|
Forum: General Photography
05-27-2021, 02:37 AM
|
| |
I've never really seen a camera bag that comes anywhere close to a decent hiking bag (with the exception of the Kata bumblebee, but that went out of production around the time I found out about it). So I use a Tenba BYOB (bring your own bag) insert into a Deuter hiking backpack. Not as great for quick accessibility as dedicated bags, but comfortable with good back venting. When hiking, I'd typically keep the camera loose on in the backpack on top of the BYOB for quick access, or only bring the camera with one lens.
Another advantage is that when your bag looks like an old hiking backpack, people won't assume there is valuable stuff inside of it.
|
|
Forum: Pentax K-3 III
05-21-2021, 12:08 PM
|
| |
That is very interesting! I had no idea!
|
|
Forum: Pentax K-3 III
05-19-2021, 12:25 AM
|
| |
Yes. Nobody expects the maths police.
Here we can assume from context that you are using the integers 1 and 3, which are defined with infinite precision. A vertical sensor size stated to be for example 15.5mm is not necessarily defined that precisely. Its likely not 15.50000000mm, but some value between 15.45 and 15.55mm. The pixel pitch stated earlier of 3.76um for example does not fit exactly in 15.5mm. But we have no way to know if that number is precise either.
Definitely. Apologies for that, I can't help it.
I agree with all of that. I was also one of those people stating that the sensor size is slightly different. Not 1.5 to 1.54 different though, the crop factor of the original K-3 was closer to 1.53.
However, I think my point is still valid, especially in cases where a lens has known focus breathing. To restate that point (at the risk of being somewhat obnoxious): you can apply a crop factor of 1.54, or maybe 1.5, but unless you know well how your lens behaves, and what its focal length is as a function of distance, its not that useful. The exact effective focal length will likely be different. But as long as you take the number with a grain of salt and don't expect your 100mm to become 'exactly' 154mm regardless of the circumstances, its fine.
|
|
Forum: Pentax K-3 III
05-19-2021, 12:08 AM
|
| |
It seems to me that differences in colour fidelity should always exist, but in many cases where the sharpness is limited by the optics rather than by the sensor, pixel shift shouldn't have much of an effect on sharpness. In those cases where the lens limits the sharpness, moire should also not show up.
|
|
Forum: Pentax K-3 III
05-18-2021, 11:20 PM
|
| |
Very good point. The aspect ratio isn't exactly the same when just dividing the provided sensor size, but this might very well be due to rounding the sensor size to the nearest .1mm. In that case we can probably use a somewhat exact crop ratio if we can find out more exact data for the sensor size, although I still think it doesnt pay to be too precise due to the other two points I raised above.
|
|
Forum: Pentax K-3 III
05-18-2021, 10:57 PM
|
| |
It is not strictly legal to derive a ratio with a higher precision than the numbers used to get it. Basically, given that the last significant digit in the focal lengths is entire millimeters we can assume it is rounded to the nearest millimeter. The ratio is then somewhere between 61.5/39.5 and 60.5 and 40.5, or between 1.494 and 1.557.
There are many reasons why being too precise does not make much sense (but just using for example 1.54 as a rule should be fine)
1) I think that crop factor only really makes sense if the aspect ratio of the sensor is kept exactly the same. They are different between full-frame, the earlier K-3s and the K-3 mark 3. We then have to choose if we want to divide the horizontal sensor size, the vertical size, or the area. That the aspect ratio matters can be seen from a though experiment: keep the area of the sensor the same, but go to an extreme aspect ratio, and think about what picture the same lens will get on such a sensor compared to a full frame sensor. Then you immediately see that crop factor does not make sense without indentical aspect ratio
2) Often the effective focal length of a lens depends on the shooting distance, which I think is called focus breathing. The difference in focal length when shooting at minimum distance and infinity can be pretty huge (I remember some anecdotal evidence of a 70-200mm zoom for which the '200mm' setting at minimum distance is actually 135mm. Some prime macro lenses are also known to have this problem). That means that in not-infitnity shooting conditions, the focal length can be much further off from the indicated value than doing the crop calculation with a factor 1.5 or 1.54. No use trying to be too precise.
3) Finally, with many lenses the focal length is not even exact at infinity, although this difference can be small. Eg, an 85mm lens might actually be 83mm, but marketed as 85mm because its a familiar number. While this difference is small, so is the difference between 1.5 and 1.54 crop factor.
|
|
Forum: Pentax K-3 III
05-17-2021, 02:20 AM
|
| |
Looking at the sensor size, the K-3 used to indeed be around 1.53x, but the new sensor is very slightly smaller (if the numbers from imaging-resource are precise), so now the crop factor is very slightly higher.
