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Forum: Post Your Photos!
09-05-2013, 01:23 PM
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I did a number of additional experiments today with a wide range of focal lengths on two pinholes with the APS-C sensor. I won't bore you with the images, but my conclusion is, as others have also decided, it ain't worth the effort with this sensor.
When my wife let's me get a full frame, I may try it again. But that will probably be in some future lifetime.
Anyway, it was fun to play with and to try to optimize. I definitely learned a lot and would encourage others to try for the same reason.
The End
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Forum: Post Your Photos!
09-03-2013, 09:44 AM
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Taking the best result I had with the K100D Super, the 80mm pinhole, I got a very similar resolution using the K-5 body. See below.
So, while I could probably do more trial-and-error tweaking for the 46mm case, I think I'm close enough to go forth and see what kinds of effects I can get with these pinhole lenses. I will post anything I learn in this thread. One calculation I did in my head last night was that Near Infrared with a wavelength very roughly double that of green light at 550 nm should allow me to use the 80mm pinhole in a 46 mm configuration with NIR and get a reasonably decent approximation to best case resolution. I'll be trying that and posting results later.
And by the way, one thing I think I've learned thus far is that there is a fairly sensitive relationship between the pinhole diameter and the image resolution at minimal focal length (flange focal length being aroud 45.5 mm). So while I briefly considered purchasing a "precision" pinhole at 240 or 250 microns for the Pentax, I think one would have essentially the same issue: Having a precisely made pinhole diameter is no guarantee that that diameter is optimum for the focal length obtained with the cap and a camera body. My calculation suggests that at the flange focal length, around 220 microns should be optimal and you would have to have about 10mm extention to 56mm focal length for 250 to be optimal. The folks selling these don't seem to know what the offset of their product is from the flange contact plane. So I think anyone interested in playing with this will be better off with trial and error.
For now, here is the K-5 80mm result.
80mm-with-K-5-body by ChicagoJohn, on Flickr
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Forum: Post Your Photos!
09-03-2013, 09:22 AM
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My next endeavour was to take a second body cap and make a pinhole that would be optimized for 46 mm. I used the 3 mil 3M aluminum tape, cutting a 16mm square and "drilling" the hole with the tip of a #12 needle before taping it on the cap back, having marked the back with the dimensions of the square so as to place the hole in the center of the 3.5 mm hole I had drilled dead center in the cap.
I took successive shots of the same subject and each time slightly enlarged the hole. To do this, I needed to use a 10X loupe to get the needle into the original hole before slightly enlarging it. The first time I tried it without the loupe and wound up making a second hole. But eventually I think I got reasonably close to the resolution of the first one at 80mm, which I consider "acceptable". The first image below is cropped to the equivalent magnification ratio of 80mm for comparson with the last image posted previously. The second image is the full frame 46 mm image.
This is all using the K100D Super body. Next I'll look at the results using the same lenses on the K-5.
crop to equivalent magnification ratio of 80 mm for comparison
pinhole-at-46mm by ChicagoJohn, on Flickr
actual 46mm image
pinhole-46mm-full-frame by ChicagoJohn, on Flickr
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Forum: Post Your Photos!
08-29-2013, 11:31 AM
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I tried using a black Fotodiox body cap with a 1/4" hole drilled in it and a 1/2" square piece of aluminum tape on the back side (3 mil aluminum foil). After removing the adhesive with acetone (which also dissolves the cap plastic :), I used a #12 needle to make a hole. It wound up being about 300 microns by my visual examination under 10X magnification.
I then took three pictues of the subject using no extention tubes (flange focal length = 45.5 mm) and with 13 mm and 34 mm added to give about 59 mm and 80 mm, respectively. The theoretical optimum hole diameter for 80 mm is 300 microns. The first two images were cropped to give the same magnification factor as the 80mm image for a better comparison of resolution.
I am encouraged at the potential for sharpness when the hole diameter and focal length are dialed in. However, it's clear to me that using a pin to achieve a close match at the flange focal length will be purely a trial-and-error process. I may break down and buy one of the precision laser holes.
45.5 mm
pinhole-photo-f-45 by ChicagoJohn, on Flickr
59 mm
pinhole-photo-f-59-mm by ChicagoJohn, on Flickr
80 mm
pinhole-photo-f-80mm by ChicagoJohn, on Flickr
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Forum: Post Your Photos!
08-24-2013, 08:29 AM
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I couldn't find any smaller needles, but by putting one in a Dremmel Tool and then spilling the point on 400 grit wet dry sandpaper, I was able to put a finer point on it. The image below was shot with this smaller hole (perhaps not still small enough) and after sealing the extention tube segment better for light leaks. A marginal improvement, but I'll have to try experimenting using lens caps as you suggest. I'm getting some 3 mil aluminum tape to put over the hole in the lens cap. Then I'm taking solvent like acetone and removing the adhesive through the reverse side of the hole and then using still finer points on the pin to make holes in that.
