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Forum: Troubleshooting and Beginner Help 07-05-2009, 12:07 AM  
Autobracket feature on K200D
Posted By Quension
Replies: 4
Views: 1,671
The K200D doesn't have the one-touch AEB feature from the K20D, so unfortunately it's normal that you have to take each picture separately. I don't know why, I'd certainly like to have it...
Forum: Troubleshooting and Beginner Help 06-25-2009, 03:39 PM  
Firmware for K200
Posted By Quension
Replies: 11
Views: 3,899
You can reset the file number in the Record menu, Memory -> File No., although you'll have to change it back afterward to keep a sequential count. See page 213 in the manual.
Forum: Troubleshooting and Beginner Help 06-19-2009, 06:05 AM  
New K20D owner questions...
Posted By Quension
Replies: 8
Views: 1,966
The camera's preview sharpening is normal, and just the way it is. I find it annoying too, although I've heard people say the K20D's is worse than other models (I have a K200D). palidrom is right that you eventually are able to sense a pattern in it, which helps judge if an image is usable or not, so maybe there's some use to it...

The camera LCD is slightly different from most computer displays in that alternate rows are offset slightly, making it more sensitive to diagonals, but that's about it.
Forum: Pentax News and Rumors 06-18-2009, 03:16 PM  
"Battery Safety Firmware" - will others follow?
Posted By Quension
Replies: 21
Views: 4,921
Heh. Considering the various failure modes of poorly made Li-ion battery packs, it'd take casing nearly as big as the camera itself, and power transfer efficiency would drop a bit...
Forum: Pentax News and Rumors 06-17-2009, 06:40 PM  
HDR labs -Review HDR in K-7
Posted By Quension
Replies: 60
Views: 21,226
I know what you mean, but no, I'm not aware of any unique ID for a single group of bracketed images. I was envisioning software doing the grouping, as you say. I suppose the most reliable method would be to sort by ShutterCount, but apparently extracting that number requires some effort. I believe AEB avoids changing folders and such until the set is complete, so in practice just going by the number in the filename is probably good enough for any reasonable application.



Ah, that I understand. I have managed to produce some obviously unrealistic images using enfuse with some extreme exposures as input, but I too like it for the much more natural-looking results in general. The candy plastic of many tonemapping operations is rather distinctive.
Forum: Pentax News and Rumors 06-17-2009, 02:09 PM  
HDR labs -Review HDR in K-7
Posted By Quension
Replies: 60
Views: 21,226
interesting. care to elaborate on that? if it's there it can be used, it would normally just take me minutes to put something together.[/quote]

It's in the MakerNotes section, tag 0x0205 is the CameraSettings byte array; check bit 6 of CameraSettings[7] to see if it's in AEB mode, then look at CameraSettings[9] for the sequence numbers. The top 4 bits is this image number (0 = first), bottom 4 is the total number in the set.






QuoteQuote:

magical hdr raw? what are you on about?



"Magical" in the sense that it doesn't exist within the camera, not in general.



OpenEXR is not designed to hold CFA data, is it? Without that (and associated metadata) it's not a RAW format, and you might as well simply combine the bracketed RAW images on the computer as people already do; having the camera do it doesn't seem like much of an advantage. People complain about the lack of a single HDR image now, and lack of control over demosaicing, noise reduction etc will just be the next complaints on the list.



The source material is image data for a scene covering a large dynamic range: it most definitely qualifies as HDRI. Being contained and processed in slices instead of a single large blob is irrelevant, as HDRI has never been a definition of the individual processing steps.

You can certainly argue that the output is not HDR, which is of course technically correct, but as far as marketing and feature naming go that isn't terribly relevant either. The output is the result of an HDRI process, and in the common lexicon an "HDR image" is the LDR result of that process, despite being rather inaccurate. It's kind of like the "100% crop" shortcut...
Forum: Pentax News and Rumors 06-17-2009, 02:56 AM  
HDR labs -Review HDR in K-7
Posted By Quension
Replies: 60
Views: 21,226
There's already data in the EXIF about which images are part of an AEB set; if software's not using that now, it won't use a new tag either.

