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Forum: Pentax K-1 07-22-2016, 08:55 AM  
K1 astrotracer with ultrawide lens Question
Posted By lister6520
Replies: 15
Views: 2,170
It is not just a matter of rectilinear or not. With linear sensor shift it is never possible to accurately track the angular motion of the subject over the whole sensor. The issue is not only with Astrotracer but even with shake reduction. The only reason we don't worry about it with shake reduction is that with wide angle lenses shake is not usually much of an issue anyway.

It can be geometrically shown that shifting the sensor can never fully compensate for an angularly moving target regardless of how perfect the lens is. Briefly explained, if a target at the centre of the image moves by x degrees it will correspond to a linear movement of y pixels on the sensor. However a target towards the edge of the image moving the same x degrees will shift more than y pixels on the sensor. (The amount is determined by the trigonometric 'tangent' function)

The further (in degrees) the target is from the lens axis the larger will be the linear shift (in terms of pixels or microns) on the sensor for a given focal length. The longer the focal length (and hence the narrower the field of view) the less will be this difference, so for instance at 300mm there is hardly any difference between the centre and the edges of the image.

This all applies to a theoretically perfect rectilinear lens - it is a function of physics and geometry and not imperfections in the lens.

Any lens distortions and imperfections will of course add onto this problem as well.


To get good very long exposures with wide angle lenses you will need to limit the individual exposure times and re-aim the camera before each image of the stack. The re-aiming doesn;t need to be extremely accurate but if you can get an easy to see star at the centre of the view finder it makes it a lot easier.




PS: now only after posting I realise that there were more posts after the one I was responding to. My apolgies for repeating a lot of what has already been said and explained in those subsequent posts
Forum: Pentax K-1 07-21-2016, 01:46 PM  
An Open Letter to Pentax: K-1 Infinity Focus Problems
Posted By lister6520
Replies: 35
Views: 4,077
I think you have misunderstood the problem being reported by rcolman. The issue here is not how to find the focus but that when fitted on his K1 the lens reaches the end stop, at or beyond the infinity mark even before it has actually reached infinity focus. In other words it is mechanically impossible to focus the lens at infinity no matter how hard you try.
No bright star in live view is going to help with that. It would need something more like a large monkey wrench to grab the focus ring and force it to turn a few degrees further.
Forum: Pentax K-1 07-21-2016, 01:07 PM  
An Open Letter to Pentax: K-1 Infinity Focus Problems
Posted By lister6520
Replies: 35
Views: 4,077
I think this should be considered a manufacturing defect and the dealer should give you a new and functioning replacement. If it cannot focus at infinity it is broken and I don't think they can argue against that.
Forum: Flashes, Lighting, and Studio 07-21-2016, 09:05 AM  
Bounce flash underexposure in P-TTL
Posted By lister6520
Replies: 25
Views: 1,475
One thing to watch out for - there is some odd logic in the software which changes the exposure calculation when it detects the flash head is not in the straight ahead direction (there is some microswitch or something in the flash head to detect this). I'm not quite sure what that logic is meant to achieve but as far as I can tell most of the time it seems to be counterproductive. I guess they tried to use it to tweak the exposure some way to take into account the different type of illumination but got the math wrong.

I've had the problem often with a K-r and K-30 using a Metz flash.

A simple experiment to do : instead of tilting the head to bounce the light instead leave it pointing forward and use a vanity mirror or something similar at 45 to direct the light upwards in the direction you would have tilted the head. This achieves the same effect as tilting the head but fools the camera into thinking it is direct illumination so it does not modify the calculation. I think I had posted the results in this forum somewhere but haven;t managed to find it.

I had experimented quite a bit with this and got good exposure in all situations where tilting up the head got me underexposure. I'm not sure if they've fixed this problem with new firmwares or on the K-3, or if they even consider it a problem. I had tried this some years ago and haven't used flash much since then.
Forum: Pentax K-1 07-21-2016, 08:30 AM  
An Open Letter to Pentax: K-1 Infinity Focus Problems
Posted By lister6520
Replies: 35
Views: 4,077
This sounds quite odd to me. I have three Pentax DSLRs and all but one of the 'digital' lenses I have can focus slightly beyond infinty. I'm wondering whether some bright spark at Pentax decided to bring back the infinity focus at the end stop that some people seem to miss a lot. Except that such a thing is not practically possible with a DSLR. It wasn't either with film actually except that we were less demanding then it seems.

