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Forum: General Photography 6 Days Ago  
Things you see when you don't have a camera.
Posted By photoptimist
Replies: 22
Views: 875
It's well known that rare and fantastic creatures seek out camera-less humans to taunt. It's a variant of the fact that UFOs target solitary pick-up truck drivers on lonely back roads. Both are adult versions of having siblings that are angels when the parents are near and devils when the parents turn their backs!

Such are the mocking ways of the universe! ;)
Forum: Pentax SLR Lens Discussion 06-08-2021, 04:35 PM  
Lens for shooting Northern Lights with K-70
Posted By photoptimist
Replies: 15
Views: 585
Minor, but important tip: DO NOT USE ANY FILTERS ON YOUR LENSES!

The parallel surfaces of filters and perfect monochromatic nature of aurora light conspire to create concentric interference rings in the image.[https://jufa.medium.com/beware-newtons-rings-3cbfbd7228aa]
Forum: Pentax DSLR Discussion 06-07-2021, 11:01 AM  
K10D and "Hot" Pixels
Posted By photoptimist
Replies: 4
Views: 352
Great example!

In the astro world, this is a well known problem. This kind of noise doubles for every 6 to 8 C in temperature, is proportional to shutter time, and proportional to ISO.

The first line of defense is dark frame subtraction -- taking a second image with identical shutter time and ISO which is then subtracted from the primary image.

The second line of defense is sensor cooling -- hard-core astrophotography cameras often include refrigeration systems to chill the sensor and reduce the noise.

P.S. This physical property of silicon creates one of the disadvantages of mirrorless cameras. MILCs run the sensor at full power all the time to provide a nice viewfinder image but that makes the sensor hot.
Forum: Pentax SLR Lens Discussion 06-05-2021, 06:43 AM  
Cheap FF AF standard zoom: F35-135 vs FA28-70
Posted By photoptimist
Replies: 20
Views: 973
Nice reviews.

I'd think that BOTH lenses are essential to keep. For some subjects (big landscapes, tall buildings, small rooms), wider angle lenses are essential so you need the 28mm end. For other subjects (skittish creatures, sporting events, distant details), telephoto lenses are is essential so you need the 135mm end.

Of course, that pushes one toward getting a super-zoom (such as a 28-200) but then you end up with a bigger lens, slower aperture, and worse optical performance. Or one goes the route of a big bag full of primes to cover a full range of focal lengths but then you have to carry it all and spend time swapping lenses. ARGH!

One of the biggest challenges in photography is finding the right compromise(s) in focal lengths, apertures, size, handling, and cost.

(And it's all a great excuse for buying more lenses! ;) )
Forum: Pentax Q 06-01-2021, 05:27 AM  
Pentax Q with linear ultra-wide Theia SL183M 1.8-3mm f1.8 CS mount lens ?
Posted By photoptimist
Replies: 6
Views: 683
Nice lens!

The lens probably includes a relay lens inside it.

Normally a UWA requires lens elements that are extremely close to the sensor. For a lens that goes to a focal length of 1.8mm, the rear element would be significantly less than 1.8mm from the sensor. But that's not possible for C-mount/CS-mount due to the flange focal distance of 17.526 mm and 12.526 mm respectively.

Some UWAs use a retrofocus design to stretch the focusing point of the image further back. But retrofocus has it's limits. A 4X retrofocus (e.g., used to put a 12mm UWA on a 46 mm mount like Pentax K) wouldn't be enough for the Theia. The Theia lens needs something more like a 9 or 10X stretch to be compatible with C-mount.

For a really long stretch, lens designers use a relay lens. In a relay lens, the image from the main lens comes to a focus inside the lens barrel and then the relay lens captures the focused image rays and sends them further on. In doing so, the relay lens inverts the image relative to what the main lens created. For extremely long stretched lenses such as endoscopes and borescopes, the long pipe of the lens has a series of relay lenses.
Forum: Pentax SLR Lens Discussion 05-26-2021, 06:47 PM  
Pinholes Lenses
Posted By photoptimist
Replies: 3
Views: 431
Nice info!

A few more thoughts:

1) Optimal pinhole diameter: maximizing pinhole image sharpness means finding the Goldilocks sweet spot between bokeh blur because the pinhole is too big and diffraction because the pinhole is too small. The formula for the pinhole diameter with the sharpest photos this is 1.56*SQRT(F * Lambda) where SQRT is the square-root function found in Excel and scientific calculators, F is the focal length in mm, and lambda is the typical wavelength of light in mm (0.00055mm is green light). For the 50mm focal length of the Pinhole Pro, the best aperture is the 0.25 setting.

