Pemihan
Well-known member
So Victor, is your 3100 converted to full spectrum (having a clear filter in front of the sensor instead of the standard IR cut filter)?
Peter
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Phase One IQ4 series. Much more than resolution.
- Thread starter dougpeterson
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So Victor, is your 3100 converted to full spectrum (having a clear filter in front of the sensor instead of the standard IR cut filter)?
Peter
ejpeiker
Member
You don't need to convert an IQ3100 to do IR, just the filter that he mentioned or similar and about 7 stops of additional exposure...
I posted a shot taken that way in the fun with Medium Format thread earlier this year - here's a direct link to the shot with all the image details (found in post 22315 in the thread)
https://www.getdpi.com/forum/attachment.php?attachmentid=131829&d=1516712222
Pemihan
Well-known member
OK, so you get a little window of IR between the 720 filter and whatever the IR cut filter on the back lets through?
I think this is correct. I’ve seen another photographer on Instagram do the same with his H6D-100c. Just put an IR filter on and you get whatever IR between the IR filter and IR cut filter let’s through.
ejpeiker
Member
Even with an 830nm filter, you can still get a usable image but exposures get long and focus is very difficult. At 715 you can still AF on high contrast edges but at 830 it's a crap shoot since AF no longer functions and you can't prefocus without the filter due to focus shift in the IR spectrum. So if you are serious about IR, either a conversion (not sure who I would trust to convert an IQ back
) or an Achromatic with the appropriate filters is the best way to go. If you go to the Fun with Achromatic thread in this forum you will find photos from DrPaul (a friend) who does a lot of this kind of work on the Achro back.FYI, I just posted another 715nm shot in the "fun" thread:
https://www.getdpi.com/forum/medium...-backs/4730-fun-mf-images-599.html#post766989
FYI I believe that P1 will do full-spectrum conversions on IQ backsEven with an 830nm filter, you can still get a usable image but exposures get long and focus is very difficult. At 715 you can still AF on high contrast edges but at 830 it's a crap shoot since AF no longer functions and you can't prefocus without the filter due to focus shift in the IR spectrum. So if you are serious about IR, either a conversion (not sure who I would trust to convert an IQ back
FYI, I just posted another 715nm shot in the "fun" thread:
https://www.getdpi.com/forum/medium...-backs/4730-fun-mf-images-599.html#post766989
dougpeterson
Workshop Member
Correct. We can deliver any back with or without an IR cut filter, and we can convert a back with an IR filter to one without.
It's a niche within a niche, but we have several clients with various IR-capable backs. Most commonly they convert an older back rather than trading it in for a newer back, but we also have sold a handful of IR-converted brand-new backs.
IR is a hobby of mine, and trust me, if you haven't done IR with a modern P1 back without IR filter then you haven't done IR this technically capable or enjoyable. The achromatic (without IR filter), especially, is crazy fun to shoot IR. I can't wait to use the IQ4 150mp Achromatic for this.
ejpeiker
Member
Doug, what are the cut-off wavelengths that are offered for conversion?
Peter.... I have a B+W 720 filter and that's all I use with my non-converted 3100. I don't go through all of the hoops with converting the file to DNG and then bringing into channel mixer etc. All of that never worked for me. There are two programs that will white balance my files correctly - C1 and Iridient. Camera raw is worthless. I find a grey area or place a grey card into the scene and balance on that. Everything turns to B&W except what is radiating IR. I'm left with those few colors to work with in PS when converting to B&W. I get nice light and white for the greens and nothing else is touched. I had intended to start a new thread for IR conversion but there isn't much traffic in that forum area.
I should mention that this is specifically for the 3100. I tried that same filter on my GFX and the results are much different. There is slight blue near the sky area and the greens are not as light as the 3100. Possibly the GFX needs a slightly lower strength filter - 650.....
Victor
dougpeterson
Workshop Member
Phase One does not provide this as a direct service. However, as a result of our work in CH (museums, libraries) where IR (and UV) are used for forensic discovery, we (DT) have the exact specification for the stock glass thickness and spectral characteristics and can provide that to our clients, in circular form, for lens attachment.
dougpeterson
Workshop Member
Clear or standard IR-cut.
You would then select the IR-pass wavelength you want as a filter in front of the lens. I suggest the Wine Camera Country Filter Holder. We can provide significant guidance here, from our in-house experience with IR Phase One.
Pemihan
Well-known member
Victor, Thanks for the explanation in your post above.
As far as I know Phase can supply the same as the original IR filter in circular form (77mm), at least it is in their price list. Also they supply the same filter in 100 x 100mm which I have for the Achromatic, so you could get that and use it with a filter holder.
What I'm particularly interested in for a normal color back is 550nm and for that I think you need to have the back converted to full spectrum, which is no big deal as it only involves replacing the IR filter in front of the sensor with a clear filter. Heck you could just remove the IR filter yourself if you dare (that would void any warranty), regardless you will have focusing issues but that's what live view are for, I use it all the time on the Achromatic.
Peter
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Pemihan
Well-known member
No no, it just become standard B&W with the IR spectrum cut off the same way as the color backs with IR filter in front of the sensor.
Peter
dougpeterson
Workshop Member
The item in their pricelist is the filter for the old scan back. It will do a decent job, but is not a 1:1 replacement for the filter used in modern backs. The difference would be more pronounced for color backs than for the Achromatic.
Pemihan
Well-known member
I'm pretty sure it is the same as the filters for the modern backs. At least that is what I was told and that they for some reason didn't change the name of the filter. I will see if I can dig it up in the support case where I got the info and Doug maybe you can double check in the mean time
Peter
Doug..... I want to make sure there is no miscommunication. If I have the IR filter removed from my 3100 I basically have an Achromat - or similar. If a duplicate IR filter is made to replicate the original filter removed from the Phase back then when attached as a regular circular filter it would allow me to take full color images. Remove it and the back acts as a B&W back. Correct?
Victor
dougpeterson
Workshop Member
Please PM me the name of the person in support that answered your case, as I'm fairly certain they gave you incorrect information. I'll of course double check my records as well in the meantime.I'm pretty sure it is the same as the filters for the modern backs. At least that is what I was told and that they for some reason didn't change the name of the filter. I will see if I can dig it up in the support case where I got the info and Doug maybe you can double check in the mean time
dougpeterson
Workshop Member
That is not correct. This is not how IR filters work. Maybe you're thinking of the Bayer filter (the RGB pattern)?