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Forum: General Photography 07-02-2020, 07:57 PM  
Do you know where your camera body cap is ?
Posted By JensE
Replies: 33
Views: 824
Mine are floating between extension tubes, bellows, tele-converters, a Pentax Program-A or sometimes just inside a lens mount cap - just never exactly where I need them.
Forum: Pentax SLR Lens Discussion 07-02-2020, 07:50 PM  
Is the Pentax D FA Macro 100mm WR the best macro option out there for my K1?
Posted By JensE
Replies: 22
Views: 1,246
You already have the most compact ~100mm macro. For me, the compactness is part of the fun shooting with the DFA100WR. As you're not concerned about working distance, a much wider macro would be fun to experiment with, rather than the more bulky longer macros. The 25mm or 15mm Laowas come to mind, or even their "probe" - if you can spare such an amount. Most of them however are fully manual, so you could as well just adapt/modify something you may already have - e.g. a reversed 28mm lens, maybe even on an entension tube. There are a lot of lenses that you can use with a bit of creativity, I e.g. recently used a projector lens with a Raynox in front, with excellent results ...


If you however like convenience, start with the DF-A 50mm f/2.8 macro (or predecessors) - fairly different rendering and already a noticeable wider field of view. Also handy when you quickly need to shift between macro and 'regular' distances, because 50mm is fairly universal.
Forum: Lens Sample Photo Archive 06-22-2020, 07:31 AM  
Carl Zeiss Jena Biotar 58mm f2 (M42)
Posted By JensE
Replies: 25
Views: 696
I tried (freelensing) - the lens would have to go into the mount for infinity focus, but the rear diameter doesn't fit the K-mount diameter, so it's limited to max. 2m. I'll see who I find for a CLA on the Praktina FX - still working but timing is off.
Forum: Post Your Photos! 06-18-2020, 04:01 PM  
Nature A few real tiny critters
Posted By JensE
Replies: 16
Views: 415
Superb. While I normally prefer some light on the background, the first one really lets the feathered antennae shine. The 4th is equally impressive yet sublime in its palette.

Any idea what we're looking at in those two?
Forum: Lens Sample Photo Archive 06-18-2020, 12:47 PM  
Carl Zeiss Jena Biotar 58mm f2 (M42)
Posted By JensE
Replies: 25
Views: 696
I have shot this quite a lot, but on on one of its native cameras, a Praktina FX. Is anybody aware of Praktina adapters/adaptability? The camera must be from early 50s, still just labelled 'Germany'.
Forum: Mini-Challenges, Games, and Photo Stories 06-17-2020, 03:03 AM  
The Monochrome Landscape - post yours!
Posted By JensE
Replies: 2,472
Views: 286,808
About the best 'pose' I could imagine. I prefer the 70mm perspective. I really like the monochrome versions better than the almost-monochrome color ones on Flickr though.
Forum: Lens Sample Photo Archive 06-16-2020, 06:22 PM  
Irix 150mm f2.8 Macro 'Dragonfly'
Posted By JensE
Replies: 96
Views: 4,464
A tiny wasp (I think), Irix 150mm f2.8 Macro 'Dragonfly' + HD Pentax-DA 1.4x AW teleconverter on a KP.
Forum: Mini-Challenges, Games, and Photo Stories 06-16-2020, 06:12 AM  
The Monochrome Landscape - post yours!
Posted By JensE
Replies: 2,472
Views: 286,808
Puff harder :-)

I really like the toning. Is this the natural vignette of the DA70?
Forum: Mini-Challenges, Games, and Photo Stories 06-15-2020, 02:12 PM  
Thematic Insects
Posted By JensE
Replies: 795
Views: 40,324
... 2.5mm long ant.


Admiring the giant ...

Cross-posted from the projector lens thread, however newly edited.
Forum: Mini-Challenges, Games, and Photo Stories 06-11-2020, 06:50 PM  
Thematic Insects
Posted By JensE
Replies: 795
Views: 40,324
@Mickmac - beautifully reduced palette, did you create/arrange the neutral background?

A look beyond 1:1 - a small ant at work among 'her' aphids.




