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Forum: Pentax K-1 40 Minutes Ago  
What's the highest ISO you normally use?
Posted By photoptimist
Replies: 27
Views: 380
There's no fixed upper limit for me. The highest acceptable ISO depends on the slowest acceptable shutter speed and the widest acceptable aperture (for lens softness or DoF issue).

Sometimes, more ISO noise is better than more motion blur. Sometimes, more ISO noise is better than too shallow a DoF or softness from the lens.

That said, prefer to keep ISO at 3200 or below, do start to seriously think about the ISO-speed-aperture trade-offs if the TAv ISO value is 6400 or above, and rarely go above ISO 51200,
Forum: Film Processing, Scanning, and Darkroom 9 Hours Ago  
Dust removal technique?
Posted By photoptimist
Replies: 2
Views: 227
Personally, I would avoid rubbing a damp emulsion on a negative or print. The moisture will soften the emulsion, making it both sticky AND more prone to damage. Either a dry blower brush or a wet rinse (and drying the photo) would be better.
Forum: Photographic Industry and Professionals 10 Hours Ago  
Rant: camera prices and quality per format
Posted By photoptimist
Replies: 157
Views: 4,014
Total light does matter because it is differences in the recorded numbers of photons that let us perceive differences in the relative brightness of parts of the scene.

The central issue is that light from a scene is ALWAYS noisy even if the sensor is perfectly noise-free. The exact number of photons recorded in any given pixel in any given image is a Poisson-distributed random variable. The higher the expected or average number of photons, the better the ability to resolve adjacent differences in shading.

Bigger sensors with bigger pixels behind bigger lenses with bigger physical entrance pupils gather more photons which enable us to resolve more subtle differences in shading better than can smaller sensors with smaller pixels behind smaller lenses with smaller physical entrance pupils.
Forum: Pentax News and Rumors 1 Day Ago  
Ricoh's financial results for Q2 - Pentax still not doomed.
Posted By photoptimist
Replies: 184
Views: 7,516
It's not so much a "who cares" attitude by a "who pays for it" problem. The challenge with tests like that is in the high cost of buying a sufficient statistical sample size of camera bodies and building a test rig to use & measure the bodies.

That said, Roger Cicala at LensRentals does do copy variation studies of lenses and even some for bodies (Lens Rentals | Notes on Lens and Camera Variation). His company could easily gather data on how camera age/use impacts IQ. Each time a camera is rented, he could shoot a quick test shot when it was returned (part of confirming the camera is undamaged), compare the image to previous test shots over the life of the camera, and note how the months and shutter count affected things. But it wouldn't be perfect data for assessing the life span of MILCs because there's no way to tell if the user did 5 seconds of EVF time per shot or 5 minutes of EVF time (60X the usage of the sensor and electronics!).
Forum: Digital Processing, Software, and Printing 1 Day Ago  
Examine Single Pixel
Posted By photoptimist
Replies: 10
Views: 415
What do you mean "examine individual pixels?" Almost any image viewer can zoom in to 400% or more to magnify the pixels.
Forum: Pentax News and Rumors 1 Day Ago  
Ricoh's financial results for Q2 - Pentax still not doomed.
Posted By photoptimist
Replies: 184
Views: 7,516
They almost certainly do some testing to ensure that the rate of failure is less than some percentage threshold for the expected amount of use. How well those tests catch every type of failure under every pattern of use is another matter. BTW, Sony's warranty reserves run about 2% of hardware sales so if the average warranty repair costs 50% of the cost of the product, then some 4% of Sony products are failing within the warranty period. (If warranty fixes are cheaper, then the % rate of failure must be higher.)

