Forgot Password
Pentax Camera Forums Home
 

Showing results 1 to 25 of 127 Search:
Forum: Pentax SLR Lens Discussion 02-18-2013, 04:05 AM  
How to deactivate SDM and allow for screw drive autofocus with DA* 16-50mm f/2.8
Posted By sveinmb
Replies: 763
Views: 186,076
Just have to say a big thank you to the guys behind this fix!

I'm stunned that someone actually managed to reverse the firmware and made it possible to disable SDM. My DA* 16-50, known from the pictures in the previous (temporary) repair thread, is now a last permanently fixed from the dreaded SDM failure. :D
Forum: Pentax News and Rumors 02-08-2012, 02:32 PM  
K-mount lenses specifically designed for the K-01
Posted By sveinmb
Replies: 75
Views: 10,515
I guess it was just pretty damned irresponsible by Voigtl鋘der to create the 12mm f5.6 and the 15mm f4.5 for Nikon f-mount then. Not to mention Nikon with their own 6mm, 7.5mm, 8mm and 10mm fisheye lenses..
Forum: Pentax SLR Lens Discussion 02-13-2011, 10:03 AM  
Pentax DFA100WR vs new Sigma 150. Macro fight!
Posted By sveinmb
Replies: 23
Views: 5,474
As with all "what macro lens to buy"-discussions: the most important point to decide upon is what focal length you'll need/want. Compare the working distance at 1:1 macro both with and without the hood, and compare the DOF at that distance. I have both the Sigma 180mm and Tamron 90mm. Both give excellent results, but you're a lot closer to your subject with the 90mm and the 180mm will give a lot more washed out backgrounds at the same subject-to-background distance.

Check out this review of the Canon 100mm macro L IS and look at the examples of working distance and DOF vs the 180mm lens: Juza Nature Photography

In fact - all modern macro lenses from Pentax, Sigma and Tamron are great! There is almost no optical difference at all, perhaps with the exception of the Zeiss 100mm f2, said to have the highest resolution of any lens out there. If you really need WR you'll have to go with the Pentax. If you want to shoot subjects that might get scared, or want to isolate your subject as much as possible - get the one with the longest focal length.
Forum: Pentax SLR Lens Discussion 01-31-2011, 06:26 AM  
DIY SDM repair!
Posted By sveinmb
Replies: 200
Views: 82,649
I got a quote from Fovi at the time the lens first failed (2009). This was at the time when Pentax was restructuring its distributor and service network. I was told SDM lenses had to be to Germany for repair, and the cost was estimated to 2500-3000 NOK (about 400-500 usd).



I think moving the screw head/back part of the motor does something different. It's not about moving the rotor/shaft. I think you're actually moving other parts of the motor.

If this indeed is some sort of utrasonic motor it is based on principles of friction with a piezoelectric material, my best guess regarding the fault os : 1. Maybe something sticks inside and need a nudge to get free or 2. perhaps its the other way around, that it gets too loose and the ultrasonic vibrations can't move the rotor. I'll have to read up on these kind of motors to know more.

Someone also asked if it could be that the mechanical autofocus link to the camera body also rotates when the SDM motor runs, and that the SDM motor doesn't have enough grunt to pull all that. It's an interesting thought. Maybe someone could try to remove the screwdrive af shaft from the lens? If the theory is correct you might even get slightly faster focusing because of less restistance/friction?
Forum: Pentax SLR Lens Discussion 01-29-2011, 03:05 PM  
DIY SDM repair!
Posted By sveinmb
Replies: 200
Views: 82,649
"By popular demand" I've now made a guide with lots of pictures for those daring to try this themselves. Its found here
Forum: Pentax SLR Lens Discussion 01-29-2011, 03:04 PM  
DIY SDM repair!
Posted By sveinmb
Replies: 200
Views: 82,649
I can also confirm that twisting the focus screw does not help. I've used my lens on a K100D with its screwdrive af, and it was still dead using SDM on my K20D and K-7. Turning the SDM motor does something else obviously.
Forum: Pentax SLR Lens Discussion 01-24-2011, 03:54 AM  
DIY SDM repair!
Posted By sveinmb
Replies: 200
Views: 82,649
Sorry for not taking any pictures while I did this. I might consider dismantling it again tonight to create a full repair guide, but right now I'm just happy it's working :)