I did experiment based on a recommendation to try a Trioplan lens for macro. This is a 'poor man's version' using a Diaplan projector lens, which I happened to have at hand, with a Raynox M 250 in front and a 'paper aperture' behind it. All hand-held in front of Auto-Bellows-K at full extension, resulting in 3:1 magnification. Portrait cropped to landscape, and then some. A little tricky to 'focus' as the daylight faded, even life view got noisier by the minute.
Forum: Lens Clubs 06-11-2020, 05:04 PM  
The "Projector Lens" Club ...
Posted By JensE
Replies: 457
Views: 122,935
... 2.5mm long ant. A matter of perspective.

Raynox 250 hand-held in front of a beaten Diaplan 100mm f/2.8 hand-held in front of an 8mm hole in roll film backing paper as aperture in front of fully extended K-Bellows and small extension tube for a 3:1 magnification, cropped to ~5mm field of view.
Forum: Troubleshooting and Beginner Help 06-11-2020, 01:59 PM  
IRIX 150 macro - stop down error - F value does not match?
Posted By JensE
Replies: 37
Views: 1,274
Maybe I should add that the above 1/3 EV is nothing to worry about for me at all. For critical JPG use, I would need to check the histogram anyway and for everything else, a +1/3EV more of "exposure" (raw value multiplier) doesn't matter at all, so I can use the Irix 150mm with the same exposure settings at f/2.8 as for all other settings.
Forum: Troubleshooting and Beginner Help 06-10-2020, 04:40 PM  
IRIX 150 macro - stop down error - F value does not match?
Posted By JensE
Replies: 37
Views: 1,274
Should be OK - high quality electronic ballasts, T-5 tubes, shutter 1/6s and slower. With electronic shutter, I can see the >20kHz flicker, but no slower changing component.
Forum: Troubleshooting and Beginner Help 06-10-2020, 03:39 PM  
IRIX 150 macro - stop down error - F value does not match?
Posted By JensE
Replies: 37
Views: 1,274
I redid the above test using more F-Stops, but only for minimum focusing distance and viewfinder, keeping exposure constant but closing up aperture in 1/3EV steps and increasing exposure time in 1/3EV each step. Results are displayed in a suitable log-log plot below.
I did a single test run only, but it gives you an idea about consistency of exposure once closed far enough, about 0.1EV, whereas f/2.8 is about 1/3EV below average and f/3.2 is almost in the error margin already.
(Just to make this clear - the vertical scale has an arbitrary starting point, '0' is not special. I could have put it from 5.0 to 6.0 - it's just meant to show the relative exposures in EV scale - i.e.log2-based.)
Forum: Pentax KP 06-10-2020, 02:40 PM  
Does anyone use lens correction?
Posted By JensE
Replies: 10
Views: 520
I actually like the KP JPEG engine and, in contrast to K-5 and K-1, tend to tweak things so that I can use the JPG out of camera for a lot of uses. Lateral chromatic aberration is on, the rest off, occasionally I turn on distortion correction for architecture in addition. Diffraction correction is off - I rather turn to the DNG if I need that level of detail.
Forum: Mini-Challenges, Games, and Photo Stories 06-10-2020, 07:52 AM  
Thematic Insects
Posted By JensE
Replies: 795
Views: 40,324
Well-fed larvae of different Lady Bird species.
Forum: Mini-Challenges, Games, and Photo Stories 06-10-2020, 03:35 AM  
The Monochrome Landscape - post yours!
Posted By JensE
Replies: 2,472
Views: 286,808
Amazing plan and result - just as the ones above.
Forum: Troubleshooting and Beginner Help 06-10-2020, 03:34 AM  
IRIX 150 macro - stop down error - F value does not match?
Posted By JensE
Replies: 37
Views: 1,274
They are engaging and get visible - as backed by the measurements. The initial step does look smaller than the following ones, though.


No, this was just a quick test using aperture priority - relevant when you want to know how the camera exposes with a particular lens at a given aperture. Checking the Light Value in the EXIFs, it does vary. I'll redo with constant EV tonight, when it is dark enough for controlled constant light.
Forum: Troubleshooting and Beginner Help 06-09-2020, 06:50 PM  
IRIX 150 macro - stop down error - F value does not match?
Posted By JensE
Replies: 37
Views: 1,274
I shot 4 different short tests series against a reasonably evenly illuminated white door, all in center-weighted average measurement mode, at f/2.8, f/4.0, f/5.6 respectively:

1. infinity, live view
2. infinity, viewfinder
3. MFD, live view
4. MFD, viewfinder

I measured a central area (376x432 - just for the simple math) of the raw files using rawshack and compared the Mean values (for Green_2, others are proportional) and also checked the visual results. In all four cases, f/2.8 came out visually darker than the other two (f/4 and f/5.6), which were very consistent (0.1%, 0.1%, 2.5% and 1.6% difference) to each other in each series. The f/2.8 exposures had 29% less (or -0.5EV) at infinity and 24% (-0.4EV) less at MFD, relative to the f/5.6 exposure - very consistent between life view and viewfinder.

