UV-IR cut filters - Whats-up-with-it ?

zoolander · 02-21-2013, 11:17 PM

Re - spider picture: Picture taken under a patio in mid afternoon in full shade. At first I thought it was overexposure, so I lowered the exposure compensation until it got too dark, but to no avail.
In the posted picture, at f/10 exposure compensation was at zero, and this was the only photo out of dozens with just a tiny hint of blue.
The spider was light blue, the image is not over exposed, images underexposed didn't reveal the full/true color blue. The blue simply disappeared. Sony A65 does not overexpose, its a very competent camera. Nikon D3000 tended to underexpose (and stop auto focusing, metering and shooting because of RAM lock).

Re - Grasshopper: Picture taken with Sony A65 18-55 (kit lens) on full set of extension tubes, in afternoon sun. Perhaps you are right about you're comments, but I wasn't using a polarizing filter, just a UV filter. I posted this JPEG because I can't find JPEGS from my D3000, only RAW images, and I wasn't about to process hundreds of D3000 RAW's to find a stupid grasshopper with unseen markings.
The main point was this - when using the D3000, you look through the view finder at the grasshopper, on the winglets behind the thorax there is coloration. You take the picture but the coloration is not there. From memory, there was something else going on on the thorax also, but was not captured. The winglets were the most profound disappearance.

I've shot other spiders and caterpillars and wasps etc.etc. But these two were the most obvious disappearance of detail. My human eye see's it, but the camera doesn't see it ...... like some kind of voodoo magic. (Sony A65 uses a OEL display viewfinder- see's what the sensor see's)

I believe it has something to do with infrared light, you do not.

When my filter arrives I'll test it out, and if I'm right, then I'm right. If I'm wrong, then I'm wrong. I'll post a review of the filter on Pentax forums and explain something about it.

As for what I've seen performance wise of these filters, I really like what I see and I intend on using one to compare images with or without the filter.

Ever since I got into DSLR, there's always been something weird going on with it, and my feeling is its infrared getting in.

I can't find the specs on the low pass filters from the different models, where do you find specifications for a K-5 ? (its not in the manual)

**Digitalis** · 02-22-2013, 12:03 AM

Originally posted by zoolander

The spider was light blue, the image is not over exposed, images underexposed didn't reveal the full/true color blue. The blue simply disappeared. Sony A65 does not overexpose, its a very competent camera.

All cameras can be made to over expose. And if you really knew what you were doing you would have used the camera in manual mode, and not have used flash. The reason that image of the spider was over exposed is because you didn't use flash exposure compensation, the second reason why that image is unlikely to have been contaminated by IR is this:

Spectrum for Nikon SB-16 Xenon flash tube - this is pretty representative of all Xenon arc tubes used in modern flash units. Many flash tubes are made of type of glass that filters the flash output to attenuate UV and IR light, but there is still a considerable spike in UV output. Studio flash tubes typically have stronger UV filters on their flash tubes

Xenon flash tubes do produce some IR, but not enough of it to cause problems with colour rendering - camera manufacturers go through a considerable amount of trouble to test the equipment they make and be sure that their products work well together to produce good results.

zoolander · 02-23-2013, 08:32 PM

Like i said, I spent a half hour using various settings: Various apertures; changes to exposure compensation; With flash; without flash; changes to flash compensation. The photo posted is with flash and was the only one that had a hint of blue. Looking at the EXIF data it was at f/16, 1/60th, ISO 100 (not sure whether I stated it before). It shouldn't be that difficult to capture the actual color of the spider. It hasn't taken a half hour to almost capture any spider/bug in the past.

The last word will be your's .........