Ironically, "accelerated aging" tests can totally fail to catch some types of problems. Back the 80s, some hard disks suffered "stiction" in which the disk head became stuck to the platter when the computer was off for a long time. That failure mode could never be detected by accelerated aging test because the failure was caused by non-use! The sticky solenoid problem on some Pentax cameras seems to be a kind of stiction issue, too. Casual users put their camera away for days/weeks/months at a time during which the solenoid grows sticky.
Forum: Digital Processing, Software, and Printing 1 Day Ago  
Cutting Photographic Printing Paper?
Posted By photoptimist
Replies: 23
Views: 516
One solution is to make the sheet sightly larger than needed and trim a fraction of a centimeter off the uncut sides. If all four sides are cut by the same cutter, the client won't notice anything.
Forum: Pentax News and Rumors 2 Days Ago  
Ricoh's financial results for Q2 - Pentax still not doomed.
Posted By photoptimist
Replies: 184
Views: 7,516
In principle, the EVF is the only added component but that doesn't mean a MILC is just a DSLR motherboard with a second display. Making a decent MILC requires a very high frame rate on the sensor, CPU, and graphics subsystems -- MILCs need more expensive chips than DSLRs to support a decent EVF experience.

As far as failure is concerned -- unlike a DSLR, using a MILC means running the sensor, CPU, and EVF full blast continuously. MILCs run much hotter than DSLRs and high temperatures are bad for electronics -- creating both component failures and connection failures from thermal stress cycling.
Forum: Non-Pentax Cameras: Canon, Nikon, etc. 2 Days Ago  
Canon says high DSLR demand may delay pro mirrorless body
Posted By photoptimist
Replies: 24
Views: 572
Exactly! MILCs for more than casual use have the same problem that has limited the adoption of AR (augmented reality) and VR (virtual reality). Lags of more than maybe 5 to 10 milliseconds tend to create discomfort in a significant percentage of users.

For photographers that spend a lot of time looking through the viewfinder, the frame rates of both the sensors and displays aren't high enough. Moore's Law can help on the display and processing side by miniaturizing these components. But Moore's Law can't do much on the sensor side. By definition, a full frame sensor can't be miniaturized and still be full frame.
Forum: Pentax K-1 2 Days Ago  
Pixel Shifted Images
Posted By photoptimist
Replies: 1,223
Views: 138,180
Diffraction or a soft lens limits the RAW image but can be conquered in post.

There are various clever mathematical ways to sharpen a soft image to undo the effects of diffraction or a soft lens. They involve analyzing and amplifying either the pixel-to-pixel value differences or the high-frequency components of the Fourier transform of the image. However, they also amplify noise in proportion to how much softness they try to undo. Overall, there's a strong trade-off between the sharpness of the image in the resolution sense and the smoothness of the image in the noise sense.

The key to success for these measurements is having lots of clean, high-resolution data which is what pixel shift provides.

Sharpening a Bayer filter image is really really hard to do because 75% of the pixel locations are missing data on red and blue channels and 50% of the pixel locations are missing data on the green channels. That is, most of the pixels are interpolated. Pixel shift fills in the gaps with more measurements and measures every green pixel twice which further reduces noise.
Forum: Pentax K-S1 & K-S2 3 Days Ago  
K-S1 topic: do people look down on you?
Posted By photoptimist
Replies: 28
Views: 463
That's the spirit!

What's that puny little black blob dangling from your neck strap? Get a real camera!

Forum: Pentax K-S1 & K-S2 3 Days Ago  
K-S1 topic: do people look down on you?
Posted By photoptimist
Replies: 28
Views: 463
A less charitable reply could have be: "Why does such brainless drivel come out of your mouth?"

If the person knew anything about modern Pentax cameras, they would know that the KS-1 is very capable of producing excellent images.

More importantly, if the person knew anything about photography, they would know that the gear does not matter that much.


Alas, there are some very shallow people in this world that think that only expensive things are good things and that all inexpensive things are substandard.
Forum: Pentax SLR Lens Discussion 3 Days Ago  
Opinion time: what are your favorite manual lenses?
Posted By photoptimist
Replies: 132
Views: 4,841
The Pentax 28/3.5 Shift is beauty and the beast in both form and function. Sharp and demanding, it can capture amazing images by forcing me to slow down.

The Super Takumar 135/3.5 M42 is swelte and crisp for telephoto work -- I need to use it more often!