The problem with many of these "reviews" is that people see "HDR" and assume additive combining followed by tonemapping is the only possible way to get an HDRI result. The K-7 is not combining images into a single HDR dataset internally, then tonemapping and throwing away the intermediate result. It's doing exposure blending with the individual images, something that's more easily optimized and gives more reliable results than the myriad of tonemapping software out there.

Asking for the camera to write out a magical HDR RAW it's not even creating internally is futile ;)
Forum: Pentax DSLR Discussion 06-15-2009, 02:53 PM  
Auto focus points
Posted By Quension
Replies: 27
Views: 8,161
I wasn't that I thought the question was stupid (it's not); I was responding to a tone I thought I read in your original post. Nobody else read it the same way though, and they gave you useful replies, unlike me.

Sorry :(
Forum: Pentax DSLR Discussion 06-11-2009, 11:47 PM  
Auto focus points
Posted By Quension
Replies: 27
Views: 8,161
You're asking why people would like to use AF instead of MF?

...Seriously?
Forum: Pentax DSLR Discussion 06-11-2009, 03:54 PM  
Windows Mobile Pentax Remote
Posted By Quension
Replies: 25
Views: 9,614
Just to double-check: you did set the camera to the IR remote drive mode, right? (Fn, Up)

Beyond that I can't be much help, no mobile device to play with...
Forum: Troubleshooting and Beginner Help 06-11-2009, 12:20 AM  
Image Rotation
Posted By Quension
Replies: 16
Views: 4,638
Ha, neat, I never expected my K200D to handle upside-down. Not used to seeing the shadows from the built-in flash that way...
Forum: Digital Processing, Software, and Printing 06-09-2009, 09:32 PM  
Rewrite jpg's to many times? Degrade Pictures?
Posted By Quension
Replies: 19
Views: 6,404
I remembered, I just wanted to point out that some apps like XnView and IrfanView tend to blur the issue in terms of UI, and give some background for those trying to intuit what other apps might do.

I fully agree with your reaction though; basic tagging has nothing to do with changing image data, and it takes a special kind of dumb to conflate or ignore the issue when creating an application.
Forum: Digital Processing, Software, and Printing 06-09-2009, 03:49 PM  
Rewrite jpg's to many times? Degrade Pictures?
Posted By Quension
Replies: 19
Views: 6,404
That I am not sure on yet, been trying out iTag and XnView.[/quote]

iTag only alters the metadata; it will never degrade pictures.

XnView depends on exactly what steps you take. For the tags, you open the image and then Edit->Metadata->Edit IPTC data, Keywords tab. If you alter the keywords and then use the Write button on that dialog, it only alters the metadata, and there will be no degradation.

If you merely Apply and then close that dialog, followed by any form of File->Save/Export, it will rewrite the image data as well, and degradation will occur.



It's not more work, just different work. XnView is actually a good example; if the primary purpose of the app is viewing and conversion, then the image data and relevant metadata will be converted to in-memory formats on load and completely rewritten from scratch on save, according to the export/conversion format chosen.

Selectively modifying file metadata in-place for a specific format is a different task entirely, and is iTag's primary purpose. XnView accomplishes this by confining the task to the IPTC dialog itself. (IrfanView is similar.)
Forum: Digital Processing, Software, and Printing 06-09-2009, 02:57 PM  
Raw Conversion Software Recommendations Wanted
Posted By Quension
Replies: 18
Views: 6,940
This thread provides a bunch of software suggestions too, many of which handle RAW.




The gist of this is true (16bit TIFF preserves much more of the original image data finer steps, and is thus higher quality), but I'll add the technical note that the bit depth of RAW and converted formats are not directly comparable. In particular, a converted 16bit TIFF does not necessarily contain all of the data of the original 12bit RAW due to color space, gamma and white balance conversions. It certainly contains enough for all practical purposes though.

