same place.

 

Since the filter works by interference rather than by absorprtion within the bulk of the glass (ie a colour dye) it suggests to me that this is a piece of glass manufactured or machined to a very high level of accuracy, and one would expect them to look identical. OK I know that to prove this I need access to some specialist test gear.

 

If the B&W or Leica filters were ex stock which they are not and if Leica made a 58mm which they do not it would be interesting to compare prices. I note that the 60mm Leica filter costs £110 (Ffordes), 58mm B&W (Ffordes) at £80 or 95$ plus taxes and duty(BH in USA)...This compares to the Marumi item 35€uros including shipping. about 25% of the Leica price!

 

I also am trying to understand if there is any difference technically between the above filters and what is the specification of the Leica filter ....is it the same as Type 486 from B&W? . The specification of the Marumi according to the supplied plot (see below) suggests a sharp cut off at 680 to 700 nM wavelenth, and below 400nM.

 

I have seen various even cheaper (less than £10) UV IR filters offered on eBay from China. One supplier is offering various UV IR filters with a choice of cutoff values, which seems odd. Presumably the M8 sensor does not want to see anything above 700nM? Does anyone have any feedback on this. ?

 

 

I am interested as I am now looking for a 41mm UVIR filter (for 65m Elmar on Visoflex) that Leica does not have and given my successful experience with the Marumi I cannot see the point of paying high prices for Hoya, B&W etc. Trouble is Marumi do not seem to have a 41mm either.

 

Frankly I am interested in some neutral density filters and eBay is where I shall go first given the above experience.

Welcome, dear visitor! As registered member you'd see an image here…

Simply register for free here – We are always happy to welcome new members!

Edited by BigSplash
No attachment
Link to post
Share on other sites

... Presumably the M8 sensor does not want to see anything above 700nM? Does anyone have any feedback on this. ? ...[/font][/color]

Correct. The vast proportion of humans are unable to see wavelengths above about 700 nm (typically regarded as the top of the visible spectrum) so there's no reason for the M8's or other cameras' sensors to be exposed to this radiant energy in case it produces effects noted above.

 

Pete.

Link to post
Share on other sites

Try shooting some stereo speaker grill covers.

 

I have UV/IR filters, but don't use them in most cases. I find things are sharper and with less flare without them.

 

YMMV, also depends on the lens you use. Some lens filter UV light, some don't. I have a UV flashlight for testing this.

 

Most of the pro- "Use them all the time" remarks are from folks who don't understand that there a) is an IR filter on the sensor, just a bit weak for some IR reflections, not all, and B) that the cutoff of these filters is not where the IR focus shift would occur, in other words, when not using UV/IR cut filters, you don't have a full IR camera, only a camera with a weak IR filter relative to some other cameras and the M9.

Edited by ampguy
Link to post
Share on other sites

Perhaps, but they all vary, and some folks use non-Leica lenses on M8s.

 

I have a '54 coll. cron that passes 360nm clearly, for example.

 

All Leica lenses since 1950 filter UV light, with the exception of the Summarit 50/1.5 and to some extent the Tele-Elmar 90/2.8
Link to post
Share on other sites

Guest BigSplash

I have found the various posts fascinating and informative...thanks. I have come to the following conclusions:

  1. The subject matter, exposure, and light source seems to play a huge part in determining if there is any benefit with a UV/IR filter. If the item is synthetic black material (goes cyan without filter) or vegetation ( not as sharp and vivid without filter) then there is an advantage...albeit offset by:

    1. Possible need to fix profiles if not using Leica filter as the M8 firmware is apparently matched to Leica Filter and not those of B&W or Japanese. However the difference seems to me at least to be super slight.
    2. Potential for more flare, and some reduction of sharpness.

[*]I have always preferred to have a filter on all of my lenses to protect the front lens surface from accidental damage....I have now changed all of my lenses over from a UV, to a UV/IR.

  1. I accept that Leica lenses already have a cut off below about 400nM (the UV range).....but adding the filter surely can only improve the filtration, and does provide the accidental damage protection.

[*]The M8 has some IR cutoff ( above 700nM to 10,000,000nM) that covers near IR, Thermal IR, and Far IR but the attenuation is weaker than M9, which seems also less than adequate at times...so why not accept this and ALWAYS use an external UV/IR filter?

[*]I have now UV/IR filters from Leica, B&W / Schneider / Marumi and Hoya ..optically they all seem equvalent. The finish of the Leica ring is better and the others are the same slightly lower quality.

[*]If there is an issue then IMHO it is all to do with flare ...I have seen this when shooting into the sun, and with a lenshood on. However I really wonder if this is solely due to the filter rather than due to contributions from the lens itself. I have seen this exclusively with wide angle lenses (The old 21mm super angulon seems to be very susceptible and the 1st Generation MATE at 24mm ) It is annoying and I wonder if people have experience with / without filters fitted.

Link to post
Share on other sites

The subject matter, exposure, and light source seems to play a huge part in determining if there is any benefit with a UV/IR filter. If the item is synthetic black material (goes cyan without filter) or vegetation ( not as sharp and vivid without filter) then there is an advantage

There is really no telling in advance whether some subject matter will create problems. There’s nothing special about black fabrics, for example; every color will shift if there is no filter stopping IR contamination. It is just that with black textiles you know that any kind of color you see in the image must be wrong whereas a shift from one color towards another might go unnoticed if you don’t know about the original color or don’t remember. Another critical area is skin tones and these are difficult to get right without adversely influencing other colors.

 

So while one might argue that one should use those UV/IR cut filters only when necessary, in practice it is usually too much hassle trying to predict whether there will be problems. It is simpler to leave the filter on by default and only take it off for shots with light sources within the field of view.

  • Like 1
Link to post
Share on other sites

... then there is an advantage...albeit offset by:
  1. ... some reduction of sharpness.

...

No, as Jaap mentioned above, (since the lens will focus IR image at a different distance from the visible light image), the IR filter will eliminate the unsharp IR image that's overlayed on the sharp visible light image and overall image sharpness should be improved.

 

Pete.

  • Like 1
Link to post
Share on other sites

Guest BigSplash
Black synthetic fibres show magenta without a filter, not cyan.

 

You are right of course .....I have some great magenta images to prove it.

Link to post
Share on other sites

  • 7 years later...

Another issue with a cheaper filter is it may reduce light transmission, e.g. I tried a cheap filter and it increased the required exposure time compared to the B&W which had no negative effect on required shutter speed/aperture.

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...