And the Pentax MK 50/1.2 feels like two lenses in one: dreamy wide-open and retina-slicing sharp closed down. (Edit: it's the K 50/1.2 -- thanks, ChristianRock)
Forum: Pentax K-5 4 Days Ago  
November 11, 2019 Mercury Transit - Orange County, California
Posted By photoptimist
Replies: 11
Views: 437
The number of sunspots varies on a 11-year cycle. We're near the minimum right now so there are no spots.

See Solar cycle - Wikipedia for more.
Forum: General Photography 5 Days Ago  
Benefit of Mirrorless cameras with EVF -- 'Seeing' in black and white
Posted By photoptimist
Replies: 36
Views: 784
Isn't this feature already built into the human eyeballs of all photographers?

To pre-visualize a scene in black-and-white, my photography teacher told us to squint at the scene. Squinting reduces the light reaching the retina which reduces the signal coming from the color-discriminating (but less light-sensitive) cone cells and leaves the signal from the much more light-sensitive (but monochrome) rods cells. The result is nice strong impression of luminance contrast and pattern of the scene.

The trick works with all cameras, even ones with no viewfinder.

That said, a monochrome live view of the scene could be an interesting feature if the e-dials of the camera could be temporarily used to dial up/down the relative strengths of RGB in the conversion to B/W.
Forum: Welcomes and Introductions 5 Days Ago  
Mercury photography question & Introduction
Posted By photoptimist
Replies: 16
Views: 859
Nice!

I tried this projector approach for the transit of Venus a few years back. It worked but I did have issues with the sun burning the tracks and pits into the plastic inside the eyepiece when the sun moved out of the center of the field.:eek:
Forum: Pentax K-1 6 Days Ago  
K-1 MK2 Full Spectrum conversion for IR stuff
Posted By photoptimist
Replies: 33
Views: 2,729
If the filter is mounted between the lens and the subject, the distance-shift is between the lens the subject. If you focus on a nearby object and then put a 2-mm-thick filter, the plane of focus at the subject will shift by 0.67mm toward the lens. That wouldn't affect ∞-focus, thought because ∞ minus 0.67 mm is still ∞.
Forum: Photographic Industry and Professionals 6 Days Ago  
That's a damp squib
Posted By photoptimist
Replies: 25
Views: 886
Interesting and not impossible. But it does imply that the camera must change the exposure setting of the sensor every time your eyes move to bring that part of the scene (e.g., the bright lightbulb or dim black appliance face) into the DR of the sensor. When I look at that same high-DR scene that my eyes can clearly see in the OVF but try to use live view, I have a choice of setting the exposure for being able to see the details on the lightbulb (and most of the rest of the scene is unresolvable black) or boosting the ISO to see the appliance front (and the entire wall around the lightbulb is huge circle blinding-white with blinkies).

Note: there are HDR sensors being used in smartphones. But the quad-pixel technology creates some very strange motion blurring artifacts.

Except that this line of logic:
1) underestimates the costs of EVFs in added high-speed electronics and exotic sensors
2) overestimates the costs of the mirror reflex mechanism
3) assumes cameras are commodities -- people switch brands to save a few dollars
4) assumes camera buyers are unwilling to spend extra $$$ to get extra features.
Forum: Pentax K-1 6 Days Ago  
K-1 MK2 Full Spectrum conversion for IR stuff
Posted By photoptimist
Replies: 33
Views: 2,729
Those slip-in filters might also help your ∞-focus issues. Assuming they are made of glass, they will reduce the ∞-focus distance by 1/3 the thickness of the filter.
Forum: Photographic Industry and Professionals 11-09-2019, 02:35 PM  
Foveon always makes me excited
Posted By photoptimist
Replies: 57
Views: 1,317
Foveon's technology was quite seductive but it was doomed by the physics of silicon.

Foveon relied on the physical fact that shorter wavelengths of light tend to be absorbed near the surface of a silicon chip and longer wavelengths of light tend to penetrate deeper. By measuring photocharge at three depths inside the chip, the sensor measured light levels in short (e.g., blue), medium (e.g., green), and long wavelengths all in the same pixel. Thus, unlike Bayer mosaics, the sensor had data on RGB at each pixel.

