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Forum: Pentax DSLR Discussion
02-17-2009, 03:23 PM
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If the K20d liveview is any indication, the SR of the K20d would be wonderful for stabilization of video. The only downside is it makes a little bit of noise which might get picked up by the audio.
Bart
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Forum: Pentax News and Rumors
09-09-2008, 10:13 PM
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The key advantage of the 55-300 will be that it truly maintains 300mm F/L all the way down to the minimum focus distance whereas the 18-250 is closer to 100mm at the close end. So if you're shooting bugs and you want to keep your distance, the 55-300 will be significantly better (the 50-200 will be significantly better as well in this regard.)
I've also heard the AF speed of the 18-250 is slow. It might be (I don't know) that the 55-300 focuses faster if only because it probably has a simpler focuser which moves less glass when focusing.
Having fewer elements means the 55-300 might be a tad brighter and will have more dynamic range (less scattering between bright and dark areas of the image). And the 55-300 will have a hood that blocks flare better.
Robustness might be another thing. The 18-250 is very complex, perhaps over time it loses some IQ due to gradual misalignment of components. The simpler 55-300 design might be more robust over time.
Yet another consideration is bokah. Have no idea how they might compare here.
Of course none of this would explain anything about price--just considerations on choosing one or the other.
Bart
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Forum: Pentax News and Rumors
07-13-2008, 12:58 AM
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Like most others, I just want a big AF upgrade--faster, better tracking, maybe an F/2.8 center point.
I'd also like to have the ability to record audio annotations with photos--very handy when I'm trying to remember subjects names during events.
Of course any K30d-like camera must already be nearly through the development cycle (at least for the hardware) and into early qualification and test runs.
Bart
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Forum: Pentax DSLR Discussion
06-02-2008, 11:44 PM
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Yeah, seems like Sv is a lot like P after manually choosing an ISO. However, TAv is different from M mode in that there is an EV comp control in TAv whereas M mode simply provides direct access to the three parameters.
I think having auto ISO in M mode might be confusing--not only would it no longer be M mode, but you'd need to have the EV comp functionality show up somewhere. Also, there's more ambiguity in the behavior of the green button if you just had M mode with auto ISO.
On top of all that, the flash behaves differently in M and TAv modes--again, having separate modes is a good way to separate the behaviors.
Bart
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Forum: Pentax News and Rumors
04-25-2008, 01:21 AM
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I've been in there a couple times--they have the Pentax DSLR's and accessories. Citizen Photo and Advance Camera Repair are the other Pentax retailers in town I know of.
I recently got my K10d repaired at Advance Camera Repair they were able to talk Pentax into covering the repair under warranty even though it was a couple months past the 1 year mark.
Bart
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Forum: Pentax News and Rumors
01-19-2008, 08:04 PM
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Since they'd have to cut squares for the circular sensors (wafer saws must cut a straight line all the way across the wafer), then maybe they could integrate all of the support circuitry in the corners. So maybe there'd be no waste after all.
Bart
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Forum: Pentax News and Rumors
12-17-2007, 10:55 PM
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If the new camera has a significant improvement in AF speed (both low light and tracking moving subjects) to make it comparable to competitors (40D and/or D300), then I'd probably get a new body and perhaps the new 60-250 F/4 lens over the following months. Otherwise, I might just get that lens. I must say if the K20d doesn't have significant AF improvement over the K10d, it would shake my faith in the whole Pentax system a little bit.
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Forum: Pentax DSLR Discussion
11-21-2007, 07:36 PM
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I bought mine in January, and it's also made in the Philipines. How do you know how many shutter actuations?
Bart
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Forum: Pentax DSLR Discussion
11-07-2007, 10:45 PM
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Hi Lowell,
Just remember that having a linear response versus stops isn't actually linear--it's logarithmic. Ie., the number of photons that gets from 3EV to 4EV is twice as many as it took to get from 2EV to 3EV.
