Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
03-21-2014, 07:52 AM   #1
Site Supporter




Join Date: Apr 2011
Location: Oklahoma
Posts: 309
IR with K3

I know the K3 does not have an AA filter. Does that mean you can shoot IR with the appropriate screw on filter?

03-21-2014, 08:06 AM   #2
Loyal Site Supporter
blackcloudbrew's Avatar

Join Date: Mar 2009
Location: Cotati, California USA
Photos: Gallery | Albums
Posts: 3,782
Good question. I'm interested in the answer myself. One point is that AA filter or not, you can always put an IR filter on a DSLR and get IR images, it just takes a long exposure to get it, and then there is focusing issues etc. That's why IR converted cameras are more desirable. They are IR focus corrected and function like a normal camera.
03-21-2014, 08:11 AM   #3
Pentaxian
awaldram's Avatar

Join Date: May 2008
Location: Hampshire
Photos: Gallery
Posts: 720
QuoteOriginally posted by miltona580 Quote
I know the K3 does not have an AA filter. Does that mean you can shoot IR with the appropriate screw on filter?
AA filter != IR Cut Filter

the K3 still has an IR cut filter
03-21-2014, 08:51 AM   #4
Loyal Site Supporter
AquaDome's Avatar

Join Date: Jan 2014
Location: New Carlisle, IN
Photos: Gallery | Albums
Posts: 1,397
QuoteOriginally posted by awaldram Quote
AA filter != IR Cut Filter

the K3 still has an IR cut filter
To get IR photos with the K-3, you need to block visible light while only allowing IR wavelengths to pass. This can be done by adding IR filters to your lens.
The IR filter covering the sensor will block much of this IR radiation. Thus, a long exposure is necessary to gather enough IR illumination after visible light has been excluded.

---------- Post added 03-21-14 at 09:27 AM ----------

QuoteOriginally posted by blackcloudbrew Quote
Good question. I'm interested in the answer myself. One point is that AA filter or not, you can always put an IR filter on a DSLR and get IR images, it just takes a long exposure to get it, and then there is focusing issues etc. That's why IR converted cameras are more desirable. They are IR focus corrected and function like a normal camera.
IR converted and "full-spectrum" converted cameras are a different kind of beast from "normal" cameras.
Long exposures are still the norm, though not necessarily as long as an unaltered camera with a filter, so its mostly for landscapes.
Also, though I have not experienced any focusing issues, infinity focus is what I mostly use for landscapes.

IR converted cameras have an IR spectrum high-pass filter over the sensor. This allows IR light above the filter's rated wavelength to pass through the filter while blocking visible light. The result is a camera that takes dark pictures within a limited color spectrum. Focusing through the viewfinder is normal. Shorter wavelengths (650nm, nearer to visible light) are red. Longer wavelengths (900nm) appear purple to blue. You pick the filter at conversion time and can't change it. Color adjustment in post processing is more creative than corrective with these images. Auto-focus would work if the filter's thickness was corrected for the difference in wavelengths. Light metering is all over the place. If you know you only want to shoot in a certain spectrum, this is the way to go. Exposures are not as long as if you were using a regular camera with an IR filter, but you now have a dark filter over your sensor. Think of it as having a permanent ND6 filter on the sensor.

A "full-spectrum" camera has had its IR filter removed from the sensor and replaced with clear glass. Images without any added filter appear monochrome-pink. The sensor is really "hot", like ISO1600 when you set it to 100. Focusing happens first, before IR filters are added to the lens. This allows interchangeability of filters across the spectrum. IR-Cut "hot-mirror" filters can be added to the front of the lens to bring the camera back to the normal world. These are the same as the filter that was removed from the sensor, but they aren't as strong, so you would need two. Auto-focus works. Light metering is all over the place. Adding more than two filters to the end of the lens causes vignetting. The "hot-mirror" filters to correct back from the "full-spectrum" conversion cost as much as converting the camera in the first place. The additional IR filters range from $25 to $100 each.

05-26-2014, 12:12 PM   #5
New Member




Join Date: May 2014
Posts: 8
Hi
Can You just confirm in few simple words
Do i can take ir pictures with for example hoya 720 ir filter, without any modification of camera?

thanks
05-26-2014, 02:25 PM   #6
Veteran Member




Join Date: Nov 2010
Location: Edmonton, Alberta
Posts: 800
QuoteOriginally posted by wojtas29 Quote
Hi
Can You just confirm in few simple words
Do i can take ir pictures with for example hoya 720 ir filter, without any modification of camera?

thanks
Yes, you can.


I have the same filter in 49mm. Love it.
05-27-2014, 12:58 PM   #7
New Member




Join Date: May 2014
Posts: 8
Thanks for reply


Can You tell me please how You focusing?
First focus and then apply filter or maybe is there some easier way?


Sorry for stupid question it will be my first time with ir photo
05-27-2014, 09:46 PM   #8
Veteran Member




Join Date: Nov 2010
Location: Edmonton, Alberta
Posts: 800
Yes, I focus first, then put on the filter. That's the only way that works for me.

