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Forum: Pentax News and Rumors 04-25-2019, 09:39 PM  
The Pentax K1 III might be close
Posted By xandos
Replies: 332
Views: 29,520
A true lower ISO would require that either there is a lower input, or that the sensor has a capability of detecting lower signals than it currently does.


Here is how I understand digital cameras, please tell me where I go wrong: It seems to me that the current base ISO is the 'full' sensitivity of the sensor, ie, it records what it detects in its full single-pixel dynamic range (in case of an 8-bit sensor (for the sake of simplicity), the camera settings will be such that the brightest parts of the scene will register at near-max values (256). For an 8-bit sensor, the lowest values are ~1, and the dynamic range is basically given by this: the contrast between the highest and lowest value.
Now if we increase the ISO, we collect less light/lower values by changing the camera settings, and adjust by amplifying the signal. In doing so, we also amplify noise. Besides, if we use the full sensor range (0-256), we have 256-intensity steps per colour, but if we collect less light (lets say, for example, 128 steps) and amplify by a factor 2 to get back to the same values, we have less information, because we basically only have the even numbers from 0-256. We will have much less nuance in the colours. I don't entirely believe that this explanation is 100% correct, so if someone knows, please tell me.

If we want to do an attenuation step, we have a similar problem. For ISO 50, if our base or native iso of the sensor is 100, we'd have to set the camera up to massively overexpose and then de-amplify all sensor values. We run into a few problems: the sensor clips at maximum value of 256, so everything above is lost. So after de-amplification, if it was for example by a factor 2, there will be no brightnesses in the raw values above 128. Basically we lose the right part of the histogram. For the other values, we have rounding problems: for a deamplification of factor 2, each 2 histogram bins in the original is collapsed into a single bin post deamplification. So I think we should get very poor / no highlight recovery at all, and a hit in dynamic range.
Forum: Pentax News and Rumors 04-25-2019, 06:50 AM  
The Pentax K1 III might be close
Posted By xandos
Replies: 332
Views: 29,520
Can you explain? To me it seems like it would be very difficult to do so, except maybe by putting in a switchable ND filter (which still doesnt seem trivial). Sure, they could implement a amplification step with gain lower than 1, (compared to the usual amplification with gain >1 for when going to higher ISOs) but the dynamic range would take a huge hit. Am I missing something?
Forum: Pentax News and Rumors 04-11-2019, 10:39 PM  
The Pentax K1 III might be close
Posted By xandos
Replies: 332
Views: 29,520
Wouldnt it be best to be in the situation where writing to the card is as fast as / faster than your maximum shooting speed?
Forum: Pentax News and Rumors 04-11-2019, 07:48 AM  
My Report from CP+ 2019
Posted By xandos
Replies: 238
Views: 17,389
Doesnt the accelerator chip sit between the sensor and the main processor? I doubt there is anything that can be done in firmware if that is the case. I think in order to make the accelerator switchable, if Ricoh did not intend to do so right from the beginning, probably the entire board needs to be redesigned.
Forum: Pentax Camera and Field Accessories 04-09-2019, 10:45 PM  
Cheap kit to get started with Macro photography
Posted By xandos
Replies: 37
Views: 1,499
Another thing you can do: in the 'macro by any means necessary' club you can see how other people are doing macro with macro lenses. You'll find results of most of the methods mentioned above there.
Forum: Pentax Camera and Field Accessories 04-08-2019, 11:29 PM  
Cheap kit to get started with Macro photography
Posted By xandos
Replies: 37
Views: 1,499
If you have a few old manual lenses, I recommend getting the reverse coupling adapter that some people also recommended above. I use it without extension tubes with my pentax-M 28, 40 and 50mm lenses, and get results I'm very happy with. You can always add extension tubes later to increase magnification, but a reversed 28mm already gives you more than 1:1. If you were to use extension tubes with reversed lenses, they obviously can be very simple: there won't be electrical contact anyway. Such an adapter or simple extension tubes are available online for about $10.

I have the D-FA macro which is fantastic. I used the reverse adapter before I could afford it, but still use it now and then for a very compact macro setup with more magnification than the macro lens.
Forum: Pentax K-1 04-05-2019, 12:40 AM  
Weather sealing comparison: Interesting video
Posted By xandos
Replies: 8
Views: 1,123
Very interesting. I only got into photography much later (about ten years ago), and for me the reason I started with pentax was low-light capability and small cameras (I started with the k-x, which at the time was good in both ways). The reason I stayed and will stay in the foreseeable future, is that I really like the quirky stuff pentax does: IBIS, astrotracer, AA simulator, pixelshift. The low-light capability of the K-5 for astrophotography is still competitive even now. Native compatibility with old manual small metal lenses and weathersealing are a great pro too.