Bart
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Forum: Pentax DSLR Discussion
11-07-2007, 10:39 PM
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Hi Ray,
Yes, I agree. Aside from technical curiosity, I was pointing it out because the consequences of underexposing by, say, 1 stop aren't nearly as serious as they would be if the jpeg mapping were linear.
Thanks for posting that NuCore spec. It looks like they can apply gamma correction right after the A/D, so that means the K10d RAW files are probably even non-linear (which is a good thing.)
Bart
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Forum: Pentax DSLR Discussion
11-07-2007, 12:47 AM
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I'm pretty sure the 0-255 range doesn't map linearly to number of photons--it's a higher order mapping. So 128 is a lot more than 1 stop below 255--probably more like 2 or 3 stops.
The RAW image (12 bits) might be linear.
It's a little more complicated than that. SNR due to photon quantization isn't varying linearly with number of photons. It improves as the square root of photon count. There's also readout noise portion of SNR--that does go down directly with number of photons. The total improvement of noise will be somewhere between the two. As you get closer to the shadow end, readout noise becomes more significant and so you might observe SNR in the shadows almost increasing linearly with number of photons.
Doesn't change the correctness of your conclusion--ie., for lowest SNR, the farther to right you expose (without blowing highlights), the better.
Are you sure the camera even uses analog amplification to achieve higher ISO? At least on the K10d, I'd think with a 22-bit ADC and 16-bit datapath, there'd be no need for analog amplification.
Anyway, if it does use analog amplification, then you're right, you should theoretically get better SNR at higher ISO for equal exposure settings (f-number and shutter speed)--although the difference may be negligible if the noise from the sensor is already much larger than the ADC noise or other noise sources after the sensor. If it doesn't use analog amplification, then there will be no difference.
In my experience with the K10d, ISO1600 EV0 is less noisy than ISO800 EV-1, but it's also pretty obvious that in-camera NR has been applied--even to the RAW data. If you run both images through auto-profiling NR software to put everything back on a level playing field (eg., Noiseware), they come out looking virtually identical--both in terms of noise and in terms of detail retention.
Bart
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Forum: Pentax DSLR Discussion
09-30-2007, 12:28 AM
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Just keep the file index counting and remember the number of rollovers past 10k. It's not an exact count of shutter actuations (won't include multi-exposures or digital previews), but it's close.
Bart
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Forum: Pentax DSLR Discussion
09-25-2007, 11:45 PM
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The relative versatility of the lenses depends on if you need telephoto more often or better closeups more often. Quality issues aside, both the minimum focus distance and max magnification of the 17-70 are significantly better than the 18-250.
In my case, I really need my all-around lens to have essentially no limit on how close the subject can be and it needs to have as much magnification as possible (both for shooting my kids and the variety of nature photography I like to do).
Occasionally (quite rarely really), I wished my 17-70 would go past 70mm. But not as often as I need to be a few inches from the subject (especially at wide angle). So the 17-70 is the better all-around choice for me and minimizes lens changes more than the 18-250 would.
If you don't really do closeups that much, or you are fine having to change lenses for better closeups, then the 18-250 might be the better choice. The 18-250 is the obviously better all-rounder for someone who does a lot of animal photography mixed in with general snapping.
The only other thing to consider on the 18-250 is the precipitous drop in magnification for closeup subjects. For instance, the Pentax DA 50-200 has the same magnification at 1.1m that the 18-250 has at 18in. In other words, at 18in subject distance, the 18-250 only goes to about 100mm equivalent FOV. So if you're using the telephoto for sneaking up on nervous bugs or small birds, the 18-250 won't necessarily obviate the need for a conventional telephoto lens like the 50-200.
Bart
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Forum: Pentax DSLR Discussion
09-07-2007, 01:44 AM
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GX10 doesn't shoot compressed RAW. So you'll have to buy an extra ~40% of flash memory if you shoot RAW a lot.