For a comparison, I did the very same test with my D-FA 100 WR. At infinity, both the f/2.8 and f/4 exposures came out darker - by 10% (-0.16EV) and ~7% for both LV and viewfinder than the f/5.6. At MFD, only f/2.8 was darker, by 29% (ringing a bell?), and f/4 was actually brighter (~4.5%) than the respective f/5.6 exposures. Overall, the MFD exposures were significantly brighter than the infinity ones.

Somewhat surprised, I double checked the results visually using geeqie's 4-way view, zoomed in to the center at 1:1 to rule out vignetting effects. Visually, the appearance matched what I have calculated. If I find the time, I may put together some scripting to automate evaluation of the results and generate graphs for some of my lenses and maybe compare K-1 and KP.


In conclusion, there doesn't seem to be anythng out of the ordinary with my Irix 150mm.
Forum: Digital Processing, Software, and Printing 06-09-2020, 01:56 AM  
Megapixels vs Maximum Printing Size
Posted By JensE
Replies: 32
Views: 1,834
Sure the printer can't change the spacing of the nozzles on the printing head, resulting in a number of discrete resolutions that can be printed.
Forum: Troubleshooting and Beginner Help 06-09-2020, 01:44 AM  
IRIX 150 macro - stop down error - F value does not match?
Posted By JensE
Replies: 37
Views: 1,274
I have noticed - as stated above - that this lens meters differently (incorrectly) and has a tendency to overexpose, at the settings where I used it so far. As my exposures are often with aperture-priority, it's easy to compensate, so it's not a big deal for me. There may be something systematic about it.
Forum: Troubleshooting and Beginner Help 06-09-2020, 01:41 AM  
IRIX 150 macro - stop down error - F value does not match?
Posted By JensE
Replies: 37
Views: 1,274
This is what I'm wondering - is there maybe a different limiting diameter acting as aperture at close focus so that the aperture is not coming into effect until stopped down a bit?
Forum: Mini-Challenges, Games, and Photo Stories 06-08-2020, 06:28 AM  
The Monochrome Landscape - post yours!
Posted By JensE
Replies: 2,472
Views: 286,808
Light wasn't great until later, when I had moved on - colors were bad. But I do like it in b&w.



The Irix 150mm really delivers at infinity - I really like the textures and detail in the full-size version (linked).
Forum: Troubleshooting and Beginner Help 06-07-2020, 04:28 PM  
IRIX 150 macro - stop down error - F value does not match?
Posted By JensE
Replies: 37
Views: 1,274
My Irix 150mm has a tendency of overexposure too, but looking at today's pictures - mostly non-macro ones, it may be dependent on focus distance. Were your pictures at macro distances? Does it happen when focusing to infinity too? One hypothesis is that due to the change of focal length from internal zoom, the constant size of the aperture opening would mean a lower f-number, it may however only become effective after another limiting effect, when stopping down.
Forum: Photo Critique 06-07-2020, 04:40 AM  
Macro blown away..
Posted By JensE
Replies: 12
Views: 693
Your picture challenges that statement - most times, as in my case, it's definitely not the equipment, which sets the limits.

I'm using Rawtherapee a lot - but be prepared for a steep learning curve. New versions don't come for 32bit Windows versions anymore, but I have used RawTherapee - RawTherapee v4.2 for a long time.

Alternatively, there are occasional free offerings from commercial software vendors - typically their previous, but they do come with free perpetual licenses. I e.g. occasionally use DXO's software in some version that supports the K-5, but not newer models. A lot of those offers are reported here in the forum, so keep your eyes open. I'm not sure how you got your camera, but the Pentax software, which comes with it, can deliver very good results too and you can start from a very similar rendering as the in-camera JPG. Usability isn't great though.
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