The photo at RH's blog show the SDM motor with its ribbon cable and the apparently glued screw head on top. (See the blue glue/epoxy/whatever around it) Notice that the gears both on top (in metal) and below (white plastic) did move just fine on my lens, but giving the motor itself some twisting through the back side screw head somehow made it work again.

The tap in the right circle on the picture is the af screw for cameras without SDM support, it's all connected through a series of metal and plastic gears.


Ayoh: just as I thought. That's why I didn't try any lubrication..

The next step will probably be to find a replacement oem motor that we can use in our lenses if a motor is beyond repair ? :) It wouldn't surprise me if it's actually a standard item that is not designed by Pentax from the ground up. For instance Shinsei Motor has some pretty similar designs in their lineup.
Forum: Pentax SLR Lens Discussion 01-23-2011, 03:46 PM  
DIY SDM repair!
Posted By sveinmb
Replies: 200
Views: 82,649
Good news everyone.. I just did a successfull repair on my defective SDM-focus DA* 16-50!

I recently got at tip about a blog post from [a certain banned user from this forum] that referred to another Chinese Pentax user on a forum thread who had successfully repaired his 16-50 with SDM failure. The repair is quite simple and consists of turning the back part of the SDM motor itself apparently to release it from a mechanical jam.

I admit, I din't have much belief in it, but decided to give it a go anyway. When the lens first failed (well over a year ago) I actually did dismantle it to check for errors myself, but I didn't dare to touch the small screw that seems to be glued on to the back part of the SDM motor. I assumed it was supposed to be a stationary item, and I didn't want to wreck it completely before sending it in for (the rather expensive) repair. OK, I didn't want to make a complete fool of myself to be honest. I did get a quote for repair abroad, and decided to put it on hold.

However, this Chinese guys success led me into giving the DIY attempt another go. The mechanics and plastic gears in the focusing part moved just fine with no apparent problems, just as it did the first time I opened the lens. I put a scredriver into the small screw head at the back of the motor and gave it a twist - and it moved slightly. The screw and the whole back part of the motor moves. It was really tight and not easy to turn, but I gave it a bit of massage back an forth before putting the lens together again. And, believe it or not - the lens focused again on my K-7! After well over a year just collecting dust and reminding me of really bad second hand deal, I now have a fully functioning DA* 16-50 again!!

Focusing now make a little bit of a squeeking noise, but the speed seems to be just as it was before it failed. I'm wondering if a bit of carefully added lubrication could make it even better and perhaps avoid it getting jammed again in the future. However I'm not sure exactly how the SDM motor is designed and I don't want to put lubrication onto parts that should not be exposed of it.

All in all I'm quite happy right now :) Having saved about 400 usd in repair costs, at least for now, and not having the dead DA* sitting on the shelf reminding me of a bad deal.. I wish I had dared fondling with the motor the first time I dismantled the lens though.


The original Chinese article can be found here (and google translate gives a nice chinglish mess of it): 在Wayli的启发下,我修理好了DA*16-50镜头SDM故障 - 无忌论坛

UPDATE: I've made a guide for this DIY repair online.
Forum: Flashes, Lighting, and Studio 10-09-2010, 11:29 AM  
P-TTL overexposure, no more negative flash compensation
Posted By sveinmb
Replies: 11
Views: 4,062
I've never noticed any major metering problems with A-series lens and the 540fgz. I have however noticed that it can, in certain situations, be difficult to get correct exposure with P-TTL flashgun at macro distances. In fact I've had better luck with TTL on my DS for macro.