Bart
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Forum: Pentax SLR Lens Discussion
08-20-2007, 10:03 PM
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The Sigma 17-70 is MUCH better at macros. Not only is the max magnification quite a bit higher, but the kit lens local contrast starts to deteriorate at close distance and max F/L whereas the 17-70 stays sharp.
Bart
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Forum: Pentax DSLR Discussion
07-31-2007, 11:47 PM
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1. Faster/better low-light auto-focusing
2. Higher flash sync speed--especially with the built-in flash which doesn't do HSS.
3. SR stays on for a little while after releasing the AF button (several seconds is sufficient). This way you can rev-up SR so it's instantly ready even if I have to take a quick shot. This could be done with a FW upgrade to the K10d.
4. More sophisticated matrix metering--like a 500 or 1000 pixel array. I presume this would also enable spot metering at any AF point--not just the center one. Maybe would also help P-TTL exposure be more dependable.
5. Fix the vertical banding issue.
Couple of unreasonable or pro features:
-Predictive AF.
->5fps shooting
-Shake Reduction for the AF sensor (should improve performance at long FL).
-"Best image" selector. If I take 10 nearly identical shots, the camera chooses the sharpest one and tosses the other 9. It's a good compliment to SR. Nikon might have this one sewn up in a patent.
Bart
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Forum: Pentax SLR Lens Discussion
06-17-2007, 08:13 PM
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It sounds great, but I assuming the brighter lens would have to be physically larger and thus more expensive. And since the IQ of the Tamron is reportedly quite good (even besting the Nikkor 18-200), Pentax would have to at least beat that and thus the cost goes up more.
But if they can somehow overcome all that, I think it could be a winner--even at >$800. It's hard to say how much that market segment would be willing to pay for a lens (remember, customers of this lens would probably tend to NOT be professionals, so price tolerance is lower.)
Perhaps another way to one-up the competition would be to intentionally increase the physical length another few mm so the macro magnification could be higher.
Bart
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Forum: Pentax DSLR Discussion
05-24-2007, 01:03 AM
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It's irrelevent to this discussion, but FYI, 72 dpi is a typical dot pitch for computer monitors. Some programs do read the dpi value. For instance MS Word will scale the display of imported images according to the dpi value (higher DPI means the image is displayed smaller). A value of 72 dpi tell MS word to show the image at 1:1 size.
Bart
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Forum: Pentax DSLR Discussion
05-22-2007, 08:57 AM
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I was looking at how that pin works on my 540 and the lock pin doesn't fully retract until the lever is all the way to the left--there's a slight detent. I wonder if people have maybe not quite pushed it all the way in such that when the pin sticks out it's under tension and then it's difficult to retract.
Another thing I've noticed is some of the black paint on the socket comes off after one or two uses--could a piece of that paint be getting stuck somewhere? Maybe it gets stuck in the rear preventing the flash from sliding completely into the socket resulting in the pin being slightly off-center.
FYI, my 540 fits in pretty smoothly--it's snug, but goes on and off easily and quickly. I've used it dozens of times.
Just some thoughts.
Bart
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Forum: Photographic Technique
05-15-2007, 11:08 PM
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When doing landscape and nature photography, I want to be in aperture priority. I know the aperture I want and I pick it. Quite often (especially in low light) I manually adjust the ISO downward several notches because the SR allows a lot of leeway. However, I often want to return quickly to auto ISO, so I can push the green button and it leaves the aperture to what I selected.
The problem with hyper-P mode for this situation is I have to hold down the ok-button while spinning the front knob to change ISO. And I have to also hold the ok-button while pressing the green button to auto-set the shutter speed and ISO w/o affecting aperture. In a lot of casual shooting situations, this is easy for me to do. However, in nature shooting, I routinely find myself crawling around in the dirt, or squatting sideways on river rocks, holding the camera at a funny angle relative to my body, and there's something about those positions that makes it very uncomfortable to push the ok button AND one other control at once.
