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02-10-2009, 12:33 AM - 1 Like   #1
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How to replace IR-block filter on *ist D

Folks,


I replaced the IR block filter of my *ist D to expand its spectral response to the far red and H-alpha line. This is very useful for astrophoto of emission nebulas.

I compiled all the info on the follwing web-page. Have a look if you are interested.

Pentax *ist D IR Mod ?(Enzo's Home?)

Ciao,

Vincenzo

02-10-2009, 01:18 AM   #2
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QuoteOriginally posted by vincenzomiceli Quote
Folks,


I replaced the IR block filter of my *ist D to expand its spectral response to the far red and H-alpha line. This is very useful for astrophoto of emission nebulas.

I compiled all the info on the follwing web-page. Have a look if you are interested.

Pentax *ist D IR Mod ?(Enzo's Home?)

Ciao,

Vincenzo
It would be really neat if Pentax would add a switch to add or remove the IR block. Not just for astrophotography but also for taking cool IR photos in the daytime or night photos with an IR flash.

Many in this group might think this is a silly idea and not attractive to enough buyers to make it worthwhile. Well, you might be wrong. After all, the IR switch and IR light on many Sony video cameras was a tremendous success for many years.
02-10-2009, 03:47 AM   #3
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Thanks for the article, Vincenzo.

Most interesting, clearly written and very well illustrated.

The *istD is sometimes not considered, because of its age, but I have one of the first ones sold here in my home town, and it's still going strong after more than 7700 actuations. Your photos provide some explanation as to why that is.
02-10-2009, 04:42 AM   #4
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QuoteOriginally posted by vincenzomiceli Quote
I compiled all the info on the follwing web-page.
Very interesting, thanks for posting.

I'd also be interested in the astrophotography shots you did with the modded camera.

02-12-2009, 03:08 PM   #5
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QuoteOriginally posted by Class A Quote
Very interesting, thanks for posting.

I'd also be interested in the astrophotography shots you did with the modded camera.
Sure,

I'm planning to add another page on the rest of the equipment like lens, guiderscope, guider, mount etc. and obviously some photo. I'll post the link here when ready.

Thanks,

Vincenzo
02-12-2009, 08:36 PM   #6
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correction??

QuoteOriginally posted by vincenzomiceli Quote
Sure,

I'm planning to add another page on the rest of the equipment like lens, guiderscope, guider, mount etc. and obviously some photo. I'll post the link here when ready.

Thanks,

Vincenzo
first, thanks, your braver then me....
One question: In the opening you say
"I knew that the Baader filter thickness of 2.7mm was larger than the Pentax own filter (I did see a report of *ist DS filter thickness of 2.2mm and I assumed it to be the same on the*ist D).
But then go on to say
"it is made of two glass plates one larger on the bottom and one smaller on top. These are IR and anti-aliasing filter. Total thickness is 1.2mm.
Am I missing something? Out of curiosity, I always assumed the AA filter was composed of 2 pieces. Cross axis... so the filter pack would be 3, though the 2 AA's could be bound together..... any hint of this?
Also:
I used 3 washers 0.7mm thick that I used to shim the CCD
plate

I assume that's one per screw not 3 for each..
Last is this correct? Where do you get the RI from?
Focus Plane Shift = ThicknessDifference * ( n - 1 ) / n with n being the refractive index of the filter glass
03-07-2009, 12:43 AM   #7
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Correction?

Hello Jeff,

the standard filter is made of two thin plates glued together. I can't tell for sure which is which. I think one is the AA and I can't tell if it is made by multiple layers itself (maybe doing a cross section?).

For the washers, yes it is one per screw.

I bougt the filter from David Hinds Ltd in the UK. Not sure who is the Baader distributor in the US but it should be very easy to find.

V.
03-07-2009, 10:52 PM   #8
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Vincenzo:

You are much braver than I!! I tried replacing hotfilters on a couple cheap webcams, following directions, and never got the focus right. I thought of replacing the hotfilter on a damaged Sony DSC-P10, but was intimidated by the complexity and my own clumsiness. My best results come with a Sony DSC-V1 'NightShot' PNS and various M&K/Hoya IR-pass filters, but such would not be suitable for astrophotography.

Sigma and Fuji both make dSLRs designed for simple filter replacement; Fuji markets theirs for forensic and scientific work. These systems allow for specific selection of IR-visible-UV spectra with proper filters. Everything costs, of course, but the cameras aren't that more expensive than a K20D - and no risky surgery is necessary.

03-08-2009, 05:23 PM   #9
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QuoteOriginally posted by vincenzomiceli Quote
Hello Jeff,

the standard filter is made of two thin plates glued together. I can't tell for sure which is which. I think one is the AA and I can't tell if it is made by multiple layers itself (maybe doing a cross section?).

For the washers, yes it is one per screw.

I bougt the filter from David Hinds Ltd in the UK. Not sure who is the Baader distributor in the US but it should be very easy to find.

V.
Alpine Astro

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07-02-2011, 01:11 PM   #10
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I bought an old *ist D camera and tried this.
I also try to enter Debug Mode to adjust focus, but I cant pass the Menu - Settings...