In general an editor that works in 16/48bit formats will allow you to make large changes while maintaining higher quality results, whether on screen or printing.
Forum: Digital Processing, Software, and Printing 06-07-2009, 07:12 PM  
Rewrite jpg's to many times? Degrade Pictures?
Posted By Quension
Replies: 19
Views: 6,404
I think the answer to your question is going to depend on what you're using to tag the files.
Forum: Pentax DSLR Discussion 06-07-2009, 03:55 PM  
Better pictures turn off SR?
Posted By Quension
Replies: 16
Views: 4,479
The review is actually from digitalcamerainfo.com, and I noted the same thing when I read that review some time ago. My first thought was that they're triggering the shutter without sufficient half-press time to let SR stabilize. There isn't enough information about that part of the test to know, and of course no full-EXIF samples to tell us for sure.

It's also possible the shake rig moves in ways SR isn't designed to deal with. Apparently they didn't have it when they reviewed the K10D, and they haven't reviewed any other Pentax DSLRs, so there isn't much else to go on.
Forum: Pentax DSLR Discussion 06-06-2009, 02:53 AM  
crazy thought about improving results from image sensors
Posted By Quension
Replies: 27
Views: 6,432
Whoops; at one point I thought that might be what you meant, but I was a bit rushed at the end of my last post and didn't think it through. Sorry!

One issue is that sensitivity for the colorless pixel would need to be different from the filtered ones; you would have to nearly triple the dynamic range to allow for complete white without losing sensitivity to pure green. Increased dynamic range is a goal sensor manufacturers are still chasing, and sticking with RGGB (or other individual color filters) would allow improvements to be applied to the entire image instead of being limited to subtractive color detection in part of it. It might not be considered worth trying until sensors can exceed our eyes' dynamic range and there is excess to play with.
Forum: Pentax DSLR Discussion 06-05-2009, 03:57 PM  
crazy thought about improving results from image sensors
Posted By Quension
Replies: 27
Views: 6,432
Unfortunately the hardware can't detect white. An individual photon has a wave frequency indicating its color in the light spectrum. "White" is literally a sum, a set of several photons representing a specific spread of frequencies in the right balance.

The hardware currently only "counts" photons to detect brightness, it can't tell what frequency they are. The color filters only let a specific frequency range through, but there's no way to filter white, since you need to examine the precise spread of frequencies of several photons in order to determine it is white.

The closest technology to frequency reading would probably be the Foveon sensor, which uses silicon refraction to move different light frequencies to different depths in the sensor. Foveon has problems of its own though, such as color bleeding; I suspect the problem is either that we don't yet know how to handle more frequencies with more precision, we know what needs to be done but the manufacturing technology doesn't exist yet, or it's just not remotely cost-effective at this stage.
Forum: Pentax DSLR Discussion 06-05-2009, 02:36 PM  
crazy thought about improving results from image sensors
Posted By Quension
Replies: 27
Views: 6,432
We've already seen examples of what happens, but to elaborate on why...



It's not to mimic our eyes' sensitivity, but rather to take advantage of it.

Our eyes are more sensitive to green light, which means we use it primarily to determine how bright something is. Relative brightness is how we detect contrast, the difference between light levels on objects or parts of objects, and thus detail in a scene. You can sort of see that to some extent on the linked page: in the single color images, there are always 2 crayons that are hard to tell apart, but it's easier in the green image than the others. (That's a lousy example because it's been through several levels of computer processing and display hardware, but try roaming around at night with one of those tri-color flashlights.)

That sensitivity is why early night vision systems output in green, and why red is often used as indication/incidental light at night -- since our eyes are less sensitive to it, our pupils don't contract as far, so it doesn't disrupt our natural night vision as much as other colors would.

The problem faced by the sensor is one of spacial resolution in color. If the sensor didn't have color filters, it would be great at creating monochrome images in high resolution -- one pixel of output exactly represents one pixel of light input in space. Since the filters are required to sense color, that means each pixel of output is missing two colors of input, and those two colors are lost at this point in space. The demosaicing part of digital processing basically takes each pixel and guesses what the other two colors should be.

The idea behind having more green pixels then is that they can be weighted for relative brightness on output. That will provide the most accurate local contrast for our eyes, and thus approximate spacial detail more closely. The color may not be perfectly accurate at each pixel, but since the brightness is more accurate our eyes will fill in the gaps and we'll see e.g. feathers instead of a smooth surface.