Now, IMO, a DSLR is as much about comfort and fluency as anything else. It's unimportant that it's possible to get all the same behaviors in hyper-P mode as in Av mode. What important is how you get to those modes and I appreciate having even the arguable subtle choice of not having to hold the ok button when it's awkward (and when I know there's zero chance of me needing anything besides Av mode.)
Same story for shutter priority--the green button leaves the shutter speed alone w/o pressing the ok button.
Same story again for Sv mode, although I personally don't use that one very often lately.
I think it's pretty obvious that Manual and TAv modes will be needed for some extreme situations. My most common situation is in creative lighting situations with the remote flash where I sometimes need to adjust the relative strength of ambient lighting by more than 2EV.
There also seems to be a bug in P mode--it only lets me slow the shutter speed down. It's also very probable that many folks like to program P mode to behave as it does in other cameras--program shift and EV comp for the two dials. Astrophotography also requires M mode.
BTW, I use P-mode too. I can throw on my 540 flash, put the camera in P-mode and start mindlessly blasting away and the pictures just all turn out great--probably because the flash reduces contrast which is easy for the exposure program to always get right. I'm going to be shooting an outdoor event later this summer and I expect that P-mode will be what I mostly use--with and w/o flash.
Bart
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Forum: Pentax DSLR Discussion
05-04-2007, 10:41 PM
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One other thing--as far as I know, none of the current live-view DSLR's is able to auto-focus in that mode. I'm sure this easy-to-overcome limitation will change in the not-so-distance future as well.--and about that time DSLR's will be able to shoot video as well.
Bart
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Forum: Pentax DSLR Discussion
04-23-2007, 12:48 AM
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I bought my 540 from Tristate--got it about a week ago. I think that's about as good of a deal as there is (another $15-$20 for shipping.)
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Forum: Pentax DSLR Discussion
04-16-2007, 04:20 PM
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I've thought of this too. The main problem I thought of was the anti-aliasing filter which has already removed almost all of the extra information above Nyquist. Now if you cold somehow have a camera mode that also moves the AA filter out of the way, then you'd really have something.
In the meantime, it's a lot technically easier to simply double the focal length, take four adjacent photos and then stitch them together. Solves the AA filter problem as well. Downside is it's only good for landscapes, but that's the only time I ever want more resolution.
Bart
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Forum: Pentax DSLR Discussion
04-16-2007, 10:01 AM
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I leave it on by default and it easily provides stabilization for shutter speeds faster than 1/60s. Eg., at 200mm if I can't get a stable hand-holding position, I might need a shutter speed of 1/300s to get a reliably stable shot without SR. With SR, that drops to 1/50s or even slower.
However, when you are panning in a NON straight line (ie., following birds, bugs, or kids), you need to turn off the SR because, 1) the SR will try to counter your movements, 2) it'll hit the rails and you'll get vignetting because the edge of the sensor leaves the light circle. Even with fast shutter speeds (1/800s) I've had SR ruin a shot because I accidentally left it on during a panning action shot.
That's an interesting theory. I have seen various reviews that claim the lens IS is better, but only at long focal lengths (~200mm) and only by about 1/2 stop.
Besides the obvious reasons, the beauty of having it in the camera is if they come up with an improved version in the future (and you know they will), then you could upgrade your body and your whole lens collection gets updated with it. So your lenses don't get obsolete as quickly as they would with the IS in the lens.
Bart
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Forum: Pentax DSLR Discussion
04-15-2007, 05:52 PM
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That's interesting. Tapered lugs and location of lock tab are the same. Sigma did borrow an important aspect from Canon and that is the control pins are inside the cavity instead of in the interface surface. I think this might be why the Canon mount feels a little smoother when twisting lenses in and out.
If you ask me, they took the best from both.
Bart
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