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Old 02-20-2017   #1
Pec
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Default Newbee questions

Hi all

I am going to convert my fujifilm xpro1 to ir. Thinking of going with a 590.

A few questions

Will i still get sharp picture res? I hear 590 can impact sharpness.

I will set up a custom raw profile for LR, do i need to set WB in camera for eveyr scene? Will often be shooting desert so not a lot of greens.

Will the 590 allow me to shoot astro and see the red nebulas?

Thanks.

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Old 02-20-2017   #2
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The transmission characteristics of a 590 mm cutoff filter that you are thinking of choosing are much like the common Wratten A or 25 filter often used in old-fashioned black and white film photography. Such a filter will let in almost all of the red light and some of the yellows as well. It won't let in much if any of the true greens (about 520 nm) or any of the blues, violets, or ultraviolets though. I have heard of such a filter being used in place of a longer-cutoff filter for use with infrared film, which I would guess would give an effect much like a 720 nm cutoff filter - minus any color effects, of course - if my assumption is correct that such film is "blind" to red light as orthochromatic film would be.

On the other hand, silicon photosensitive devices are naturally quite sensitive to red and infrared lignt, somewhat less so to green light, and even less so to blue light, but these sensitivities can be adjusted with variations in processing the wafers and in external filtration. Besides the general infrared-blocking filter put in front of the imager in manufacturing, most such imagers also have a matrix of filters, one for each pixel, in a repetitive 2x2 pixel pattern, to allow for color differentiation. In the majority imagers, this pattern consists of two green pixels, one red one, and one blue one. Some imagers substitue use a yellow or "emerald" (yellow-green) pixel instead of one of the green pixels and some use a cyan-magenta-yellow (minus-red, minus-green, minus-blue) scheme instead, often substituting a green filter for one of the yellow ones. Then there is the Foveon® sensor that uses an entirely different color separation system, but those were limited to some early cameras manufactured by Sigma, to the best of my knowledge.

Assuming that you have an imager with red-greem-blue matrix, which is most likely the case, the red filter offers uninterrupted transmission throughout the infrared band, with the blue and green filters also transmitting from about 850 nm to the far end of the infrared band, plus their corresponding visible wavelength bands. During infrared conversion, the infrared-blocking filter is removed and is replaced with your 590 nm (and above) transmitting filter. This will block the blue light but allow some of the longer wavelengths of green to be transmitted. You are therefore left with four somewhat overlapping primary "colors" in your spectrum: yellow-green, consisting of those visible wavelengths to which your green pixels are sensitive and which the 590 nm filter still passes; red, which consists of those visible wavelengths to which your red pixels are sensitive; near-near infrared; consisting of those infrared wavelengths to which only your red pixels are sensitive; and general infrared at the long end, to which all three pixel colors are sensitive. In tabular form, your sensitivities are as follows, when the infrared filter is included for the imagers but not the eye:

Blue: R: No, G: No, B: No, Eye: Yes
Grn: R: Some, G: Some, B: No, Eye: Yes
Red: R: Yes, G: No, B: No, Eye: Yes
NNIR: R: Yes, G: No, B: No, Eye: No
GIR: R: Yes, G: Yes, B: Yes, Eye: No

From this, it can be seen that any "blue" response that shows up in your infrared image will be solely from the general infrared band (850-1200 nm) and the camera cannot distinguish between near-near infrared and true red, but the eye can. If you want to distinguish between these bands, you will need to take a second image, one with an external 720 nm filter on your lens and one without. You will also need to do a lot of color channel mixing and white balancing will be largely a matter of taste rather than anything objectively arrived at. However, a manual white balance on a green patch of lawn should give you a place to start. You can refine this later if you find a piece of black or dark red cloth that photographs as white under (general) infrared light - more common than you might think.

Infrared conversion can interfere with sharpness from a variety of causes, including diffraction chromatic aberration, and shifts in the optical path from the conversion process. Of these, diffraction is probably the least of your worries; nevertheless, it can still limit your sharpness if your system would be otherwise capable of very sharp photos. The overall wavelength of infrared light is something like 1.5 to 2 times the wavelength of green light to which the eye is most sensitive, with a corresponding limit in resolution in the infrared system aside from exotic things like deconvolution and apodizing the aperture. Before worrying about diffraction limits, though, you should concentrate your efforts on reducing other causes of poor sharpness first.

