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Forum: Pentax K-r 06-10-2012, 08:42 PM  
Third Party D-LI109 Rechargeable Batteries
Posted By jdbosma
Replies: 24
Views: 9,976
I also picked up a no-name battery for my K-r. No problems at all. In fact it seems to last a little longer than the one that came with the camera. It was $20 with shipping. (April 2011.)
Forum: Troubleshooting and Beginner Help 02-18-2012, 06:11 PM  
Do you focus with eyeglasses on or off
Posted By jdbosma
Replies: 29
Views: 3,269
My prescription is -8 diopters in one eye and -10.5 in the other, so if I want to see *anything* through the viewfinder it's with coke bottles glasses on.

However, with advancing presbyopia, the only way I can use the LCD for focusing is ... glasses off!
Forum: Pentax K-r 12-03-2011, 12:03 AM  
pentax k-r
Posted By jdbosma
Replies: 8
Views: 1,616
Sure.
I should point out, as I tried to suggest, ("The issue is apparently due to ...") that I'm not 100% sure what the problem it. It's a conjecture, but I think a plausible one.

I got the idea from this thread on dpreview:
A Theory about Pentax K-R Front Focus Errors: Pentax SLR Talk Forum: Digital Photography Review
I also know just enough about optics to be dangerous, and the suggested explanation made some sense. However, he talks about the "wavelength sensitivity of the sensor" but what's more likely going on is chromatic aberration in the lens array that focuses light on the phase-detection sensor, not in the sensor itself. All known refractive materials have dispersion (the index of refraction varies with wavelength) and one reason that lenses have multiple elements in them is to use different materials with mutually compensating dispersion to reduce the chromatic aberrations of the lens overall. It adds a lot to the cost of the lenses, but there really isn't any other way. It would make sense for Pentax to design a less expensive, but also less well-corrected, optical path for the focusing system, which works well enough most of the time but could well have some sensitivity to the strong IR components of tungsten light. The upshot would be basically a calibration error that creeps in when the spectrum of the incoming light deviates from what it is designed for. (And it's also quite plausible that one of the added costs in a K-5 is a better corrected lens - I don't know the difference between "SAFOX IX" and "SAFOX IX+," but apparently they have the same number and arrangment of autofocus points, so there must be something else going on. It could be as simple as a coating that filters out the aberrated wavelengths, as suggested in the dpreview post.)

You can get a visual picture of how this looks in a nice graphic on this Stanford site:
Autofocus: phase detection

and while I'm at it here's another discussion on the same topic:
Understanding Camera Autofocus

to find more - a good search phrase to start with is "phase-detection auto focus"

The Stanford graphic shows the two light intensity peaks coming nicely together at focus, but that's an idealization and would require precise matching of the path lengths in the focus-sensor and image-sensor light paths - expensive, and not likely for a consumer product with strict cost targets. What almost certainly happens in production is that the camera maker assembles the components, then there is a calibration step to figure out what separation between the positions of the bright spots corresponds to focus. That gets turned into a number that is then recorded in the camera's calibration memory. (On the K-r and K-5, you can tweak it with options in the setup menu.) So that's why I wrote that perhaps the firmware could tweak the focus depending on the manual WB setting - it would be just a little bit of adjustment to the "in focus" separation between the light peaks. But whether they actually do that or not is pure speculation. I'd be a little surprised if they did, because it's likely to spoil more shots than it saves, but I don't have real information one way or the other. (if you take pictures with the wrong WB, that can be fixed, but if the wrong WB ruins your focus, that image is lost. And you are a mad customer.) On the other hand, some of people who have discussed this issue on these forums claim that they could detect a difference with a manual WB setting. (but then some claim they can't detect a difference, too.) On the third hand, I did some experimentation myself and what I mainly convinced myself of is that it is pretty tricky to get consistent results, and when people are looking for an answer that is buried in noise, sometimes they see what they want to see.