Now I regret that I didn't add washer...
07-03-2011, 07:23 AM   #11
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Thanks for posting this article, Vincenzo.
Good photos and instructions.
07-03-2011, 08:27 AM   #12
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QuoteOriginally posted by RioRico Quote
Vincenzo:

You are much braver than I!! I tried replacing hotfilters on a couple cheap webcams, following directions, and never got the focus right. I thought of replacing the hotfilter on a damaged Sony DSC-P10, but was intimidated by the complexity and my own clumsiness. My best results come with a Sony DSC-V1 'NightShot' PNS and various M&K/Hoya IR-pass filters, but such would not be suitable for astrophotography.

Sigma and Fuji both make dSLRs designed for simple filter replacement; Fuji markets theirs for forensic and scientific work. These systems allow for specific selection of IR-visible-UV spectra with proper filters. Everything costs, of course, but the cameras aren't that more expensive than a K20D - and no risky surgery is necessary.
Well, your primary tool is a dremel...
07-05-2011, 02:13 AM   #13
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Inspired by Enzo's comprehensive instructions I attacked my old Samsung GX1L with a view to converting it. The GX1L is a bit different inside (rebadged Pentax *ist DL) and the whole main board needs to be removed to get there. I adjusted the AF by 540um to get accurate results, so the shift for IR wavelengths is about 0.5mm using part of a Hoya R72 filter over the sensor. I didn't shim the sensor on its board since at the time I didn't know how much to shim it by, but with hindsight adding half a mm would have been good...

The various lenses I've tried have given mixed results.

The Sigma 10-20mm (f/4 version) gives poor IQ anywhere near the edges, although it is possible to focus it to give improved edges at the expense of the centre. It appears to be very poorly corrected in those wavelengths.

The Tamron 17-50mm is sharp at f/2.8 but upon stopping down it gives a marked central hotspot.

The kit 18-55mm (mark one version) gives excellent results, here's an example converted to mono:



...and this is leaving the false color in the image:
07-05-2011, 09:06 AM   #14
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QuoteOriginally posted by karma mechanic Quote
Inspired by Enzo's comprehensive instructions I attacked my old Samsung GX1L with a view to converting it. The GX1L is a bit different inside (rebadged Pentax *ist DL) and the whole main board needs to be removed to get there. I adjusted the AF by 540um to get accurate results, so the shift for IR wavelengths is about 0.5mm using part of a Hoya R72 filter over the sensor. I didn't shim the sensor on its board since at the time I didn't know how much to shim it by, but with hindsight adding half a mm would have been good...

The various lenses I've tried have given mixed results.

The Sigma 10-20mm (f/4 version) gives poor IQ anywhere near the edges, although it is possible to focus it to give improved edges at the expense of the centre. It appears to be very poorly corrected in those wavelengths.

The Tamron 17-50mm is sharp at f/2.8 but upon stopping down it gives a marked central hotspot.

The kit 18-55mm (mark one version) gives excellent results, here's an example converted to mono:



...and this is leaving the false color in the image:
That is very cool. I have a DL that I would like to do this to. Do you have any links to instructions? Did you cut up a standard lens filter to fit the sensor? How did you correct the focus? Is there a hack? Any info is welcome, Thanks, GP
07-06-2011, 03:56 AM - 1 Like   #15
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QuoteOriginally posted by gp1806 Quote
That is very cool. I have a DL that I would like to do this to. Do you have any links to instructions? Did you cut up a standard lens filter to fit the sensor? How did you correct the focus? Is there a hack? Any info is welcome, Thanks, GP
I started following Enzo's instructions, but it soon became evident that the 'D' and the 'DS' are very different. For the DL I found that the internals are pretty much the same as the DS, so I referred to this site to get more info. The main board has some slightly different connectors on mine but nothing too confusing.

Since I'm a cheapskate I cut an old Hoya 58mm R72 filter in half and fashioned the required 28x22mm filter out of one half. I wrapped the glass in vinyl tape except where I was using the glass cutter, then used pliers to snap it - luckily it divided cleanly.

The proper way to correct the focus is to shim the sensor so it moves towards the lens, but since at the time I didn't know how much to move it I left that so I could calibrate the focus after reassembly. Enzo's pages do cover that part, so in my case 0.5mm would have been correct. As it was I simply adjusted the AF via the debug menu. This means that the viewfinder image is slightly out when the sensor is correctly focussed, but that's not a serious handicap. You'd almost certainly need to adjust the AF a little in any case.

A warning - be very careful with the left side of the body when disassembled, there are high voltages on the flash circuitry which could hurt you or the camera. It is best to discharge these via a resistor before handling the body. You can get the service manuals for older bodies via the Pentax Hack site with good instructions on that step.

Be careful with the ribbon cables. Place the screws in containers and make notes about where they come from, there are around 26 screws of differing sizes to get as far as the sensor block. In order to separate the boards there are several tiny cables that need to be desoldered so make sure you know what goes where.

If you are not familiar with taking stuff like this apart you may well ruin it or hurt yourself so please be careful - or use a commercial service.
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