The crop factor is also not the same for the horizontal and vertical axis for either the K-3 or K-3 mark III btw, which makes determining an accurate crop factor a bit tricky.
|
|
Forum: Pentax News and Rumors
01-19-2021, 10:31 PM
|
| |
It being speculation, it does not explain anything with any type of certainty, but I think there might be something to it.
It seems to me that the D-FA100mm has approximately 270 degrees of focus, but nearly all of that is within 1m. The distances within 1m-infinity are all covered within approximately 15 degrees of focus throw. If the lens for example checks for focus at each X degrees of screw drive rotation, this means it does 17 times more checks between 30cm and 1m than between 1m and infinity. Of course, I hope something more intelligent is programmed in, but I don't know if it is.
|
|
Forum: Pentax News and Rumors
01-19-2021, 07:30 PM
|
| |
My initial guess, given the above, is that the problem is just very difficult. Assuming the above explanation about the AF is correct, the camera would be looking for a region in the picture with high local contrast given by peaks in the Fourier spectrum at relatively high frequencies. If we have a 3D macro subject, that presents 2 problems that are trickier for macro than many other shooting situations:
1) When somewhat out of focus, if the subject is 3D, there will still be parts of the subject in focus. This problem also exists in general shooting situations, and has mostly to do with the camera having to know where to look for max focus.
2) The amount and location of the obtained contrast shifts very dramatically even with small shifts in the focal plane. This might cause problems in macro situations. The autofocusing is (I think?) done with the lens wide open, so the DOF is very small especially when focusing near 1:1 magnification. When the focus is hunting, the camera is likely focusing at some subset of focus planes, and when finding something will then fine-tune. A compromise has then to be made between the lens being able to scan its entire focal range in a reasonable time (going from 1:1 macro to infinity in a limited number of steps) and its ability to find the correct focus every single time. It might be that an algorithm that would cause it to check for focus by stepping less than 1DOF (which would be required to obtain focus every time) would be prohibitively slow. If the step is larger than 1DOF, missing the focal point by running over it becomes somewhat likely.
After finding an initial somewhat sharp region, auto-focus fine tuning with smaller focus shifts should in principle not be problematic.
This, of course, is all completely speculative.
|
|
Forum: Pentax News and Rumors
11-15-2020, 10:47 PM
|
| |
I also clicked it, really nice pictures!
I'll attempt to get the lens once I can figure out where to get it in Japan.
|
|
Forum: Lens Clubs
04-09-2020, 11:04 PM
|
| |
Well, I have the gear, but not the skill to do either the camera or lens justice. I am enjoying it though, part of the reason I got it is its close up ability, and it does not disappoint.
I shot does image of a rock on one of my first outings with it (it being the zeiss 25mm/2.8)
 [url=https://flic.kr/p/2iGHqeW]
|
|
Forum: Pentax News and Rumors
03-25-2020, 05:01 AM
|
| |
This is nothing new right? I'd argue that all lenses without aperture ring could already not be used on a lot of older cameras. Lenses are not always backwards compatible, but cameras are, and pentax keeps doing that. That way we can keep using our (sometimes large) collection of pentax glass, while occasionally updating the camera. Updating a camera once every very many years is a much more financially feasible solution to users than having to change all lenses by changing the mount completely.
|
|
Forum: Lens Clubs
03-14-2020, 06:33 AM
|
| |
Hello all, this is not strictly ZK news (but rather ZS news). Fujiya in Japan (a shop in Nakano, Tokyo) is apparently selling off some of their stock. They are currently selling new Zeiss distagon 25/2.8 in ZS mount (M42) including a K&F mount converter of your choice for just under 50000 yen, or 463USD or 416 Euro (today they were out of converters though, but I took that as an excuse to buy the pentax genuine converter instead). As far as I can tell, that is far under even used prices.They won't sell internationally, so if you are not in Japan, you'd have to use one of these intermediate companies to order and ship for you. Maybe it is still worth it? In any case, I'm quite excited to be joining the pentax-zeiss owner club!
|
|
Forum: Pentax News and Rumors
03-11-2020, 05:48 AM
|
| |
Some shops in Japan still carry the K-1. Fujiya in Nakano (tokyo) interestingly has it for nearly the same price as the special edition KP (~133.000 yen). The K-1 mark 2 is about 211k yen in the same shop.
|
|
Forum: Pentax News and Rumors
01-10-2020, 03:09 AM
|
| |
Why do you keep insisting it is realistic for pentax to release a camera with tech pentax currently doesn't have (fast framerate, high buffer, good AF which are all required to be competitive in the 24MP FF market) at a cheaper price than competitors who released such cameras that did already have that tech?