The exposure has never been anywhere near 5 ev off though. Maybe 1 to 1.5 ev off, but not more than that.

Do you have any examples of subjects that get that amount of overexposure? A small white dot against a large black background? :)
Forum: Flashes, Lighting, and Studio 10-09-2010, 04:22 AM  
P-TTL overexposure, no more negative flash compensation
Posted By sveinmb
Replies: 11
Views: 4,062
There you have it then! You will not get P-TTL with a K, M or screwmount series lens. You need one from the A-series or newer.

It does not help to fool the camera to say that it is an A-lens when it isn't. The camera will not be able to meter and stop down to the correct aperture. A K/M-series lens is wide open until the camera pulls the aperture lever all the way down (green button/shutter). If you tell your camera it's an A-lens it will just pull the aperture lever down a slight amount to where the corresponding linear position of the right F-stop is.

The only way to get automatic flash with a K/M/Screwmount lens on Pentax is to either have a flash with built in auto sensor and use the correct manual settings according to it's table or use an ist D, DS or DS2 body with a TTL flash.

It *might* be possible to use a stopped down screwmount lens and let the camera meter it stopped down tricked to think it's an A-lens used wide open, but it will probably not be consistent and is not supported according to the manual.
Forum: Flashes, Lighting, and Studio 10-09-2010, 02:23 AM  
P-TTL overexposure, no more negative flash compensation
Posted By sveinmb
Replies: 11
Views: 4,062
Seriously, if you have to use -5 ev there is something wrong either with your camera, your flash or your settings. Are you sure it is even using P-TTL and not just full power?
Forum: Pentax DSLR Discussion 09-25-2010, 10:03 AM  
Pentax TTL bodies and Nikon flashes...
Posted By sveinmb
Replies: 12
Views: 4,162
That's a cool feature. I wasn't aware that it was able to light for just as long as the master flash. I thought it would just trigger and last for as long as you has set it to do manually. This is SU-4 automatic mode then?

Btw I think even the more expensive SB-800 is backwards compatible with an SU-4 mode.
Forum: Pentax DSLR Discussion 09-22-2010, 03:38 PM  
Creating a Photobooth with Pentax K-x
Posted By sveinmb
Replies: 5
Views: 12,060
For the K10D you might be able to use the source code for pkremote for full control. Pkremote is an open source utility for remote shooting with pentax (on linux). Of course you might be able to use Pentax remote assistant, if you can find a smart way to trigger your camera (without clicking at a certain spot on the screen) and then pick up every new image written to a folder on your harddrive.

Now if only Pentax would even bother to add tethering in their latest models.. :( not to mention trying to do it as good as Canon manages those tasks. Transmit raw in less than 3 seconds, full live view and manual focusing via usb is way cool. :D
Forum: Pentax DSLR Discussion 09-20-2010, 02:33 PM  
Creating a Photobooth with Pentax K-x
Posted By sveinmb
Replies: 5
Views: 12,060
I guess anything is possible, but the K-x will not be the simplest way to achieve just that. For instance no current Pentax DSLR have tethering capabilities to connect it to the computer while shooting. If you really want to, you could hack together a solution with a eye-fi wifi capable sd card and trigger the camera via cable remote and have some custom made software do the rest.

For this particular task though I think you'll probably be better off with a compatible camera from Canon or Nikon and some ready made photo booth software like PSRemote, NKRemote or DSLR Remote Pro from Breeze systems. I own a copy of DSLR Remote Pro myself. I've never used the photo booth feature though. Check out their website at Breeze Systems - Digital Camera Workflow Software: Browser, Downloader, Canon Remote Capture for more info. For all I know there may be other similar software out there as well.