Anyway, whatever the cause, the surest cure is to get more light on the subject so that you can stop down the lens and improve DOF. No speculation required there.
Forum: Pentax K-r 12-01-2011, 09:54 PM  
pentax k-r
Posted By jdbosma
Replies: 8
Views: 1,616
The maximum aperture of the kit lenses isn't really that large, so the front-focus issue tends to be masked by the depth of field in many practical situations. That said, if you use maximum aperture and a relatively close subject under tungsten illumination, you might detect it even with the kit lenses. "Unusable" in tungsten light seems to me to be a little bit of hyperbole if we're talking about the roughly f/4 aperture of the kit lenses, but I don't have a f/1.4 lens so I can't test it out myself. Maybe a really fast lens like that is unusable.

The issue is apparently due to a wavelength sensitivity in the optical path of the focal system and the heavily red-shifted spectrum of tungsten illumination, compared to most fluorescent phosphors or to daylight. People claim that changing the white balance setting can help it. Maybe, maybe not. The wavelength sensivity is inherent to the materials used to focus light on the focus sensor, which can't be changed by altering white balance. It is possible that the camera's firmware could read a manual white-balance setting and introduce an offset to the "in-focus" signal from the focusing sensor in an attempt to compensate for the aberrated optical path, but I have a hard time believing that they would actually go to such lengths. If true, it would have to be from a manual WB setting - automatic WB can't be set until after the image has been acquired, at which point it is way too late to change focus. If you poke around the forum you can find a lot of discussion but not a lot of controlled experiments. (which are hard to do, I'm not trying to diss anybody's efforts, just pointing out the obvious.)

You can mitigate it by getting more light onto the subject, using brighter lighting or flash, so that the lens stops down and increases the depth-of-field. (Or use Av mode and set a smaller aperture, or Pv with a program-line shift to a smaller aperture - if you can tolerate the increased shutter time and/or increased ISO and noise.) If flash helps, it is because the extra light allows the lens to stop down a bit - the focusing still has to be done in tungsten light before the mirror lifts. By the time the flash fires, the focus has been set and frozen long before. Note, however, that mixing flash with tungsten light tends to produce unflattering white balance unless you correct it in post-processing. (An interesting experiment to try is to mount the camera on a tripod, in a room with tungsten illumination, focused on a neutral-colored subject, with the flash forced on and auto WB. Take a series of photos in Tv mode, varying the shutter from maybe 1/15 to 1/180. Assuming the room light is reasonably bright and the subject has average reflectivity, the camera will do a good job of maintaing the correct exposure. However, you will see a pronounced shift in color balance as the camera tries, but fails, to cope with the shifting proportion of scene illumination that comes from the room light and the flash.)

Also note that, if you use live-view mode with contrast-detection focusing, this focusing method is immune to the front-focus effect regardless of lens aperture. However, it is decidely slower than the phase-detection method that is used when you are using the viewfinder, and lots of people just don't like using the screen to frame and compose the image.
Forum: Pentax SLR Lens Discussion 11-23-2011, 04:16 PM  
Can you adjust for FF/BF with manual focus non-Pentax lenses?
Posted By jdbosma
Replies: 50
Views: 5,758
It's a different approach to the issue, but, if your camera has LIve View mode and you can use it, then there is no need to worry about front/back focus, focus trim, etc. On the K-r, and I assume many other cameras, Live View lets you zoom the image so that very precise focusing is possible.

I have used this technique (on a tripod) in some situations where focus was critically important and have been quite pleased with the results. For me it is faster and more sure than trying to use the viewfinder.

Hope it's not off-topic. The OP indicated that "correct focusing" was more important than "shown in the viewfinder."
Forum: Pentax K-r 11-19-2011, 06:13 PM  
Using AF/AEL button for focusing
Posted By jdbosma
Replies: 6
Views: 5,339
K-r lets you separate focus lock and AE lock. You use the shutter release for focus lock (press half way) and the AE/L button for AE lock only.
However, it is not the default - you need to change a setup option. It is on page 4 of the "camera" icon setup menu.

I much prefer this to the default setting.

You do need to remember a specific order of operations:
1) press shutter release 1/2 way to wake up the metering (and bring scene into focus if you are using AF)
2) center the part you want to meter on in the viewfinder (I almost always use center-weighted or spot metering)
3) press and release AE-L to lock exposure. A little asterisk appears in the viewfinder when exposure is locked. You
can press again to toggle exposure lock if you decide you didn't like it the first time.
4) now compose, focus lock if necessary, then shoot.