One of these is focus shift caused by the conversion process. One of these is the result of having different optical thickness between the original infrared blocking filter and the filter you, or more likely, the infrared converting service, replaces it with. A tech worth his salt doing the conversion will know about this and will make suitable adjustments in the length of the optical path.

Although errors from switching filters will be the same regardless of lens, differences from this particular cause will be the same for all lenses. This is not true for focusing errors as a result of longitudinal chromatic aberration which can also cause lens-dependent focusing shifts. Contrast mode autofocus should be able to compensate for this, but your focusing scale may be way off in its reading. You might also be able to use manual live-view focusing, but you may need to mount a neutral-density filter temporarily to get the aperture to open up wide enough in bright light and you might also need to go retro with a cloth hood to see your screen as the large-format view camera photographers do.

If I remember correctly, the red nebulae are red mainly because of the red hydrogen emission line at 656 nm, well within the spectral capability of your modified camera.
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Old 02-21-2017   #3
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Default Re: Newbee questions

Quote:
Originally Posted by Pec View Post
Hi all

I am going to convert my fujifilm xpro1 to ir. Thinking of going with a 590.

A few questions

Will i still get sharp picture res? I hear 590 can impact sharpness.

I will set up a custom raw profile for LR, do i need to set WB in camera for eveyr scene? Will often be shooting desert so not a lot of greens.

Will the 590 allow me to shoot astro and see the red nebulas?

Thanks.
Pec, you might want to have a look at this article by Dan Wampler of LifePixel - https://www.lifepixel.com/photograph...hy-super-color.

This one will also give you some insight into 590nm IR photography - My Descent into Infrared Photography, Part 3: One Camera, Multiple Looks | Educating Photographers, One Pixel at a Time?

Here is a gallery of 590nm images, so you can judge for yourself with regards to sharpness - Gallery of 590nm images .

I have a Canon 5D III that I had converted to IR with a 590nm filter and I love what it gives me. I have no problem with sharpness, except the usual things - OOF, DOF, etc. and that is usually when I start to get a bit sloppy with technique. If you shoot raw, and I strongly recommend you do, then you should not need to worry about WB if you set up a camera profile in LR. This is exactly what I do and of course you can always adjust the WB in post-processing (PP) if you feel a need to do so.

As far as astro photography goes, I am afraid I cannot help you there, as it is not something I have ever done, although, I have shot the Aurora Borealis in IR.

Hope this helps you make your decision. If you have any further questions, then post back and I am sure that someone here can help you out.

WesternGuy
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Old 03-09-2017   #4
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Default Re: Newbee questions

Hi there. I have a fuji XE1 converted to 590 filter. I have no complaints about sharpness but a lot of fuji lens give hot spots. You might have a look here:

X Photography: Fuji Infrared Lens Tests

If you check my threads, all the images are generated using the above camera conversion.
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Old 04-25-2017   #5
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Quote:
Originally Posted by fatoldbaldguy View Post
Hi there. I have a fuji XE1 converted to 590 filter. I have no complaints about sharpness but a lot of fuji lens give hot spots. You might have a look here:

X Photography: Fuji Infrared Lens Tests

If you check my threads, all the images are generated using the above camera conversion.
Ditto, I've recently had my XE-1 converted (Protech in UK). Early days but I'm loving what I'm getting from the shots.
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Old 04-25-2017   #6
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Another nice thing about fuji IR conversions is that the built in Filters that fuji includes give a great BW preview if both raw and jpeg (with one of several BW filters applied) are recorded.
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Old 04-26-2017   #7
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Originally Posted by fatoldbaldguy View Post
Another nice thing about fuji IR conversions is that the built in Filters that fuji includes give a great BW preview if both raw and jpeg (with one of several BW filters applied) are recorded.
Interesting. Thanks.
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Old 05-04-2017   #8
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Originally Posted by GeoffC View Post
Ditto, I've recently had my XE-1 converted (Protech in UK). Early days but I'm loving what I'm getting from the shots.
After watching video of a Laurie Klein workshop I was slightly worried when she stated conversion disables the in-built camera sensor cleaning.

On checking back with Protech, it seems with the XE-1, the sensor cleaning function is retained ...


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