Pentax have some great cameras in their lineup, but it's all a matter of finding the right tool for the right job I guess? ;)
Forum: Pentax News and Rumors 09-19-2010, 09:02 AM  
Official Pentax K-5 Specs !
Posted By sveinmb
Replies: 365
Views: 98,455
But that would just be two axis aka 2D. The K-5 must also show at what height you are at then ? :)
Forum: Pentax News and Rumors 09-19-2010, 05:32 AM  
P-ttl-2.0
Posted By sveinmb
Replies: 25
Views: 5,077
Let's say you want to underexpose the background a bit, have a main flash at full power at your subject and then a fill flash from the side to reduce hard shadows - you really want to control this manually! You would really want to have as fast shutter speed as possible to reduce ambient. If you go for the HS solution you're basicly telling the camera to please do something you would want it to do and then hope and pray that a quite unsophisticated metering system will do it right. Put on a snoot or grid etc and you'll really have to fight the controls to get whatever you're after.

HS flash is great if you're a point and shoot guy that just want to fill some face with a bright background. However it sux when you want to do any advanced lighting because you have no _real control_ over the exposure. The camera does all the calculations for you.

And of course, if you really need a lot of light, a hotshoe flash running at (very) reduced power through HS is not sufficient in the first place.

I do realize that the majority of users will never see this as a problem. The majority of users "never" use flash, they never use more than one flash, they never use the flash in manual mode and never use high power studio strobes either. But for a small segment of portrait/product/commercial photographers the manual flash sync speed is important. There might not be a big difference in 1/180 vs 1/250 but at least 1/250 would put Pentax up among it's competition where they have been for years.
Forum: Pentax News and Rumors 09-19-2010, 02:38 AM  
P-ttl-2.0
Posted By sveinmb
Replies: 25
Views: 5,077
Seriously, sync speed has nothing to do with *TTL. All communication between flashes are done before the camera opens its shutter. If it would send data flashes during the exposure you would have (slight) inaccuracy in the exposure itself. I can't believe Pentax would have made such a weird design in the first place.

And my usual rant: Those who need higher sync speeds use their flashes in manual mode, either hotshoe flashguns or studio strobes. If Pentax would present 1/250 sync as P-TTL only they have effectively killed all potential studio/portrait/strobist buyers.
Forum: Pentax News and Rumors 09-10-2010, 03:10 PM  
Possible Complete K-5 Specs (Still rumour until the 22nd!)
Posted By sveinmb
Replies: 465
Views: 100,612
Your theory is somewhat correct, but no flash in the world is anywhere near as slow as that. A flashgun (or studio flash) will empty its full charge in less than a millisecond.



You're right. The entire sensor have to be visible while the flash emits light. That's what makes it so damn difficult to create a camera with a high sync speed. The shutter curtain would have to travel extremely fast. In fact some older DSLRs (Nikon D70, D40? and one of the early Canons) actually had an electronic shutter that allowed for a lot higher sync speeds of 1/500s+
Forum: Pentax News and Rumors 09-10-2010, 11:48 AM  
Possible Complete K-5 Specs (Still rumour until the 22nd!)
Posted By sveinmb
Replies: 465
Views: 100,612
Sorry, I just don't buy the rumor with flash sync > 1/180s for newer flash units only. It makes absolutely no sense as it would be useless for any semipro or pro photographers using pocketwizards or studio lighting with pc sync cords.

Either the camera allows for flash trigging over 1/180s or it don't. It's just a matter of shutter timings. To make > 1/180s only available in a P-TTL secret/proprietary mode would be a sure way to tell all customers in this segment to stay away from Pentax in all foreseeable future.
Forum: Pentax DSLR Discussion 08-28-2010, 02:53 PM  
How Will A K-7 or K-X Make These Pictures Look Better?
Posted By sveinmb
Replies: 26
Views: 4,868
No. :)

On the web or prints no larger than A4 you'll have no benefits with higher resolution sensor. However if you crop your images, there is a big difference in having a 2 megapixel or a 6 megapixel cropped result regarding how much detail is left in the image.