It takes much longer to read than to do. The main thing to remember is that pressing the AE-L button alone won't turn on the
metering system, but once you press the shutter release 1/2 way the metering will remain on for 10 sec. (Actually that is
adjustable too - "C" menu, page 1, option 4.)
Forum: Pentax K-r 11-13-2011, 06:49 PM  
Setting home town
Posted By jdbosma
Replies: 3
Views: 1,128
Posted in the K-r forum so I assume you are talking about the K-r firmware... I have one, so I know what you mean.
You are not picking your home town so much as your home time zone.
There appears to have been an idiosyncratic choice of multiple cities in some time zones, especially in Asia and Western Europe. It seems like one city per big country per time zone per continent, sort of... though that doesn't explain why some time zones have two cities in Australia, for example.
Not sure where you are posting from but they do seem to have every time zone covered, at least.

You can enter anything you want on the copyright screen!
Forum: Pentax K-r 11-13-2011, 06:26 PM  
Exposure With Neutral Density Filter
Posted By jdbosma
Replies: 4
Views: 1,707
Both explanations above are probably contributing to what you are seeing.

Remember, the exposure calculation has to be made before the mirror lifts. (You can't read out the image from the CCD and then adjust the exposure.... too late then.) Exposure metering is done, with the mirror down, by sending part of the light coming through the lens to the metering system instead of to the viewfinder. Unfortunately, that light path isn't one-way, so a portion of light coming in through the viewfinder can find its way onto the metering grid. Usually your face blocks any direct light entering into the viewfinder, but you are using a tripod, so the viewfinder is exposed to ambient lighting conditions.

Now you go and put a filter on the lens. A 10 ND filter cuts *a lot* of light. In ordinary conditions, the amount of light leaking from the viewfinder is insignificant relative to that coming through the lens. The filter altered that relationship by 10x - in effect, you made the viewfinder leakage 10 times greater.

so you wind up with two problems:
1) light from the viewfinder corrupts the exposure calculation
2) there is so little light anyway that the camera has a hard time calculating exposure - you may be getting near the low limit of the metering system.

Why does it work in Live View? In Live View, the mirror is up. Because the mirror is up, the regular exposure metering cannot be used once live view starts, and light cannot pass from the viewfinder onto the CCD - all the light comes through the lens only. The camera can moniitor the brightness of the images coming in and use that information to calculate exposure. Assuming you are using Contrast Detect focusing (or manual focus) the camera can get everything it needs from the Live View image.

I am not sure what would happen if you used Phase Detect focusing with Live View. In that case the mirror has to flip down for focusing. I do not know whether the camera takes exposure information from the Live View image just before you release the shutter, or from the usual exposure system during the focusing phase. Probably (in order to allow focusing on one spot and then re-composing the image) it gets exposure from Live View, but I don't know.
Forum: Pentax K-r 09-21-2011, 09:02 PM  
Pentax K-r Software - issue !
Posted By jdbosma
Replies: 6
Views: 2,256
Here is what works for me...
Look very carefully at the tabs in the upper and lower wing areas on the right and left of the main screen. Do you see one called "preview?" If so, click the "x" on that.

If you "x" the preview window when it is showing in the center area, it goes to one of the wing areas. If you "x" it in one of the wing areas, it goes back to the center.

I don't know why they didn't put it on the "display panel" menu. As someone else mentioned in this thread, this software isn't the most user friendly.

And, BTW, if you double-click one of the thumbnails, that should open in a window. Depending on ... I'm not sure what... the window might be another tab in the "area 4" or it might be its own floating window, possibly hidden behind the main application window. The image can take some time to display, as in about 10 seconds on my computer. I have a pretty slow computer, but don't expect instant results no matter what you are using.
Forum: Pentax K-r 09-10-2011, 08:44 PM  
Anticipation
Posted By jdbosma
Replies: 14
Views: 2,506
I guess I am one of those who feel more comfortable with a UV filter. Hope I don't scratch anything, but if I do, I'd rather it be the filter than the lens. Also, I find that sometimes people like to look at pictures, so I'll hand the camera to them. Not that many people are used to handling SLR cameras, and I've had them accidentally brush a palm or thumb across the front. Again, better to get a thumbprint on the filter than the lens.