Actually, sensors tend to be most efficient at registering the red frequencies; there's usually a big infrared filter in front of the entire sensor. You'll sometimes see people complain about "the red channel blowing first" when they're trying to take pictures of things like bright red flowers, meaning the relative brightness wasn't that high but the sensor picked up so much red it saturated the image anyway.



The red and blue blotches are actually a result of processing rather than the noise characteristics of the sensor itself. Underneath the color filters the sensor itself is monochrome, and the noise comes from there and later analog stages in the sensing pipeline, so every pixel is equally noisy regardless of color.

What happens is that the demosaicing algorithm goes for local contrast by paying more attention to the green channel as mentioned above. When filling in the missing colors for each pixel, it translates much of the green channel toward relative brightness (luminance/luma) and the red and blue channels more toward color shift (chrominance/chroma). The noise present then takes on those two characteristics as well.

The result is that we see luminance noise as false contrast, or detail/texture, and our eyes are quite good at filtering that out when we look at a scene. Chroma noise shows up as the color blotches, which we find annoying because it changes the fundamental colors of the object we're looking at.

You can see an example of this processing in my K200D NR comparison post, in the bottom section, middle column. The raw converter I used doesn't do green weighting, so in the bottom image you can see the green pixels that result from noise in that channel. (And that there is roughly as much green noise as there is red and blue combined, matching the ratio of color filters on the sensor, showing that the noise is spread equally.) Above is the camera's JPEG engine, which translated many of the noisy green pixels into whitish ones, as if those were simply "brighter" areas of the scene compared to the base near-black area.

This type of processing has so far turned out to be the best general approximation of how our eyes view the scene the camera is trying to capture.






QuoteQuote:

SO, my thought/question was: what effect, other than obviously changing color balance, would result from using a red or blue filter on the lens at time of capture with a digital camera.



One of the most detrimental effects is a reduction in spacial resolution, as only 25% of the sensor area is being used to capture parts of the scene. As the others have commented, this also reduces the amount of light captured, and since the other sensor pixels aren't getting light they essentially read as pure noise. Standard processing that assumes the green channel is present just makes the results worse.

Hope that helps.
Forum: Pentax Camera and Field Accessories 06-04-2009, 02:57 PM  
battery grip question
Posted By Quension
Replies: 4
Views: 3,397
To be more specific, the K-m was not designed to support a battery grip: it doesn't have the extension contacts on the bottom that a Pentax-supported grip plugs into.

The third-party ones breischl mentioned for the K100D were designed with either cables or a side spar that plugged into the wired remote and DC input ports on the side of the camera. The K-m has neither port; the DC power option for it is a tray that replaces the internal batteries.

A creative designer might be able to set up a power tray that still holds some batteries, but since you can't control the shutter electronically, it's unlikely there will ever be any third-party grips.
Forum: Pentax DSLR Discussion 06-03-2009, 11:09 PM  
Congrads K200D!
Posted By Quension
Replies: 6
Views: 2,318
I saw this, glad someone else did too. Unfortunately I only had a couple minutes with the magazine, and the owner took it away :(

IIRC the check mark indicated a "great value" or otherwise something CR recommends, and the K200D was the only one with it in the entry-level DSLR category.

The K2000/K-m was also in that category, but placed quite a bit lower. Did you happen to see anything in the review text that explained why?
Forum: Photographic Technique 06-03-2009, 01:22 AM  
expose to the right?
Posted By Quension
Replies: 52
Views: 11,814
I was a bit loose in my explanations, so let's see if this helps...


I still dont' see where "more precise" comes from.[/quote]

Let's say the analog signal has a nominal range of 0 to 4V (AFAIK the real values are ridiculously small, but those details are beyond my knowledge), and the ADC's output is 12 bits (4096 values). Each output unit of the ADC therefore represents about 1mV.

We'll say the sensor is 2 stops underexposed, so the signal peaks at 1V. Only the bottom 10 bits of the ADC's output contain data, giving a range of 1024 values. Digitally amplifying this will still only leave us with 10 significant bits of image data.

Using an analog linear amplifier to boost the input to the ADC to peak at 4V will result in each ADC output value representing 250uV of the original signal, and the entire range of 4096 possible values will be restored. This is four times more precise than the same data digitally amplified.