05-27-2014, 09:55 PM   #9
Veteran Member
OregonJim's Avatar

Join Date: Mar 2009
Location: Willamette Valley, Oregon
Posts: 1,329
QuoteOriginally posted by calculator01 Quote
Yes, I focus first, then put on the filter. That's the only way that works for me.
If you focus without the filter (visible spectrum), the focus point will shift as soon as you add the filter (IR spectrum).

IR focusing is generally done by measuring distance to subject or, if the lens has an IR index, shifting focus to that.
05-27-2014, 10:07 PM   #10
Site Supporter




Join Date: Jul 2009
Location: Los Angeles, CA USA
Photos: Gallery | Albums
Posts: 621
Two thing to keep in mind when you focus.

1) after focus (with the filter off) is achieved, back off on the focus a little bit (then replace the filter). IR will focus in a different manner than visible light. Look at an old manual focus lens and examine the focus index mark and the DOF scale. You will notice a red line/dot/"R" where IR focus index mark is. Take a look, you will understand.

2) do not stop down smaller than f8. IR diffraction is more pronounced at wider f stops than visible. I try not to go narrower than f5.6. You cannot cheat the focus offset by increasing DOF.

---------- Post added 05-27-14 at 10:09 PM ----------

QuoteOriginally posted by OregonJim Quote
If you focus without the filter (visible spectrum), the focus point will shift as soon as you add the filter (IR spectrum).

IR focusing is generally done by measuring distance to subject or, if the lens has an IR index, shifting focus to that.
Sorry for the being redundant. You posted while I was writing.

---------- Post added 05-27-14 at 10:19 PM ----------

Look at the red dot and "R" near the 4 on the DOF scale. That is the IR focus index mark. If using this lens, you would focus normally then rotate the focused distance to that mark.


Last edited by lmd91343; 05-27-2014 at 10:22 PM. Reason: Added "than visible" for point 2)
05-28-2014, 01:22 AM   #11
Pentaxian
Tjompen1968's Avatar

Join Date: May 2012
Location: Norrköping, Sweden
Photos: Gallery | Albums
Posts: 1,287
I turn on Live View and focus.
05-28-2014, 09:06 AM   #12
Site Supporter




Join Date: Jul 2009
Location: Los Angeles, CA USA
Photos: Gallery | Albums
Posts: 621
QuoteOriginally posted by Tjompen1968 Quote
I turn on Live View and focus.
That's impressive. (No sarcasm intended). The LV of the k3 is impressive. Unless I am in the brightest direct sunlight, on my k5 I can only get clouds and some trees against the sky. Even then the image is too dark to focus. In open shade, shadows, and hazy sunlight, LV is useless. I get mostly flashing yellow with a very narrow histogram bunched up on the left margin. My k20 LV is useless. I used an f1.4 lens. I think my filter is a Hoya72. I bought it years ago over eBay. It might be counterfeit, but it produces good images.

Is the display/sensor of the k3 that much better than the k5 or are we using different filters?

P.S. I have only captured IR with my converted k10 for many years. I found it took far too long to take a single good IR photo on an unconverted camera. My wife's patience was the limiting factor. Tripods and guesstimate focusing were required before taking bracketed exposures. Much chimping was involved. It took minutes for a technically (exposure & focus) good photo. That does not include composition prep time!

P.P.S. I found that focusing was easier with my rangefinder film cameras. Just line up the image in the VF, back off to the IR mark, then fire away. Voila, perfect focus!
05-28-2014, 09:51 AM   #13
Pentaxian
Tjompen1968's Avatar

Join Date: May 2012
Location: Norrköping, Sweden
Photos: Gallery | Albums
Posts: 1,287
I use a 720 filter. I also used LV on the K-5, do not remember if K-5 was any different.
05-30-2014, 06:02 AM   #14
New Member




Join Date: May 2014
Posts: 8
I catch today few minutes of sun and made my first try. Just sample

raw files here

I tried set white balance on red grass, and any others settings in camera raw but, basically it still look like shiet.
If possible just look at this pictures and give me some clue please

many thanks

Last edited by wojtas29; 05-30-2014 at 06:25 AM.
05-30-2014, 09:53 AM   #15
Pentaxian
Tjompen1968's Avatar

Join Date: May 2012
Location: Norrköping, Sweden
Photos: Gallery | Albums
Posts: 1,287
You are somewhat overexposed but it looks quite right to me.

Just check this one out;

Basic Infrared Photoshop Techniques Tutorial & IR Instructions
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
camera, cameras, distance, dof, dslr, filter, filters, focus, index, ir, k-3, k3, lens, light, look, mark, pentax k-3, sensor, spectrum
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Abstract IR Trial with K-01 VoiceOfReason Post Your Photos! 4 05-11-2013 08:43 PM
CIF with Kr and IR remote localfocal Troubleshooting and Beginner Help 4 10-18-2012 05:56 AM
Bracketing with IR remote K-30 LoPing Troubleshooting and Beginner Help 5 07-18-2012 10:06 AM
Black & White IR photos with unmodified *istD Swift1 Post Your Photos! 19 05-31-2012 12:14 PM
Converting to IR with PP? slackercruster Film Processing, Scanning, and Darkroom 8 04-01-2012 01:37 PM



All times are GMT -7. The time now is 03:07 PM. | See also: NikonForums.com, part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top