However, my advice is: don't cheap out too much on the filter. I did, getting a cheap Vivitar filter kit with my camera. That was a mistake. The AR coating on the UV filter was not particularly good, causing high-contrast shots to have a very noticeable ghost image. Ugh. To make matters worse, the ghost was more noticeable in the captured images than in the viewfinder, so I didn't become aware of it until I had spoiled a couple of otherwise nice pictures.

Hoya HMC Super UV filter fixed that. $35, I think, but worth it. I wish I had bought that in the first place.

Hope you enjoy your K-r. I've been pleased with mine.
Forum: Troubleshooting and Beginner Help 07-26-2011, 08:54 PM  
Dead pixil
Posted By jdbosma
Replies: 3
Views: 1,817
Are you sure it is a dead pixel? A single dead pixel would be rather difficult to spot on most cameras. Also, if it is a dead pixel, it would likely have been there from the start. I'm not saying impossible, but if this developed over time, then it probably isn't a dead pixel.

Quite possibly it is a speck of dust on the sensor. This is a frequent problem with interchangeable-lens digital cameras. It is possible to clean it yourself if you have the correct tools, or most camera shops could likely take care of it for you (for a fee of course). Warning: DON'T try to touch the sensor with a Q-tip, Kleenex, or your fingers. Don't try to blow on it with your mouth. You WILL make the problem worse.

There is a post on cleaning here:
https://www.pentaxforums.com/forums/pentax-dslr-camera-articles/121739-those-...ur-photos.html

You can also readily find more information if you search on the Internet.
Forum: Troubleshooting and Beginner Help 07-16-2011, 08:13 PM  
White balance issues :(
Posted By jdbosma
Replies: 26
Views: 4,305
Have the images been cropped? The K-x has a multi-zone metering algorithm. If the original composition had a bright area that has been cropped out - for example a window in the background, or a sunlit white wall - that would control the exposure and could explain why this part of the image is badly exposed.

If what you have shown is the entire image that was captured, the camera's exposure system should not have a problem with it. You should not need any exposure compensation, never mind a couple of stops. If every picture you take has this kind of issue then perhaps something is out of whack with your camera's exposure metering system.

You should appreciate that "white balance" adjusts the relative gain levels of the red, green and blue color channels. The objective of white balance compensation is to make grays be neutral throughout the brightness range - presumably if that is achieved, then all other colors will be rendered more-or-less correctly as well. As enoeske pointed out, the problem with these images is more related to exposure than white balance. If you are trying to correct these images using white balance compensation, you are using the wrong tool.
Forum: Pentax K-r 07-06-2011, 04:56 PM  
Best pictures by newbbies with K-r
Posted By jdbosma
Replies: 1,046
Views: 257,934
I've been using this photo as my Windows desktop for several weeks, and I still like it, so I thought I'd put it up here. It's my first image posted.

This image was taken on the waterfront in Burlington, VT during an evening stroll. I was in the area on a business trip.

Aside from cropping and resizing, there has been no PP applied to this image beyond what the camera did. Unfortunately I had loaned the camera to a friend earlier in the day, and he returned it with the capture mode set to jpg... which I didn't realize, so I don't have the raw capture of this image. I would like to make it a little sharper, but even modest sharpening produces unpleasant artifacts around the highlights in the water and the contours of the ripples.




exif here if interested: Sunset and Duck on Lake Champlain - Pentax User Photo Gallery
Forum: Pentax K-r 06-20-2011, 05:40 PM  
K-r 1.10 Firmware on UK site
Posted By jdbosma
Replies: 56
Views: 15,811
As somebody already mentioned, the card doesn't actually need to be blank.
Nonetheless there is a very simple solution for your issue.