BTW the one exception is a Tamron 10-24mm wide zoom which I had dropped right after unpacking from the box :o which may possibly have some bearing on how it focuses. I have some old k-mount lenses as well but I haven't really checked how they focus at infinity.
Forum: Pentax K-1 02-26-2016, 11:08 AM  
If You Haven't Already Seen This. ...
Posted By lister6520
Replies: 16
Views: 2,275
Sometimes I think the only reason they took so long to put in an articulated screen is that they wanted to be absolutely sure it lived up to the same expectations of ruggedness as the rest of the camera. Seems the time spent was well worth it.
Forum: Pentax K-1 02-26-2016, 11:04 AM  
High speed sync
Posted By lister6520
Replies: 43
Views: 3,611
Maybe has already been mentioned, but if it can do 1/200 in full frame it should be able to do 1/300 in crop mode.
It is something very easily implemented in the camera firmware with no changes to the flash itself but does anyone know if they actually put in that feature?

Also, is there any mention of overriding the 'safety feature' that protects us from the perils of triggering a flash with a shutter speed higher than the sync speed?
Forum: Pentax DSLR Discussion 12-22-2015, 01:14 PM  
Turn off shutter sound?
Posted By lister6520
Replies: 42
Views: 5,584
The lens also seems to me to make a big difference in the noise. My K-3 is significantly louder with a Tamron 10-24 than it is with the Pentaxk 18-135 WR. Maybe the weather sealing also muffles the sound of the shutter.
Forum: Pentax DSLR Discussion 12-22-2015, 12:56 PM  
Pentax k3 bulb mode problem
Posted By lister6520
Replies: 8
Views: 1,037
How do you know it is 1/25 s ? Do you see it in the EXIF or by judging from the brightness of the image?

Try with the lower manual speeds such as 1 or 4 seconds. Do you get the correct exposure then or still the 1/25?

What I suspect is a faulty latch for the second curtain. If so the slow manual speeds will also not work. If the slow manual speeds work correctly then it is almost certainly a firmware problem and might be fixed with a factory reset and perhaps a firmware upgrade if you are not already on the latest.
Forum: Pentax K-3 11-30-2015, 02:17 PM  
K-3 with Metz 58 AF-2
Posted By lister6520
Replies: 9
Views: 2,800
I have a 58 AF-2 but the sensor is not there but on the side just below where you show it.

What were they thinking when they hid it under the head in your version? Is mine more recent and maybe someone realised what a silly idea that was?

I have used wireless at times with K-r, K-30 and also K-3 and it's always worked fine and also seems very sensitive.

Forum: Pentax K-3 06-07-2015, 04:35 AM  
Flash lag fixed / FW 1.21
Posted By lister6520
Replies: 47
Views: 5,355
Didn't work for me

First image is P-TTL with 1.02
Second is manual with 1.21
Third image is P-TTL with 1.21

No discernible difference between 1.02 and 1.21 in terms of lag but huge difference between manual and P-TTL regardless of firmware version. Still way too slow in P-TTL to capture 'spur of the moment' shots, which is when I need P-TTL most.


Not sure what's happening with the exposure probably nothing to do with the firmware upgrade - possibly inadvertently different orientation of the flash head before and after the update.

In the meantime I also did a little test shooting video of me pressing the shutter button. In manual the flash lights either in the same frame showing my finger contacting the button or at latest the next one. In P-TTL I get about 4 to 7 frames between my finger hitting the shutter and the pre-flash illuminating. Then there are one or two further frames before the main flash illuminates. I shot the video with VGA resolution with a Q10, but I don't know what frame rate that corresponds to.

Sorry for the double post - I inadvertently posted in the old thread.

Read more at: https://www.pentaxforums.com/forums/172-pentax-k-3/296958-pentax-k3ii-has-shu...#ixzz3cNIZQCCa
Forum: Pentax K-3 06-07-2015, 04:16 AM  
Pentax k3II has the shutter lag problem wtih external flash
Posted By lister6520
Replies: 24
Views: 4,300
Didn't work for me :(

First image is P-TTL with 1.02
Second is manual with 1.21
Third image is P-TTL with 1.21

No discernible difference between 1.02 and 1.21 in terms of lag but huge difference between manual and P-TTL regardless of firmware version. Still way too slow in P-TTL to capture 'spur of the moment' shots, which is when I need P-TTL most.



Not sure what's happening with the exposure probably nothing to do with the firmware upgrade - possibly inadvertently different orientation of the flash head before and after the update.
Forum: Pentax K-3 06-05-2015, 01:02 PM  
Comparison K-3 II vs Nikon D810 and Pentax 645Z by imaging Resource
Posted By lister6520
Replies: 22
Views: 4,361
Regular shooting means different things for different people. The two types of subject I can think of that will benefit most are macro and architecture.

