Category: Pentax *ist-D
I’m a big fan of infrared photography, and increasingly that means shooting digital IR. My personal setup has been based around a Pentax *ist-D 6 megapixel DSLR and a Hoya RM 90 filter. This has produced some pretty nice results, but it has some drawbacks. The RM90 blocks all visible light, and even infrared light up to 900 nanometers. As a result, exposure times on the *ist-D are fairly long. I also find a fair amount of “sensor flare” – light reflections within the digital sensor itself – when using the RM90.
Since just about everyone else who shoots digital IR uses a Hoya R72 filter, today I decided to pick one up and try it out. The R72 blocks visible light, but allows light transmission from about 700nm on. So I made a quick stop to the local camera store, which actually had them in stock, and then headed out to the Allegan Forest to run some tests.
Mother Nature did not entirely cooperate. Although the forecast was for clear skies and sunshine, by mid morning the sun was shining through high overcast clouds, and the only blue sky to be seen was in the southern half of the sky, which meant shooting into the sun to some degree.
Although I took several shots, I picked the one I liked the best and tried to make the best images I could from both the RM90 version and the R72 version. The photo of the Walnut Tree is the one I picked to work on. At the start of this post is the best shot I could make using the RM90 exposure. At the end is the best shot I could make using the R72 exposure. Granted – this test is a bit skewed. I’ve been shooting with the RM90 for a few years now, and have a lot more experience with it than with the R72 (used for the first time today.)
I’ve also enclosed the two RAW files, straight off the camera with no adjustment. These pretty clearly show the difference in color, white balance, and contrast between the two filters. If you look closely at the shot taken with the RM90, you can see some sensor flare in the form of a brighter cyan band running horizontal about 20% above the bottom of the frame. (Minor flare like this can be handled by using the sponge tool in Photoshop to de-saturate the flared area and blend it back into the rest of the image.)
Nonetheless, I shot several dozen images with the two filters, attempting side by side comparisons. Here’s a rundown of what I found out:
1. Speed – the R72 was consistently about 3 stops faster than the RM90. Throughout the morning I was shooting at f11. With the RM90 in place exposures were 2 to 3 seconds at ISO 1600. With the R72 exposures were 1/4th to 1/3rd of a second at the same ISO. In either case – a tripod was a necessity.
2. White Balance – When shooting RAW files, white balance can always be adjusted later. But it’s great to get it close to the mark during the actual shooting process. For a long time I just shot with the RM90 using either daylight or auto white balance settings. This resulted in a low contrast magenta image that could easily be adjusted in Adobe Camera RAW or in Photoshop itself.
These days, with the RM90 I just take a custom white balance reading, with the filter on the camera, off a white card. This results in blue skies that are deep burgundy to black, white clouds, and somewhat cyan colored foliage.
The R72 proved to be more of a challenge on this front. When the white balance was set to auto or to daylight, the camera produced a blood red image, with almost no discernable detail in it. (The detail could of course be teased out in the RAW conversion process, but with these white balance settings it was virtually impossible to access the composition on the preview screen.) I had heard that setting the white balance off foliage was one approach that worked with the R72, so I tried that out and set a custom white balance off green foliage with the filter in place. That resulted in a much better image – although it was still tinted orange
3. Sensor flare – sensor flare seems to be tied to the length of the exposure, and with the much shorted exposures from the R72, it was greatly reduced when using this filter.
At the end of the day, I can only say that the two filters simply represent two different sets of tradeoffs. The long exposures resulting from the RM90 can result in too much motion blur. The shorter exposures of the R72 help to address that – but I can’t see hand holding the *ist-D with either filter in place. Color balance is probably just a matter of taste - I can see liking the RM90 in some situations, and the R72 in others. It looks like the R72 will result in a lot fewer shots lost to sensor flare.
At any rate – I’m pretty sure that an IR converted camera is in my future, probably the near future to boot.
The drought has been continuing in southwest Michigan – though last night’s half inch of rain was a small relief. This past week temperatures in the mid 90’s F have only served to make the drought more acute.
On Friday I visited the Allegan Forest, looking for mid season dragonflies and opportunities for some landscape photographs. It must have been the oppressive heat, or perhaps the dusty dry soil, but there was nary a dragonfly or other insect to be found. For the first time in months I didn’t both with insect repellant, and not even a mosquito was to be found.