2) Using SR for hand-held shots: Sunny f/16 rule means that an f/200 pinhole needs a shutter speed of about 1.5 seconds at ISO 100 in sunny conditions. Push the ISO to 800 and you get a shutter speed of about 1/5th second. With a Pentax DSLR, you can use SR to stabilize hand-held pinhole shots -- just enter the focal length of the pinhole when you turn on the camera and it asks.

3) DIY: If you want to make your own pinhole lens from an old body cap, Making, Measuring and Testing the "Optimal" Pinhole: Pinhole Adventures Part 3 ? by Sroyon - 35mmc has a nice tutorial.
Forum: Pentax Camera and Field Accessories 05-24-2021, 08:14 AM  
Using step down rings with screw on filters
Posted By photoptimist
Replies: 11
Views: 543
The M 200/4 will probably be OK - maybe slight vignetting at f/4.

The 24/2.8 will almost certainly vignetting badly in the corners -- the corners may be correctable at f/2.8 but will probably be unusable stopped-down. Whether it works cropped 5:4 or 16:9 isn't easy to predict.

If you want to test things before buying the step-down filter, cut a hole in a piece of cardboard that's the size of the 49mm filter thread, stick a filter in the hole, hold the cardboard in front of the lens a take some test shots.
Forum: Digital Processing, Software, and Printing 05-18-2021, 06:39 AM  
How Many...
Posted By photoptimist
Replies: 48
Views: 1,628
No post processing for me, please.

I love being out in nature, traveling around the world, and taking photographs of whatever catches my eye. I don't enjoy sitting inside at a computer (I do that all day long for work).

Sure, post processing could make my photographs a lot better but it would make my hobby of photography a lot worse. Life is too short for hobbies that suck so I'm not going to do any post processing if I can avoid it.
Forum: Troubleshooting and Beginner Help 05-17-2021, 06:58 AM  
Light leak or lab mess up?
Posted By photoptimist
Replies: 17
Views: 636
Assuming this was B&W film, almost the only way to get a colored line is a flaw in the scanner (cyan = stuck red pixels in the scan head).

Check the physical negative for these artifacts.
Forum: Pentax SLR Lens Discussion 05-12-2021, 05:12 PM  
Impulse purchase
Posted By photoptimist
Replies: 18
Views: 991
Congrats!

Yes, it is a $20 hidden gem. I've ended up with two of them through camera purchases at garage sales. This lens is optically nice within the limits of their design.
Forum: Photographic Technique 05-12-2021, 11:57 AM  
Shutter speed while photographing children
Posted By photoptimist
Replies: 10
Views: 743
As @pschlute says, the required shutter speed depends less on the focal length and more on whether the active subject fills the frame. If active kids fill the frame (either with a telephoto lens at a distance or a wide-angle lens close up), then a fast shutter speed is essential to stop the motion.

But there's another strategy: embrace the blur. Use blur to show the action rather than freeze it. A slower shutter speed (maybe 1/60 or 1/125) and a combination of either timing the shot or panning to follow the action can create images where the child's face is fairly sharp and identifiable but the blur of limbs, balls, swings, and background shows the action. Learning to anticipate when the head or face are relatively still (and taking lot and lots of photos) can create powerful images that convey the energy of your children and their activities.

One of the huge advantages of digital cameras is that pictures are almost free (perhaps on a penny-a-shot) -- so what if you trash 99 bad images (or even 999 bad ones) in order to get a good one!
Forum: Troubleshooting and Beginner Help 05-11-2021, 05:59 PM  
K-70 time-lapse issues
Posted By photoptimist
Replies: 8
Views: 430
Exactly what settings do you use?

Is your interval between frames long enough? For a 20 exposure, you may need an interval of 22 seconds or longer. (The interval is the time between shutter presses, not the time the camera waits after the end of each exposure).
Forum: Pentax K-70 05-11-2021, 08:42 AM  
On Camera Fill Flash for Backlit Subject Outdoors
Posted By photoptimist
Replies: 18
Views: 754
First, you'll need to post an example or two (with EXIF) to get any good advice -- there are so many possible causes for this problem (metering, settings, JPEG settings, equipment, etc.) that it's hard to make good suggestions.