HOWEVER..... the operative word on the absorption depth as a function of wavelength is "tend to." In reality the "blue" pixels captured lots of green and even some red light, the "green" pixels also captured lots of red and some blue light, and the "red" pixels captured some green and a little blue light Not only was the color separation poor relative to the engineered dyes of a Bayer color filter array, but the math to estimate RGB amplified any noise

Foveon's dynamic range and high ISO performance was competitive with early CCD and CMOS sensors but not with the more modern ones.
Forum: Photographic Industry and Professionals 11-09-2019, 08:56 AM  
That's a damp squib
Posted By photoptimist
Replies: 25
Views: 886
Exactly!

I, too, see room for both. Both designs has respective advantages and disadvantages.

For example, I doubt EVFs will ever reach the DR of an OVF. I was shocked when looked through the OVF of the M-1, noticed that my eyes could easily resolve details on both a lit lightbulb and shadowed black-fronted appliance and that those two surfaces were 17 stops different in light level! The human eye has about 20 stops DR but an EVF is limited by the DR of the sensor, processing, and display.

The parallels between the film vs. digital and DSLR vs. MILC battles seem tenuous. Film and digital really are very very different beasts as far as shooting, processing, and output are concerned. In contrast, DSLRs and MILCs aren't that different -- they use the same sensors, have the same resolution and IQ. Can anyone look at an image and tell if it was taken with a MILC or DSLR? And when you realize that a DSLR can act like a MILC but a MILC can't act like a DSLR, it seems strange to think that the camera with less flexibility is superior to the one with more flexibility.

What will be superior is a hybrid VF.
Forum: Photographic Industry and Professionals 11-09-2019, 07:38 AM  
That's a damp squib
Posted By photoptimist
Replies: 25
Views: 886
Their behavior makes sense given that bandwagons are social movements, not technological ones. And as a social movement, members measure their self-worth by the popularity of their choice. In the minds of the insecure (and it is the insecure that find the safety-in-numbers of a bandwagon so comforting), anyone who refuses to join the bandwagon is an outsider and an enemy.

For camera makers, bandwagons are seductive for their potential for high-margin sales but dangerous in that as a social movement, the bandwagon can fall apart or take a sharp turn in a different direction. If "the cool kids" suddenly decide photography is "soooo-2019," they'll jump to some other status-signalling hobby like kite surfing or skiing and leave last-year's MILC to gather dust in a box.
Forum: General Talk 11-08-2019, 06:24 PM  
Your latest acquisition
Posted By photoptimist
Replies: 17,797
Views: 1,212,838
Got a 10 TB hard disk (WD Red WD100EFAX) and a replacement power supply board for an old Apple Time Capsule (the original A1254 model from 2008).

I've had good luck upgrading Time Capsules with WD Red drives (both 4TB and 6TB models have worked in A1355 Time Capsules). WD Reds are designed for NAS applications and their 5400 rpm speed makes them less power hungry which is good because the Time Capsule's power board is a bit anemic on the 12V rail.

The new disk is up and running in the old box but it took me a good two hours to find, set up, and run one of my older computers that knew the password to this old Time Capsule. Haven't started the first back-up yet -- we'll see if the magic smoke stays in the box!;)
Forum: Pentax News and Rumors 11-08-2019, 03:02 PM  
New K-series DSLR under development to be exhibited
Posted By photoptimist
Replies: 3,487
Views: 222,438
So it's DPR reviewers, eh? No, wait, you said "trained" so it's not them. ;)
Forum: Pentax Film SLR Discussion 11-08-2019, 12:07 PM  
Post your B&W Film shots
Posted By photoptimist
Replies: 8,733
Views: 932,892
Nice!

That perspective reminds me of what a 12mm rectilinear lens does on the K-1. If you stand in the corner of a square space and shoot diagonally across to the opposite corner, the frame coveres all four walls. It's an interesting UWA composition for courtyards, street intersections, etc.
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