I might not be the typical customer, but for me the fact that pentax lags in AF and video is way less important than the IQ and IBIS-related tricks they implement before anyone else does. If pentax would not be doing these type of innovations nobody else is looking at, and instead make Nikon-like AF, they would lose customers like me. What I would like, though, is a smaller K-1. But I guess that is at least very very difficult, if not impossible.


To get back on topic: I like that this guy is doing pentax videos, but I find it really hard to stomach his style somehow. I don't know what it is. I have no complaints about the contents of the video. Testing the weather sealing of each camera would be nice, but would probably end up being way too expensive for a small channel, we can't really ask for that.
Forum: Pentax K-1 04-04-2019, 03:30 AM  
Weather sealing comparison: Interesting video
Posted By xandos
Replies: 8
Views: 1,123
Which generation do you think pentax lost?
Forum: Lens Clubs 04-03-2019, 10:04 PM  
*Macro* lens club
Posted By xandos
Replies: 3,378
Views: 448,529
Some sakura blossoms, with the D-FA 100mm WR on the K-1, wide open


sakura
Forum: Winners' Showcase 04-01-2019, 11:52 PM  
March, 2019 Third Place: Autumnal Mists
Posted By xandos
Replies: 45
Views: 1,005
fantastic picture
Forum: Monthly Photo Contests 04-01-2019, 11:51 PM  
hi
Posted By xandos
Replies: 50
Views: 752
I would like to nominate this photo
Forum: Lens Clubs 03-15-2019, 02:23 AM  
Macro by any means necessary club
Posted By xandos
Replies: 512
Views: 100,329
I can't say I agree with that logic. Diffraction and light wavelength limits what we can resolve eventually, but I can take a camera with a pixel pitch of 50um, hook it up to a microscope and resolve details way beyond 50um. That is what the magnification is for. My setup should give me a magnification factor of about 7 (more with the 21mm), so I'm not limited by pixel pitch yet. And if I were, I could still increase the magnification factor of the setup. In other words, pixel pitch doesnt set a limit on resolving power if you play with optics.
Forum: Lens Clubs 03-14-2019, 07:58 PM  
Macro by any means necessary club
Posted By xandos
Replies: 512
Views: 100,329
Thanks for the very quick replies! I avoided getting the 21LTD for a long time for its lack of aperture ring (and incompatibility with FF for when I cave and get a K-1), but I ended up putting in a lowball bid and getting it for way under the price I could get a pentax-M 20mm/4 for, I guess I cannot complain! Although the lens rattles, something is loose inside. Very disconcerting. But it shoots just fine.

I tried the thing with the DoF preview while dismounting the lens. That definitely does not work for me. I'll look into the fotodiox mount, that would probably do the trick! I've been trying to hold the aperture lever in place by hand, but its tricky. I use the 21mm reverse/mounted on a 200mm, so I can have no vibrations at all, and exposure times are often about a second.

I got pretty decent results recently with a 28mm/200mm. I am still hesitating if I can post them here, they are work-related designs, so its a bit iffy. But I can definitely resolve structures smaller than 5um, so I am pretty happy. The reversed 21mm instead of the 28 should give me a decent extra bump in magnification, if its similarly sharp. The M28/3.5 is quite good at this kind of stuff.
Forum: Lens Clubs 03-14-2019, 12:36 AM  
Macro by any means necessary club
Posted By xandos
Replies: 512
Views: 100,329
Can anyone tell me how to use newer lenses in reverse? I recently got a 21mm LTD which I'd like to use with my 200mm instead of my pentax-M 28mm/3.5 (that combination works great btw), but the lack of apperture ring doesnt help. Does anyone know any tricks to get the 21mm to keep a certain aperture when used in reverse?
Forum: Monthly Photo Contests 12-09-2018, 11:32 PM  
Serenity
Posted By xandos
Replies: 40
Views: 677
I would like to nominate this photo
Forum: Pentax News and Rumors 11-14-2018, 03:53 PM  
K3ii replacement
Posted By xandos
Replies: 2,451
Views: 181,048
Well, if you optimize it for efficiency (switch off back LCD, use manual lenses, shoot in reduced resolution JPEG-only) you can get far beyond 1500 shots. I used the K-5 as a timelapse device for a while and could shoot about 4000 pictures (give or take 1000) before having to switch the battery. This was of course within a single day, and under very light circumstances for the K-5. But its battery life is really fantastic, I've never had to switch a battery within 600 pictures under any circumstances (I never used built-in flash though, that might matter).
Forum: Pentax News and Rumors 10-08-2018, 07:33 AM  
K3ii replacement
Posted By xandos
Replies: 2,451
Views: 181,048
Maybe I don't count as a 'photographer', but handheld night photography is certainly something I do*. Besides. for non-handheld photography, dark AF would be convenient for tripod work too. That said, most of my bright lenses are MF anyway.