Second, getting good contrast with strong backlighting requires the best of lenses (usually not a zoom) in the best of conditions (no dust, scratches, haze, fungus, etc.) and even then it may not work. The sun is literally about 100,000X brighter than a sunlit scene and easily a million times brighter than a shadowed subject. Any scattering of the sunlight will wash-out the shadows.

(The simplest fix: avoid backlighting!)
Forum: Pentax Film SLR Discussion 05-10-2021, 02:09 PM  
I like a challenge...
Posted By photoptimist
Replies: 22
Views: 1,004
LOL!

Of course, with the long shutter times required for ISO 0.8, the reciprocity effects demand an exposure equivalent to ISO 0.4. But then the even longer exposure of ISO 0.4 requires a further reciprocity adjustment to ISO 0.2. But then ....... ISO 0.1, But then............

It's Zeno's paradoxical exposure -- it's never done no matter how long you expose it!

(In fact, the film is really just a strip of perforated clear plastic! ;) )
Forum: Pentax SLR Lens Discussion 05-09-2021, 07:41 AM  
General question, f2 vs f2.8 & other points
Posted By photoptimist
Replies: 27
Views: 951
A new body with one additional stop of high-ISO noise control will instantly upgrade ALL of your lenses by one stop. Moreover, better high-ISO often provides better images than do wider-aperture lenses. A wider aperture lens comes with shallow-DoF problems (e.g., only one part of one band member is in focus at a time) and wider aperture lenses tend to have worse edge/corner softness.

In the short run, a better body seems like a budget buster. In the long run, it's cheaper than upgrading a whole bag full of lenses.

The other option is to embrace the noise! Does anyone really expect an image from a dark music venue to be as smooth and flawless as an advertising product shot in a fully-lit studio? Maybe the grain in the image is part of ambiance.
Forum: General Photography 05-03-2021, 02:55 PM  
Why not Sigma L-Mount
Posted By photoptimist
Replies: 29
Views: 1,050
Four reasons:

Because so many people assume that new gear means better pictures -- if so, all the best photos and photographers in history are crap because they used "old" equipment.

Because so many people assume that "new" things are always an upgrade -- if so, paying a yearly subscription fee for software is an "upgrade."

Because so many people assume that "popular" things must be the future -- if so, McDonalds is the future of food.

The deepest reason is that there lots of people (equipment makers and click-bait bloggers) who make the money off getting people to replace perfectly good gear and they love to stoke the insecurities of camera buyers into believing mirrorless is the future.
Forum: General Photography 05-03-2021, 09:29 AM  
What lenses for 4x5 ?
Posted By photoptimist
Replies: 25
Views: 858
Many large format lenses use one of a few standard-sized leaf shutters. Mechanically-speaking, all the fragile tidbits of the lens (aperture & shutter) are in the interchangeable shutter. Other than fungus, balsam separation, or gross damage, not much can go wrong with the glass. Thus, if you get a used lens with a bad aperture or shutter mechanism, you only need to buy a replacement shutter.

Or, you could also go the pinhole route.
Forum: General Photography 05-03-2021, 07:26 AM  
Why not Sigma L-Mount
Posted By photoptimist
Replies: 29
Views: 1,050
But why would Pentax go mirrorless at all? The mirrorless market is very crowded now with Sony, Canon, Nikon, Fuji, and L-Mount. Why would Pentax want to become MILC-maker #6?

It's just like with cars -- just because more people want SUVs doesn't mean all people want SUVs and that all car companies should jump to making SUVs.

If anything, the seeming abandonment of the DSLR architecture by Canon and Nikon is an opportunity for Pentax to become the only choice for photographers who prefer an optical viewfinder for various artistic, aesthetic, ergonomic, and technical reasons.

Smaller makers of any kind of product will find more success by focusing on a niche (high market share of a small market) rather than being another me-too option in the most popular design (a tiny market share of a big market).

Pentax should maintain its differences rather than try to copy others.
Forum: Pentax K-1 & K-1 II 04-30-2021, 03:03 PM  
D-BG6 grip draining batteries
Posted By photoptimist
Replies: 21
Views: 853
There's at least four possibilities:

1) If the battery drained just sitting in the grip, that's almost certainly a faulty grip.