I decided to concentrate on shooting some digital infrared work. I’m seriously considering getting a dedicated digital IR camera – which unfortunately would mean moving away from using a Pentax since no one seems to do digital conversions of Pentax gear. But for now, I’ve been happy to work with the *ist-D and Hoya RM 90 filter.
Only one acceptable image came of the day’s IR shooting. This was shot at the edge of a restored section of Oak Savanna, right about where the deer can be seen in this shot from last summer. The image has been manipulated a bit more in Photoshop than I usually do, but the effect of increasing detail in some areas, while losing it in others, is interesting. Of course – the hot dry wind that made some branches wave during the 8 second exposure also had something to do the blurred areas of the shot.
This image was taken north of the Kalamazoo River. While there I took a few shots of one of the only large tree standing oak trees I’ve ever found in this so-called forest. Those shots were a disappointment – a plain tree, so what?
After working the areas north of the river for a while, I headed over to some familiar fields south of the river. I took the Allegan Dam Road, driving over the dam that backs up the river to make Lake Allegan. This turned out to be a scouting trip – it had been some time since I last drove along the dam – and I looked without luck for some promising areas in which to shoot.
After several visits to familiar haunts, coming up empty with regards to insect shots, I wandered down to the Ottawa Marsh. After all, if dry weather was the problem, than what better place than a marsh to find some moisture.
I saw quite a few bluet damselflies as I hiked down the dirt drive towards the board launch and the entry way to the marsh. Back in the marsh itself the effects of the drought were not as profound as in other areas. Of course – I was walking through areas that are probably knee deep muck during normal years - so that fact that the soil was still moist and vegetation as flourishing should be taken with some measure.
A ways in the marsh, following the river bank, I encountered an area of several acres thick with iron weed and joe-pye weed, all ranging from 4 to 6 feet in height. I wasn’t travelling light – I brought both the insect setup and the digital IR setup (complete with tripod) but I ditched the camera and tripod in a dense thicket, and wandered off into the iron weed.
Red spotted purples, spicebush butterflies, and more than a few giant swallowtails (lovely insects) were attached to the ironweed. It was difficult to get shots with a clean background - literally standing in flowering weeds as tall as me – but I managed a few good captures of giant swallowtails – to be included in a future insect photography update.
Wandering into a patch of vegetation that is pretty much growing over your head is usually not a great idea. Once you are ten feet into the patch, only your own trail leads you back out. But between the handy GPS system and noting a few large trees along the river, it was pretty simple to bee-line right out of the weeds once I was done shooting.
And from there it was a quick hop home.
Where do the dragons go when they don’t want to be seen?
Beats me, or else I would have seen some recently…
West Michigan’s unusual dry spell finally broke this last week. I visited the Allegan Forest on Sunday and again on Tuesday, both days after heavy local rains. It’s amazing how quickly the plants in the sandy soil of the pine barrens quickly turn from brown to green. The marsh I’ve been visiting off 48th street has progressed from dried, cracked mud, to muddy mud, to gooey muddy mud. Good sign for all the moisture loving creatures there.
But on both days, no dragonflies were to be found. A few spicebush and red spotted purple butterflies flitted about. So far this year, I’ve seen no Karner Blues, and it’s it’s likely I won’t see any this summer at all.
So I set my sights on landscape photography. In particular, I did some more digital infrared work using the *ist-d and Hoya RM90 filter. It seems that some of the best results are to be had on high overcast days. The few cool and dry, crystal clear days when I shot digital IR seemed to result in an undue amount of sensor flare and other problems.
The second image was shot last August from a similar vantage point as this shot, which was taken using Maco 120 format IR film in the trusty Pentax 6x7. Perosnally, I like the digital IR effect better – and while the digital shot required a fairly long exposure, it was not much longer than that required by the rather slow B&W film.
I also experimented with more ‘time and motion studies.’ These are 25 – 100 multiple exposure shots, building up a composite of light on the negative that bears no resemblance to the actual subjects shot. I realized that the Pentax Mz-S, with its capacity for unlimited multiple exposures, was the perfect tool for this technique. No results to show, but the studies continue.
My next opportunity to visit the forest is three weeks out. That’s disappointing, since a lot can happen in three weeks. But I’ve managed to carve out a few hours this Friday to visit the McLInden Trails, so with luck, a dragon or two might appear here in the near future.
As always, larger images and the full days shoot can be found in the image stream.