I don't think you should consider an upgrade for the megapixels alone. The K-7 is for instance a much more solid body, a lot faster autofocusing, better auto white balance, a lot better lcd screen, two control wheels (more direct control without looking for buttons), faster and more responsive menus, live view, much larger buffer (don't have to wait that much), weather sealing etc.

I've barey used the K-x and to me it didn't feel all that different from my K100, but it surely captures more details if you zoom in to 1:1.

The K100D is a very nice little camera capable of excellent image quality. Some still praise it for its vivid colors and noise free images even at largish iso values. I warn you however - if you buy a K-7 you'll never look back regarding how it handles and feels in your hand each time you're out shooting.. (but you might remember how much fun it was back when 6 megapixel images were completely noise free at 1:1 zoom level)
Forum: Pentax News and Rumors 08-26-2010, 08:55 AM  
Articulating LCD ?
Posted By sveinmb
Replies: 89
Views: 16,254
I would love an articulating screen. It makes macro shooting a lot less painful. Liveview is perfect for macro, and having a tiltable/movable screen would make it even better. I for one would prefer if it came in a semi pro body.

I'm not sure everyone has thought about it, but for now there is a workaround for doing those difficult angles with lv: a portable dvd player with a video input! It has a lot less resolution and it's an extra item to carry with you, but I guess it's cheaper than buying a canon, nikon, sony or olympus with corresponding lens..

Everyone else has it - why shouldn't Pentax offer it as well?
Forum: Non-Pentax Cameras: Canon, Nikon, etc. 08-26-2010, 08:35 AM  
Rearranging my kit(s)
Posted By sveinmb
Replies: 34
Views: 7,357
As one who own way too much lenses myself, I'll give give a bit of tough love regarding your lineup :lol:

Why keep the Helios 44K? It's not really fast, it's not very practical (green button only), and it's not that much longer than the 50mm ? The 50 1.2 and the 77 1.8 would probably be the lenses you'll grab anyway?

There is also the question of the 35 macro. If you use it for macro, fine, otherwise I would guess the 31ltd would do the job perfectly.

I wouldn't bother with the DA40 if I already had (and liked) the FA43. I went for the DA40 myself as I didn't feel too comfortable with the oof rendering of the 43 wide open, but can't see the point in having both. One of them is bound to become a dust collecting item.

The 21 is a nice thing to have though. Great for general shots without screaming "wideangle" to the viewer.
Forum: Pentax News and Rumors 08-24-2010, 03:08 AM  
Brief info about K-5 and KR
Posted By sveinmb
Replies: 569
Views: 119,119
I never knew my K-7 was that bad :(
Forum: Pentax News and Rumors 08-23-2010, 05:25 AM  
Any chance of Limited lenses with SDM?
Posted By sveinmb
Replies: 60
Views: 10,249
I've disassembled a 16-50mm with defective SDM, and to me the mechanical parts did not seem inferior to other contemporary lenses. I came to the conclusion that either the motor itself had died or the electronic components controlling it.

Based on the fact that the focusing got gradually worse before complete failure, instead of just dying instantly, I would suspect it was the motor itself that was the problem.
Forum: Pentax DSLR Discussion 08-17-2010, 10:37 AM  
K-x, Smc-m, and built-in flash
Posted By sveinmb
Replies: 6
Views: 1,689
Like egordon99 said, you'll need a TTL-compatible external flash. The older TTL (not P-TTL) models goes for very reasonable prices, I've bought several 500ftz flashes myself. I also have the 080c macro ring flash and it performs great with the DS.

I think it's a shame Pentax dropped the TTL-sensor in their higher end models, it can't add much to the cost of the body. Although the P-TTL system is a lot more advanced on paper at least, there are certainly benefits with the older TTL-system as well. It's a typical move done by all camera makers to force customers to buy new accessories.
Search took 0.01 seconds | Showing results 1 to 25 of 127

 
Forum Jump


All times are GMT -7. The time now is 04:16 PM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top