Digital IR

[Andrew O'Neill]

Andrew, I'll be very curious to find out how the 680nm filter works out. I expect it's give a good IR effect while being significantly faster than the R72.

I'll let you know!

[Audii-Dudii]

I hate to be a naysayer, but while I find Peter's photos visually appealing overall, to my eyes, they all appear to be noticeably softer than I would expect from my digital IR setup, which consists of a DIY converted, full-spectrum Samsung NX500 and various Contax and Contax N series lenses with a Hoya R72 filter mounted on them.

Because mine is a mirrorless camera and I would be using it exclusively with adapted, manual focus lenses, I didn't have to worry about any focus shift caused by removing the hot filter / cover glass assembly ahead of the sensor, so I simply removed it (along with the dust-shaker mechanism, which is part of the stack) and didn't replace it with anything. I did, however, take some test photos and adjust the sensor position very slightly using the factory's three spring-loaded adjustment screws to accommodate the lenses FFD (because a few of them have floating and/or aspherical elements, which are very demanding in this respect).

As a result of my modification (which, btw, can be easily reversed should I ever wish to do so), I can shoot (and do!) shoot handheld as well as from a tripod. With only one or maybe two exceptions, all y C/Y and Contax N lenses perform well at f5.6 and f8, with at worst, a very faint hot-spot that effectively mimics adding a very minor (1/6th stop) vignette during post-processing. Other families of lenses I've tried have not performed nearly so well.

But back to Peter's photos: My guess as to what's happening is that because he has to compose and focus without the IR filter attached, he's experiencing some amount of focus shift after he subsequently installs it. In the old days, this is the reason why lenses had IR marks on their focus rings, but these started disappearing once the first autofocus lenses appeared, so photographing in IR can be tricky when using a DSLR instead of a mirrorless camera, where this shift is not an issue because WYSIWYG.

FYI, one advantage to using an IR filter on the lens instead of mounted on the sensor is that it's possible to photograph full-spectrum, without using a filter at all. Although there isn't much IR light present from natural sources at night, there can be lots of it created by artificial light sources, so IR photography at night is definitely possible when using a dedicated IR camera.

Here's an example of a full-spectrum photo taken at night:



Personally, I like the soft glow that results from different frequencies of light focusing at slightly different distances, but YMMV.

And as proof that nighttime IR photography is possible, I offer the following examples:



The majority of the scene in the above photo s illuminated by a nearby streetlight and the different color temperature of the light mounted on the garage wall causes it to appear very different indeed.

and in this photo, the only source of light is the one mounted on the garage wall:



Finally, to address my original point, here's one of my handheld daylight IR photos, showing just how bitingly sharp an IR photo converted to B&W can be:



Note: It's not my intention to be critical of Peter's photos, assuming he achieved this look intentionally (IMO, it does work well for several of his photos), I'm only pointing out that if it wasn't intentional, different results are very much possible!Attachment 216561

[Peter De Smidt]

I hate to be a naysayer, but while I find Peter's photos visually appealing overall, to my eyes, they all appear to be noticeably softer than I would expect from my digital IR setup, which consists of a DIY converted, full-spectrum Samsung NX500 and various Contax and Contax N series lenses with a Hoya R72 filter mounted on them.

Sure. The main advantage of my system, for me anyway, is that I already have it.

I've photographed the railroad bridge with 8x10. Those photos have oodles more detail than my digital IR photos. I like my recent IR photos better.

[Tin Can]

Agree!

[Audii-Dudii]

Sure. The main advantage of my system, for me anyway, is that I already have it.

You'll get no argument from me on this point!

I've photographed the railroad bridge with 8x10. Those photos have oodles more detail than my digital IR photos. I like my recent IR photos better.

Hey, it's your photography, so you should photograph whatever you want and use whatever equipment makes you happy!

That said, I've noticed I have the same feelings about the majority of the photos I've taken with my 8x10 and my digital cameras. Which is that despite capturing significantly more detail, I also prefer my digital photos to my 8x10 transparencies as well!

[Peter De Smidt]

JG, it is a very good suggestion to check for focus shift. Most of my lenses have an IR mark, and a test wouldn't be hard to do, but it'll have to wait a week or so, as tomorrow I'm going on my first vacation in a very long time. My hypothesis is that I'm really using near infrared, and so there will be a smaller shift than if using an IR system that works at more true IR wave lengths.

[Audii-Dudii]

JG, it is a very good suggestion to check for focus shift. Most of my lenses have an IR mark, and a test wouldn't be hard to do, but it'll have to wait a week or so, as tomorrow I'm going on my first vacation in a very long time.

Lucky you! It's been more than a decade since I last had a real vacation and I don't see one happening any time soon.

My hypothesis is that I'm really using near infrared, and so there will be a smaller shift than if using an IR system that works at more true IR wave lengths.

You are very likely correct, especially as I don't know to which bandpass frequency the infrared mark on a lens has been calibrated.

Switching gears, I apologize for my initial post here. Reading it again just now (and also refreshing myself as to the intended purpose of this particular sub-forum), I realize I interrupted an on-going conversation and derailed it completely.

I don't know about you, but I hate it when this happens to me at parties and I hate it even more when I do it to someone else without realizing it!

I don't know if I can delete my post, but I'm happy to try doing so and/or to edit it and tamp-down my tone ... mea culpa! <blushes>

[Peter De Smidt]

No worries! You brought up some good issues.

[Andrew O'Neill]

I really can't see there being much if any focus shift with just the R72 filter. I've used this filter for decades on HIE, Efke IR, Rollie IR, and have never noticed any shift. I do however, see it with a wratten 87C opaque filter on HIE.

[Peter De Smidt]

Just got back from our trip. It was a lot of fun! Lot's of great stuff to see. I did find out that my Nikkor AF50 f/1.8D has a hot spot in IR the shape of the aperture. It's not large, and it shouldn't be hard to remove in post, but it's something to be aware of.