With the camera connected via USB to your computer (or using a card reader) ...
1) copy the picture folder from your SD card to any convenient folder on your computer.
2) delete all files and folders from the SD card (don't reformat)
3) install the firmware .BIN file on the root directory of the SD card

4) disconnect the camera and upgrade firmware per instructions

After installation completes, connect the camera to the computer again...
5) delete the .BIN file from the root of the SD card
6) restore the picture folder

This way you have an automatic backup copy of your pictures on your hard drive in the unlikely event that something goes wrong with the firmware upgrade. For this reason, even if you skip step 2, you should still do step 1.

If your pictures are valuable to you, you shouldn't rely on the SD card to store them anyway. In other words, you should be doing step 1 as a regular practice. And then, depending on just how valuable those pictures really are, consider archiving them to DVD-R, a backup hard drive, or some other secondary storage.
Forum: Troubleshooting and Beginner Help 06-12-2011, 06:02 PM  
Pentax K-r Status Screen: cannot turn off on startup
Posted By jdbosma
Replies: 2
Views: 3,511
You are shooting yourself in the foot. Set the Memory -> Shooting Info Display option to ticked 'on.' Press the Menu button once to back out of the option screen, then press the shutter release half way to get into the camera mode.

Also, you want the "Guide Display" switched off in the setup menu - sounds like you've got that already. If not, turn that off, then get back to camera mode.

Now press the 'Info' button until the screen goes dark. Don't press it again.

Now switch the camera off, then on. Blackness.

The Info button switches among three states: status screen, control panel, and blank. (See pg 25 of the manual.) The only way to bring up the control panel is to press the Info button when the status screen is showing. However, there are two ways to exit the control panel - either press the Info button, which sets the screen to blank, or half press the shutter release, which sets status screen. If you want not to have the status screen shown when you switch the camera on, then you have to make sure that it wasn't showing when you turned the camera off - in other words, exit the control panel by pressing the Info button. If you exit the control panel with the shutter release, you have set the status screen to show, and it will come on when you turn the camera on.

In the Memory menu, ticked 'on' means the camera remembers what you had set when you switched off; unticked means the camera restores the default setting when you power-on. For the status screen, the default is "shown," so un-ticking this option will cause the status screen to show all the time at power up.
Forum: Pentax K-r 06-12-2011, 07:07 AM  
New K-r - Display Screen Problem?? Need help
Posted By jdbosma
Replies: 14
Views: 3,984
> ywang


...and? Problem fixed?
Did your screen look like it was the same problem as redkr's?
Forum: Pentax K-r 06-05-2011, 08:16 PM  
New K-r - Display Screen Problem?? Need help
Posted By jdbosma
Replies: 14
Views: 3,984
Hi,
I have a pretty new K-r (not quite 2 months old)
I can confirm that your screen pictures don't look like mine, and yours don't look right.

The screen on this camera is actually superb, the nicest I've ever seen on a compact device short of an iPhone 4, and it would be as good as that if it were the same size. It is sharp, bright, colorful, and has practically no color shift if you view it at an angle. My guess is that you have a bad screen and you need to send it back for another.

However, there is one more thing you can try: I think you also have the old firmware. The giveaway is that on the info screen the date appears as "Sat 6/4 10:46 PM"
In the 1.01 firmware, the order of the date and day are switched, i.e. "6/4 Sat 10:46 PM."

Try updating the firmware. You can check your firmware version by holding the "Menu" button while turning the power switch from Off to On; if you don't have 1.01, you should update it. That's quite simple; start at this page:
Digital Cameras and Accessories - Official PENTAX Imaging Web Site
and follow the links until you get to the firmware download.

Also you might check the following settings:
- "wrench" tab, page 1, at the bottom: "Status Screen" -> 1 (selecting a different number changes some of the colors; 1 is the default and what you'll see in published screen shots)
- "wrench" tab, page 2, at the top: "Brightness Level" -> 0 (this controls the illumination level of the LCD backlight)
- also on that page, "LCD Color Tuning" - set the G-M and B-A offsets to zero (press the green button to quickly set zero)

Good luck. It's a nice camera and I've really been enjoying mine - in part because pictures look so good on the screen when you show them to people.
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