Of course it would always be better to use a 645Z if you can afford it and don;t mind carrying the weight but even for occasional use having a better resolution for some of your shots is always better than having it for none.
Forum: Pentax K-3 06-05-2015, 12:30 PM  
Pentax k3II has the shutter lag problem wtih external flash
Posted By lister6520
Replies: 24
Views: 4,300
The daft thing about the lag is that it is before the camera does anything at all. I could possibly understand if it does a preflash immediately then spent some time analysing the image of the preflash captured by the 86k sensor but it is not so.
You press the shutter, nothing detectable at all happens for a full 200mS or so then the preflash then almost immediately the mirror lifts, shutter opens and main flash fires. I had suspected it might be due to slow and/or inefficient communication between the flash and the camera but then I actually monitored the connections and found that there is no signal at all exchanged between the camera and flash in those first 200mS after pressing the shutter button, then after the delay everything happens in very quick succession practically as fast as mechanical limitations of the mirror, iris and shutter allow.
Forum: Pentax Full Frame 05-07-2015, 12:48 PM  
The Ultimate Full Frame Camera...
Posted By lister6520
Replies: 12
Views: 1,745
I don't think it likely thatframe rate is constrained mainly by the readout rate but by the mechanical limitations of the shutter and the possibly the mirror. With a FF there is much more mass to move and over a longer distance.

One may think that keeping the mirror up while shooting would therefore help but it would then make it impossible to see what you're shooting and also to track focus. However even so it is likely that the single action that takes longest is reloading the shutter for the next shot.

With regards the sensor readout it shouldn't really be an issue. To take an extreme example shooting 25 images per second at 100 megapixel per image image would require a 40Gbps transfer rate. It may look like a lot when thinking of a serial transfer such as an internet connection over fibre optic, but for a parralell transfer directly from sensor to ram over, say, a 256 bit parallel bus it goes down to just 155Mbps per line, quite easily achievable. 256 bit buses are also easily implemented for the short path between the sensor and the RAM so I would see the only moderately 'difficult' part would be having enough ADCs running in parallel on the sensor chip.

There is of course the issue of how much buffer RAM one can afford to put in the camera. In the example I mention you would need 5 gigabytes for every second of buffer capacity.

In any case even so, if the rate was not limited by the mechanical constraints it might still be useful to have even just two seconds of buffer at 25 FPS which would need ten Gs of memory.
Forum: Pentax DSLR Discussion 11-05-2014, 10:42 AM  
Auto-focus issues
Posted By lister6520
Replies: 8
Views: 774
I once had very similar symptoms with a K-r. In the end it turned out to be dirt, lots of it, on the AF optics at the bottom of the mirror box. Two of the focus points still worked properly (if manually selected) but the rest were all very erratic, including unfortunately the centre one.

I think the same can be caused by dirt on the mirror itself - it is actually partially transparent and light goes through it down to the focusing optics so any dirt or scratches on it can cause problems.
Forum: Pentax DSLR Discussion 08-16-2014, 01:44 AM  
Indecisive and sad
Posted By lister6520
Replies: 37
Views: 2,907
If I were in that situation I would definitely go for the K-3 without hesitation.

I upgraded from a K-30 to the K-3 about a year ago and I never regretted it.

I still have the K-30 and use it as a second camera. As far as I know the K-30 and the K-50 are exactly the same thing except for the external visual appearance.

I don't think the mirror flop issue is anywhere near as common as is is made to seem. Whatever you buy there is always the chance of it having some fault and if you buy something else instead of the K-3 I don't think it would be any less likely that you may buy a faulty camera.
Forum: Pentax K-3 07-30-2014, 12:42 PM  
K3 - two questions important to my choice to buy
Posted By lister6520
Replies: 29
Views: 4,434
Regarding the fitting of the mirror lens, if it is of any help I have a Samyang 800mm and it fits the K-3 with plenty of room to spare:


Forum: Pentax K-3 07-30-2014, 12:31 PM  
why I won't buy a k3 (Warning: Satire Thread)
Posted By lister6520
Replies: 42,069
Views: 1,448,538
I shall be returning my K-3 for a full refund. They must have sold me a fake.