2) If the battery drained quickly during use, it may be a problem with dirty or damaged contacts on the battery, grip battery chamber, grip contact pins, or the camera's grid of contact pads for the grip. Faulty contacts would increase the resistance of the circuit, cause a voltage drop during high current portions of the shot cycle, and fool the camera into thinking the battery was low or dead. If this is the case, you might notice that a battery that was "drained" by the grip actually recharges quickly. That is, the battery wasn't really dead, it just couldn't deliver full performance. Try cleaning the contacts and check to see if the battery was really drained.

3) There's a slight chance the fault is in software. Pulling all the batteries and letting the camera sit for a minute might fix things. Or toggling the settings may clear the issue.

4) There's a slight chance the fault is in the camera. The only way to diagnose that is to get a second grip to see if it has the identical problem.

Note: If either the grip or the camera were actually draining the battery really quickly, the result would be a lot of heat and a high likelihood of a burning smell and smoke. A good sniffing around the grip, grip battery compartment, grip contact area, and camera might reveal that something is overheating.
Forum: Travel, Events, and Groups 04-29-2021, 10:32 AM  
traveling regrets with photography?
Posted By photoptimist
Replies: 19
Views: 781
My perennial travel regret is in not carefully studying all the sites I plan to visit to predict the best time of day to visit them. I'm always getting to some site and thinking -- this would look better at some other time of day. Of course, given limited time during a trip, I know I'll be unlikely to sacrifice the next site to revisit the first site.

That issue also leads to a bigger regret when I realize that I need to come back to a site on a different day of the year or come back during better weather (or after the scaffolding comes down). Yet I can't count on ever getting back to the site. Limited travel budgets and a preference to visit new things over revisiting old places means returning isn't likely.

Thus I know that I'm about to take a picture that could be better if only..... In the end, I'm often forced to take what I call "documentary" pictures -- images that document the fact I was there but which are of substandard quality due to the time-of-day, day-of-year, weather, etc.

I still love taking pictures but know that others who really can take the time to revisit a place multiple times to catch the best lighting, background, weather, etc. will have the better pictures.
Forum: Non-Pentax Cameras: Canon, Nikon, etc. 04-28-2021, 04:35 PM  
Graflex 5x7" SLR
Posted By photoptimist
Replies: 5
Views: 298
What a cool beast of a camera!:cool:

I'd bet the leather covering took the better part of a cow ;)

How many frames-per-secondhour can it do??? :lol::lol::D
Forum: Troubleshooting and Beginner Help 04-28-2021, 10:28 AM  
Ghosting? Whatever, how to avoid?
Posted By photoptimist
Replies: 14
Views: 485
Actually on a digital camera, a pinhole will create ghosts, too. Light from a bright spot in the scene will bounce off the silicon sensor, hit one of the surfaces of the glass and IR filter that covers the sensor, and bounce back. Sometimes it even creates a grid of colored ghosts due to diffraction off the rectilinear grid of traces on the sensor.
Forum: Troubleshooting and Beginner Help 04-28-2021, 10:22 AM  
Light leak, processing error, film problem or what?
Posted By photoptimist
Replies: 11
Views: 613
The fact that the leak extends well outside the frame on the negative means that it's not coming from the lens and shutter side of the camera.

The fact that the leak is once-per-frame, usually in about the same place means that it's probably the camera not the processing.

The fact that the leak appears on the bottom of the final image means it's coming from the top edge of the back of the camera such as a bit of missing foam or a slight warping of the camera back.

You might try opening the camera, laying one of the developed negative strips across the film gate, notice where the leaks line up against the top edge of the camera and focus your search there.

Good luck!
Forum: Troubleshooting and Beginner Help 04-28-2021, 05:27 AM  
Ghosting? Whatever, how to avoid?
Posted By photoptimist
Replies: 14
Views: 485
Ghosting is caused by light bouncing off one of the surfaces of the glass in the lens or camera, heading out the the lens, bouncing off a second surface, and then landing on the sensor. The solutions are:

1) Avoid very bright light sources in the frame or near the frame.

2) Get better lenses. Newer lenses with better coatings have less ghosting. Lenses with few elements tend to have less ghosting. But all lenses still have some ghosting -- see rule #1.

3) Avoid filters on the lens. Filters add surfaces and many filters have low-quality coatings. See rule #2.
Forum: Non-Pentax Cameras: Canon, Nikon, etc. 04-22-2021, 08:24 AM  
Tamron 11-20mm f/2.8 = Worlds First?
Posted By photoptimist
Replies: 18
Views: 726
Perhaps Doge is running Tamron's marketing department:

So aperture! Very Lens! Many zoom! WOW!
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