I don't follow your reasoning here. What I meant with the 22bit ADC is that in theory that would be the perfect digital amplifier: the input signal is converted at maximum precision in one shot, so you can slice the 12 bits of output from any appropriate section of it without losing anything -- just chop off the bits you don't need.

(I don't know why the K10D had a 22bit ADC. Pentax was proud of it at the time, but I believe the later cameras are all using 14bit ADCs. Some web searching just now suggests the extra bits are oversampling primarily used to reduce noise from the sensor digitizing hardware itself, but I can't find an authoritative reference for that. The company that supposedly made the chips has mysteriously lost its web presence, and I don't have the engineering background to fill in the blanks myself.)



At least close enough to perfect that it can faithfully scale the weaker parts of the input signal to a range the ADC can handle, yes.



Right. In practice I gather this is mostly true for the lower ISO levels in many cameras, but higher ISOs are apparently dominated by both amplifier and sensor noise.

Also keep in mind that due to the logarithmic nature of the exposure, "half" is a significant amount for the darker tones (for how we perceive them), which are often important when push processing. The brighter tones aren't affected nearly as much because they have such a huge gradation range to work with from the start that we normally don't change them enough to notice any loss of precision.

(This is the point that's most relevant to ETTR.)



This is where the analyses by GordonBGood and Oleg_V come in. Sadly the details are still over my head.






QuoteQuote:

Like I said, for some reason I didn't quite follow your example, but it seems possible you are here saying the same thing I just did? That an analog amplifier *could* improve on digital, but the results actually depend on the specifics?



Yes. Using my new example above, let's say the median noise level from the sensor is about 250uV, and the amplifier is perfect. The least significant bit may then be rounded at ISO 100 and 200, but we can resolve the noise itself at ISO 400. Beyond that it wouldn't matter whether it was amplified in analog or digital form, because the brighter tones are already as gradated as we can resolve, and the darkest tones are buried in noise, so the bottom bits are useless anyway.
Forum: Pentax DSLR Discussion 06-02-2009, 11:19 PM  
Expected life span of the shutter mechanism of a K20D?
Posted By Quension
Replies: 18
Views: 9,234
It's recorded in the image metadata; see this thread for details.
Forum: Photographic Technique 06-02-2009, 03:53 PM  
expose to the right?
Posted By Quension
Replies: 52
Views: 11,814
Right!


text to satisfy minimum post length
Forum: Photographic Technique 06-02-2009, 12:56 PM  
expose to the right?
Posted By Quension
Replies: 52
Views: 11,814
Remember an A/D converter looks at a specific range of an input signal and quantizes it into a fixed set of values for output.



When you digitally multiply a value by 2 in binary, it is the same as shifting all bits one place to the left, leaving a new bit at the bottom. What would the digital amplifier fill in for this bit to leave it with a meaningful value?

E.g. if we start with a signal quantized into 12 bits at analog ISO 100:
000100101101
and digitally amplify it to ISO 800:
100101101xxx
the bottom 3 bits are meaningless because there no data to place there. The resulting data has exactly the same relevant range and precision as before. (It has less in actual terms -- it went from 12 bits to 9 bits -- but I'm assuming the top 3 bits weren't relevant before, so you only had 9 bits of useful data to begin with.)



Amplifying the signal in analog form results in the A/D converter having a different range to quantize, resulting in a different and more precise set of values on output. It increases the range of values represented in digital form relative to a digital amplifier, and by moving the bottom end of the range lower with respect to the input signal it removes rounding errors present toward the the middle of the range.

E.g. the new data might look like:
100101100110
where the underlined data was rounded in the earlier quantization at ISO 100. If the actual noise level was below that point but caused the rounding, the analog amplifier just gained you an extra bit (or more) of real signal to work with.

Now granted there are A/D converters with a much larger bit depth (like the K10D's advertised 22bit ADC), which makes the question more interesting with respect to camera internals. However, this problem remains for anything you would do in software outside the camera, because you only have the RAW file's bit depth to work with, and it is insufficient for significant changes in simulated ISO.
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