Pentax was able to release a good D810 competitor because the existing strengths of pentax (high IQ, tricks with the IS system to get extra detail and colour fidelity) could be used, and some things specific things (pixelshift, astrotracer) could be ported from other models (with some extra engineering of course). Pentax has never been a top contender in speed and AF in the digital world as far as I remember, so what makes you think they can suddenly bypass Nikon, Sony and Canon who have been investing research into these areas continuously? And then somehow come out with a cheaper product?
To me it seems like continuing to play to the traditional pentax strengths by putting out a D850 competitor at a lower-than-D850 price seems more plausible. That said, I'd be quite interested in a 24MP FF. I don't care much about the speed or AF though, and I think it would be hard for pentax to compete in the 24MP FF market.
I guess the new APSC might give a bit of a hint as to what will happen to the next FF. The new tech in that camera will likely end up in the next FF to some extent.
|
|
Forum: Pentax News and Rumors
01-07-2020, 09:38 PM
|
| |
If 'legitimate rhetoric technique' means it can win a debate in some cases (i.e., its an effective technique) than so are most fallacies.
Whether that definition works or not, both ad hominem and fallacies, regardless of efficiency are bad form, and do indeed take away from your own credibility even if the rest of your arguments are convincing.
(To go ad absurdum: if one wants to convince another person to do something they don't want to do, threats of violence or actual violence are an extremely effective technique. That doesnt mean they should be employed)
|
|
Forum: Pentax News and Rumors
12-18-2019, 04:49 AM
|
| |
Thanks, that makes a lot of sense, I didn't think about objects our of the focus plane, but it matters.
When I first started stacking, I somehow had not thought about the fact that the object in focus keeps the same size as you shift the camera. This makes objects looks slightly unreal. Especially in the case you shoot things with regular features on a flat plane. With a normal picture (or a stack changing the focus point) you expect to see some perspective, but with stacking shifting the camera/lens (or object) the perspective disappears, so you get some type of orthographic projection instead. Unfortunately a telecentric lens won't change that. With insects, this lack of perspective is not clear as insects are not mostly parallel straight lines.
|
|
Forum: Pentax News and Rumors
12-12-2019, 12:52 AM
|
| |
Yes, its always a lot easier to build a device with new technology you have not developed and have no in-house experience with than it is to improve existing technology to get better performance. Much easier. For sure. Its like printing money.
|
|
Forum: Pentax News and Rumors
12-11-2019, 03:58 AM
|
| |
Lets take that ad absurdum. Why make photographs at all? Using photoshop, and perhaps some other software such as blender, and infinite skill and time, one can produce any picture at all without having to use a camera. Why waste money on camera and lenses? Just make it from scratch.
(In case it was unclear, I agree the lensbaby's have a place, and disagree with the people that disregard it because hypothetically it can be done in post. That said, I dont have a lensbaby yet. The Sol looks like a more convenient version of my DIY tiltshift though, so I might consider it)
|
|
Forum: Pentax Forums Giveaways
12-11-2019, 12:30 AM
|
| |
| |
|
Forum: Pentax News and Rumors
12-11-2019, 12:29 AM
|
| |
I have a different opinion on this one. I think the LX is one of the best looking cameras ever made, and it would take real talent to make it ugly. But they definitely managed (and then some). What an abomination. Now the titanium version on the other hand...
|
|
Forum: Pentax News and Rumors
12-11-2019, 12:22 AM
|
| |
They did specifically mention astrotracer, and also specifically mentioned that most of the features were present on the previous flagship.
The quotes from the DPR page about these two specific points:
'Backlit controls and neat features like 'Astrotracer' make it attractive to nocturnal photographers, too.'
'The K-1 was packed with all the special features that Pentax users had come to appreciate in the company's APS-C DSLRs'
|
|
Forum: Pentax News and Rumors
12-09-2019, 01:01 AM
|
| |
I'd also be very interested in seeing your rig. I've only managed to get up to 6.5x so far, having a setup that extends from mild magnification all the way to 16x sounds amazing!
|
|
Forum: Pentax News and Rumors
12-06-2019, 12:50 AM
|
| |
Laowa and Mitakon both have a few lenses that do more than 1:1 magnification, and both have gotten good reviews, although its not clear if they are really better than connecting lenses in reverse.
However I'd say these lenses do not directly compete. The laowa is even more niche and specialistic than this one, only starting at 2:1 magnification and needing very close working distance.
I was wondering if the near-telecentric design would help for my specific applications, but thinking about it more, I think it probably doesnt. Unless I'm mistaken, in most cases people fix the magnification and focus distance, and then move the camera (or object) for focus stacking. I think in such a case you get a 'telecentric' result in any case. I'd be happy to be wrong about this though.
|
|
Forum: Pentax News and Rumors
12-05-2019, 03:46 AM
|
| |
And part four:
You Tube
|
src="https://www.youtube.com/embed/TmtnmO-KGUw?controls=1" allowfullscreen>
|
|