*I am a single data point, so this doesnt contribute much to the topic, but neither does your rather questionable statement that handheld night photography is not something photographers do a lot.
Forum: Monthly Photo Contests 10-07-2018, 08:06 AM  
Moondance
Posted By xandos
Replies: 35
Views: 582
I would like to nominate this photo
Forum: Pentax News and Rumors 10-05-2018, 09:41 AM  
K3ii replacement
Posted By xandos
Replies: 2,451
Views: 181,048
Well, different people have different opinions. I am fine with the weight of the cameras, I think really good build quality and robustness comes with some weight, and a very rigid frame (magnesium and steel are good, carbon fibre and plastics can be strong but are not as rigid) is probably necessary for the IBIS to function.
On the other hand, I'd really like the cameras to be smaller, closer to film-era sizes, which would allow me to carry more things in my backpack. The compactness of Pentax cameras compared to other brands was one of the reasons (together with low-light capability) that made me decide on pentax when I bought my first 'serious' camera.
Forum: Lens Clubs 09-26-2018, 09:51 AM  
Macro by any means necessary club
Posted By xandos
Replies: 512
Views: 100,329
Great stuff! I especially like the first two!
Forum: Pentax News and Rumors 09-15-2018, 11:26 AM  
K3ii replacement
Posted By xandos
Replies: 2,451
Views: 181,048
At the risk at nitpicking or even being wrong: before aluminium is cut it will already be covered by a thin oxide layer. A cut will expose 'bare' aluminium that will then oxidize. The good thing is that the type of oxide aluminium forms is only on the surface, and will not penetrate and degrade the material below it. In that sense its quite different from iron oxidizing. I do think that the ease of machining and weight also play an important role in the decision to use it for lenses. Otherwise, stainless steel could be a good alternative, which would be less damage-prone. I have no clue if other things such as thermal expansion coefficients etc. come into play when making these decisions.
Forum: Pentax News and Rumors 09-04-2018, 09:55 AM  
K3ii replacement
Posted By xandos
Replies: 2,451
Views: 181,048
Earlier on in the thread I argued that a digital camera has to be deeper than an old film camera by at least the space required for the rear screen and the IBIS mechanism. So a true film-like camera size is not doable without giving up on those features. I'd be very happy if we get closer to it, but from the perception of the KP it seems people are not willing to compromise on other necessary changes such as a smaller battery.
Forum: Pentax News and Rumors 09-04-2018, 09:05 AM  
K3ii replacement
Posted By xandos
Replies: 2,451
Views: 181,048
I don't think it would help all that much. The K-mount comes with a set distance between the mount flange and the sensor. The extra space digital cameras need compared to analog cameras (assuming we retain the K mount) is what is around/behind the sensor (IBIS motors and logic boards) and the screen. These are the same for DSLRs and MILCs. A mirrorless K-mount camera would always have a huge amount of wasted space between the sensor and the flange.
Forum: Pentax News and Rumors 09-02-2018, 12:36 PM  
K3ii replacement
Posted By xandos
Replies: 2,451
Views: 181,048
I think there are two things that prevents the possibility of an LX-shaped digital camera:
- IBIS
- rear screen
These two increase the minimum depth needed to build a DSLR over a film camera. Arguably the battery does too, but that can be shifted around to some degree.

I really want an LX-shaped new digital pentax though. But not without IBIS.
Forum: Sold Items 08-02-2018, 02:46 PM  
For Sale - Sold: Pentax F* 300mm F4.5 lens
Posted By xandos
Replies: 24
Views: 1,959
Wow, wish I'd seen this in time
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