This will be much better in terms of light leakage and a lot faster to change hole trials. I look forward to seeing your efforts and maybe together we can try to optmize.
I did happen to try my K-5 body in place of the K100D Super, and it was noticibly worse. I think that perhaps having fewer sensors (maybe larger or spaced further apart), could be better in this application. Just a guess based on what I have seen today.
After reading up on this on the internets, I found that 300 microns at a focal length of 45mm is about optimum, so I adjusted my hole size upwards and the the following may be close to optimum for my K100D. But I'm going to do more experiments when the body caps arrive.
Backyard-Pinhole-300-micron-at-45mm by ChicagoJohn, on Flickr
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Forum: Post Your Photos!
08-24-2013, 04:06 AM
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Thank you for the comment and suggestion. The f/number for my first attempt is ~ f/180 and the hole diameter is about 500 microns. I will try making another disk today if I can find a smaller diameter needle. I may try to thin the aluminum which is currently 0.16mm (6 mils) so that only the tip of the needle penetrates. I see they sell some at around 220 microns diameter, but I thought it would be fun to try to make something.
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Forum: Post Your Photos!
08-20-2013, 12:12 PM
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I used an aluminum pasta pan from Walmart and a thin leather needle to make a tiny pinhole in a disc I cut out with sissors and attached with double sided tape to the back of a 13mm extention tube segment. I checked it with a 10X loupe and then sealed up the slots from the front side with Gorilla tape strips.
At 1/2s in full sun that would normally have a 1/200s exposure for ISO 200 and f/16, the calculated f/number is around 180 for this hole; I don't know its diameter, but I'm gussing around 15 microns.
So I mounted the camera body on my Induro tripod on our deck and shot this picture of our neighbor's yard.
Pinhole-of-backyard by ChicagoJohn, on Flickr
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Forum: Post Your Photos!
09-03-2013, 10:17 AM
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While I still had everything out, I had to try the NIR experiment. The equation I've been using is optimum pinhole diameter in microns (mm/1000) = SQRT(2 * f * v) where f is focal length in mm and v is wavelength in nm. I've been using 550nm for green light. So, for example at a total focal length of 80 mm (flange focal length of 45.5 + 35mm extension tubes is about 80mm) with 550 nm, changing to around 1000 nm in NIR should allow you to cut the focal length in half with the same hole diameter. )I actually dreamed about this last night and did this calculation during the dream, so I had to check it out today. :)
I have a 58mm Tiffen 87 NIR filter that I have used in the past with the K100D Super. (Pentas has apparently added an IR filter in the K-5 so I've had no success there). And the filter just so happens to fit exactly when reversed on the Fotodiox body cap. All that was needed was three little strips of Gorilla Tape on the edges to hold it in place.
So here is the 46mm version of the same pinhole that appeared to be close to optimum with visible light at 80 mm total extention. I think this is a reasonably close confirmation of the rough calculation I did during my dream last night.
NIR-46mm-K100D-no-crop by ChicagoJohn, on Flickr
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Forum: Post Your Photos!
11-03-2014, 03:46 PM
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This was a test of my new K5 IIs to see what kind of resolution I might get with a full moon image. Oct 7. I like the dynamic range capability of this camera at over 14.
 Full Moon - Oct 7, 2014 by ChicagoJohn, on Flickr
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Forum: Post Your Photos!
11-04-2014, 06:30 AM
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This is a product shot of one of my wife's urns, hand-thrown from mica clay on a wheel, fired in a reduction atmosphere (raku), and fitted with a copper lid with an etched pattern. Having recently bought a K5 IIs, I wanted to see what sort of resolution of texture and detail we could achieve. I used a prime 50mm for this shot on a gradient background with one light on the left and a white reflector on the right. All comments, critique welcome.
 low smoke fired bowl by ChicagoJohn, on Flickr
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Forum: Post Your Photos!
11-03-2014, 05:08 PM
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This was taken with my K-5 kit that has all zoom lenses, the Pentax 55-300mm wr in this case, an excellent lens, shot with a monopod in the early morning just as the sun was coming up.
Shot in RAW, in post-processing, I moved the Clarity slider in ACR 8.6 all the way over to the left to create a decidedly soft effect and then played with the exposure sliders and vibrance and saturation to get this image which I felt was an accurate impression of what I felt in the crisp cold morning there watching the sunrise over the Fall foliage.