I've had a similar experience with a Land Rover, not the lack of a flapping mirror though, but that it never breaks down as they are meant to do all the time. I have not succeeded in getting a refund or even a genuine replacement for that either though.
Forum: Pentax K-3 07-30-2014, 12:25 PM  
Weather sealing is nothing
Posted By lister6520
Replies: 112
Views: 10,299
I don't think it likely to be a matter of weak design but more likely the occasional manufacturing defect resulting in some seal which doesn't do its job properly. Manufacturing defects are something that can only be minimized but never eliminated completely. What perhaps should be different is the response from Pentax. I think it would be much better for everyone, and also the Pentax name, if they just admitted to the existence of the occasional manufacturing defect that slipped past QC and repaired that,

I have two weather sealed Petaxes, the K-30 and K-3. The K-30 has had its fair share of drenchings and I even rinse it thouroughly after using it in heavy sea spray and never had any issues. If there had been some systemic design fault I'm sure it would have caused me problems at some time or other but it never did. There are some things I think they could design better but it is by no means poorly designed.

The K-3 has had some experience with water but not nearly as much as the K-3. No problems at all to date
Forum: Pentax K-3 07-28-2014, 12:14 PM  
4K timelapse "bug"
Posted By lister6520
Replies: 13
Views: 1,366
Good that you mentioned that - I have been puzzled by the Q-10's timelapse video which gives a video which shows up as 24fps in the file info but looks more like 5fps. I only used it a couple of times and gave up, but I was more thinking that it was something I was doing wrong.
Forum: Pentax K-3 05-16-2014, 08:47 AM  
K-3 burst speed
Posted By lister6520
Replies: 5
Views: 1,204
What shutter speed are you using? Unless you are using fast shutter speeds the frame rate will necessarily be lower. I have consistently got between 8.5 and 8.7 at 1/500s.

The battery type and charge can also cause a significant reduction. I don't know the extent of the effect except for a perceived significant reduction when using a third party LiIon battery. I was using a new genuine Pentax battery for the test. NiMH batteries in the grip would probably also be slower than the LiIon battery, due to the higher internal resistance but I am unable to test that as I don't have a battery grip.

I used audio recordings to measure the rate.
Forum: Pentax K-3 05-11-2014, 02:04 PM  
ISO in video mode
Posted By lister6520
Replies: 4
Views: 812
Note though that in video mode it will only go up to ISO 3200, I'm not quite sure why.
Forum: Pentax K-3 05-07-2014, 09:49 AM  
Pentax Flucard O-CF1 firmware update wishlist
Posted By lister6520
Replies: 28
Views: 4,492
Two things I see as very important to make it more useable for me

First, to have it act as a WiFi client rather than an access point. In other words it would connect to an existing network rather than create its own. Among other things, the way it works currently is very cumbersome because one has to disconnect the PC / laptop / tablet / smartphone from the internet and everything else to connect to the camera. Some have suggested that this would be a problem because wifi is not available anywhere. This is not so because just about any device that has wifi can itself act as a wifi hotspot, even the cheapest android phones can nowadays.

The other major issue I have with it is that when in landscape mode it seems not possible to zoom in to the live view image. Maybe I just don;t know how or haven;t understood the manual but the only way I found to zoom in the landscape mode is to switch to portrait, zoom and then back to landscape which is unnecessarily cumbersome. I find it necessary to use landscape mode to have a large enough image to be useful for focusing so I have to keep switching between portrait to access the controls and landscape to be able to see the image in sufficient detail. Same applies for all the other controls by the way. I had in mind to make a mount to use the smartphone as a tiltable display but the lack of controls in landscape mode makes this impractical as I have to keep rotating the phone to switch between landcape and portrait.
Forum: Pentax K-30 & K-50 05-06-2014, 01:43 PM  
K-30 got wet, display flicker, autofocus issues
Posted By lister6520
Replies: 25
Views: 2,799
Rice is widely said to be a good drying agent but it is not reliable and not the most effective either. For starters rices is not always dry, especially if it is packaged in a porous cardboard box as it often is. It will have already been absorbing moisture for days or even weeks so will not be very effective.

The best drying agent I know of is calcium chloride. It is widely available at supermarkets as a 'refill' for small dehumidifiers that don't use electricity. The 'dehumidifier' being just a plastic container with holes or slots and you pour the 'refill' into it.

Just buy a bag of the stuff, empty it into a bowl, not filling more than half and place the bowl together with the camera into an airtight plastic box, the sort of which is used to preserve food. Alternatively just poor the stuf into the botom of the box and then place the camera on something to keep it out of contact with it. That way you have a larger surface area of the drying agent, making it more effective.

Placing the box in a warm, or even mildly hot location will speed up the drying process.

Also, remove the lens and open all ports/doors on the camera to ensure the vapour has an easy way out.
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