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
For Sale - Sold: SF1 with Sunpak 344D, Hoya 35 f/2.8 with Tiffen CPL and UV filters.	VoiceOfReason	Sold Items	31	04-20-2013 11:22 AM
Whats up with the Pentax Photo Gallery?	robert	Photographic Technique	17	04-23-2010 03:17 AM
For Sale - Sold: B+W 72mm 486 UV IR cut multicoated	konraDarnok	Sold Items	0	11-02-2009 06:00 AM

02-21-2013, 11:17 PM	#16
zoolander Veteran Member Join Date: Dec 2012 Location: Gold Coast Photos: Albums Posts: 351 Original Poster	Re - spider picture: Picture taken under a patio in mid afternoon in full shade. At first I thought it was overexposure, so I lowered the exposure compensation until it got too dark, but to no avail. In the posted picture, at f/10 exposure compensation was at zero, and this was the only photo out of dozens with just a tiny hint of blue. The spider was light blue, the image is not over exposed, images underexposed didn't reveal the full/true color blue. The blue simply disappeared. Sony A65 does not overexpose, its a very competent camera. Nikon D3000 tended to underexpose (and stop auto focusing, metering and shooting because of RAM lock). Re - Grasshopper: Picture taken with Sony A65 18-55 (kit lens) on full set of extension tubes, in afternoon sun. Perhaps you are right about you're comments, but I wasn't using a polarizing filter, just a UV filter. I posted this JPEG because I can't find JPEGS from my D3000, only RAW images, and I wasn't about to process hundreds of D3000 RAW's to find a stupid grasshopper with unseen markings. The main point was this - when using the D3000, you look through the view finder at the grasshopper, on the winglets behind the thorax there is coloration. You take the picture but the coloration is not there. From memory, there was something else going on on the thorax also, but was not captured. The winglets were the most profound disappearance. I've shot other spiders and caterpillars and wasps etc.etc. But these two were the most obvious disappearance of detail. My human eye see's it, but the camera doesn't see it ...... like some kind of voodoo magic. (Sony A65 uses a OEL display viewfinder- see's what the sensor see's) I believe it has something to do with infrared light, you do not. When my filter arrives I'll test it out, and if I'm right, then I'm right. If I'm wrong, then I'm wrong. I'll post a review of the filter on Pentax forums and explain something about it. As for what I've seen performance wise of these filters, I really like what I see and I intend on using one to compare images with or without the filter. Ever since I got into DSLR, there's always been something weird going on with it, and my feeling is its infrared getting in. I can't find the specs on the low pass filters from the different models, where do you find specifications for a K-5 ? (its not in the manual)

02-22-2013, 12:03 AM	#17
Digitalis Site Supporter Join Date: Mar 2009 Location: Melbourne, Victoria Photos: Gallery Posts: 11,694	Originally posted by zoolander The spider was light blue, the image is not over exposed, images underexposed didn't reveal the full/true color blue. The blue simply disappeared. Sony A65 does not overexpose, its a very competent camera. All cameras can be made to over expose. And if you really knew what you were doing you would have used the camera in manual mode, and not have used flash. The reason that image of the spider was over exposed is because you didn't use flash exposure compensation, the second reason why that image is unlikely to have been contaminated by IR is this: Spectrum for Nikon SB-16 Xenon flash tube - this is pretty representative of all Xenon arc tubes used in modern flash units. Many flash tubes are made of type of glass that filters the flash output to attenuate UV and IR light, but there is still a considerable spike in UV output. Studio flash tubes typically have stronger UV filters on their flash tubes Xenon flash tubes do produce some IR, but not enough of it to cause problems with colour rendering - camera manufacturers go through a considerable amount of trouble to test the equipment they make and be sure that their products work well together to produce good results.

02-23-2013, 08:32 PM	#18
zoolander Veteran Member Join Date: Dec 2012 Location: Gold Coast Photos: Albums Posts: 351 Original Poster	Like i said, I spent a half hour using various settings: Various apertures; changes to exposure compensation; With flash; without flash; changes to flash compensation. The photo posted is with flash and was the only one that had a hint of blue. Looking at the EXIF data it was at f/16, 1/60th, ISO 100 (not sure whether I stated it before). It shouldn't be that difficult to capture the actual color of the spider. It hasn't taken a half hour to almost capture any spider/bug in the past. The last word will be your's .........