 Fall Color at The Morton Aboretum by ChicagoJohn, on Flickr
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Forum: Pentax K-3 & K-3 II
09-09-2014, 01:10 PM
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Since I started this tread, I thought I it appropriate to make this last post. I did return the K3 unopened to B&H who, we all know, are great folks to do business with, and they sent me a K5 IIS which arrived today. This was an actual, real-time decision process during which information came to light that I started out not knowing, or not fully realizing. And as a result of that process, a process which was by no means predetermined, I wound up not buying what I really, truly thought I would be buying when I started the thread. If anyone thinks otherwise, they are wrong. But whatever anyone may think, in departing, I want to thank you all yet again for helping me to gain a clear understanding of the facts and the trade-offs so that I could finally arrive at the right decision for me.
So that said, take care, and have fun.
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Forum: Pentax K-3 & K-3 II
09-04-2014, 10:13 AM
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I love cheese. But I don't like spam! However... maybe I would like cheesy-spam. And I love gaffers' tape too: I used to use it all the time when I was taking photography classes from the photography pundits at The Morton Aboretum; all of them quite famous, according to them. But then it was to cover the word "Pentax" on my K5. I'm sure it will work equally well on "Ricoh".
It's coming tomorrow, and I have a few experiments planned; though (and I can't see how they do this) the good folks at B&H told me they place no limit on shutter actuations during the 30 day evaluation period. Nonetheless, I will keep it to a minimum, especially in light of the glowing reports I've read about the K3 here on our wonderful forums. I'll post my results here in a week or so along with some pictures of wine, crackers, and cheeses of Nazereth, perhaps in B&W.
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Forum: Post Your Photos!
08-26-2013, 09:35 AM
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Hopefully this won't be totally inappropriate, but I thought I'd post a few examples of snapshots I made recently with the Pentax X-5. I got it to use as a substitute for my K-5 and associated gear (light and cheap versus expensive and heavy) for use in my new hobby of local flora identification. This is intended to give you a sense of what the camera is capable of when used in a hand-held snapshot mode in conditions marked by some rather signifcant breezes and plant motion.
It's been awhile since I've been on this forum, so if I have violated some norms -- number of images, content, etc. -- please let me know.
tall-sunflower-flower-close-up by ChicagoJohn, on Flickr
biennial-gaura by ChicagoJohn, on Flickr
hedge-bindweed-Open-Aug-15 by ChicagoJohn, on Flickr
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Forum: Post Your Photos!
10-22-2012, 05:15 AM
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The eyes have it in all three very poignant compositions;
My favorite would be the third in terms of the lighting and use of DoF and rule of thirds placement of the subject along with the V shape in the dynamic range coming in from left to right which, along with the hand; thumb and forefinger; all bring the eye very powerfully to the baby's face and smile.
Nice series.
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Forum: Post Your Photos!
10-22-2012, 05:57 AM
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This series is interesting to me apart from the great texture and the contrast and dynamic range from which the letters of the words arise.
But beyond that, because the mind habitually looks for meaning, I find mine being driven back to consider the very essence of language.
That is, there is a certain sense in which your series of images separate language from meaning; and this is a good thing in that it creates a pause in the on-going chain of cause and effect which comprises conventional reality and allow the opportunity, at least, for questions to enter the mind as to what the relationship between language and direct experience actually is.
And in addition to that, there is also the metaphor of "words carved in stone"; in this case powerful words, words assumed to have the most profound meanings. And ones mind can ask wherein those meanings arise; certainly not in the stone or in the light reflected from it alone. It's what happenes after that, isn't it?
As Neil Young observed....
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Forum: Weekly Photo Challenges
09-24-2012, 02:34 PM
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Forum: Pentax K-5 & K-5 II
08-26-2012, 02:41 PM
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The K-5 is like a D7000, only better :)
I can say this on our Pentax site, eh?
I can finally speak the truth!!
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Forum: Weekly Photo Challenges
09-02-2012, 04:09 AM
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Forum: Weekly Photo Challenges
08-29-2012, 04:44 PM
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I shot the following August 25, Saturday, during a photo outing at Cantigney Park in Wheaton, Illinois
Being new, I am not entirely sure how this context works, so let me know if I screw up.
All of these were taken with a K-5 and a Tamron 90mm macro lens.
Image #1
Image #2
flower close up by ChicagoJohn, on Flickr
Image #3
grasses and fountain by ChicagoJohn, on Flickr
Image #4
sunrise by ChicagoJohn, on Flickr
Image #5
bumble bee and spider web by ChicagoJohn, on Flickr
There ya go!
bumblebee closeup by ChicagoJohn, on Flickr
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Forum: Photo Critique
08-26-2012, 08:23 AM
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When to crop off the top off heads: (1) on a really bad hair day, (2) when the subjects are of the cone-head clan from Saturday Night Live, (3) when it improves the image to drop it down to below the subject's chins.
None of these criteria apply to the couple in question, and I would therefore agree with the majority that the entire head should be included.
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