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Forum: Pentax News and Rumors 09-22-2019, 08:06 AM  
New K-series DSLR under development to be exhibited
Posted By dConvert
Replies: 3,487
Views: 270,534
On mine we're still on page 9.
I prefer to just scroll down rather than continuously switch to a new page, so opted for the longest possible pages :-)
Forum: Pentax Camera and Field Accessories 12-08-2018, 03:12 PM  
Tripod head for astro/DSO photography?
Posted By dConvert
Replies: 16
Views: 1,419
With a suitable wedge any tripod head suitable for the weight of lens & having a rotational ability should be workable.
The wedge basically mounts between the tripod & head & holds the head at the right angle for your lattitude. They are often homemade. :)
Forum: Pentax SLR Lens Discussion 08-01-2018, 09:08 AM  
How many lenses do you have?
Posted By dConvert
Replies: 1,792
Views: 152,627
She certainly knows I have LOTS OF CAMERA STUFF.
I doubt she knows just how many lenses I have around (or even how many bodies). Generally she just considers it permission to go & get something flash for herself. She also knows how cheap I am so probably assumes any lens I have will have cost under £20 - which might well be true for about 3/4 of my lenses.

I have been banned from bringing home any more photography books - so now have a filing cabinet draw full of them at work as well. After my Holidays I've decided to pass a few of my swaps on to friends at our camera workshop - that should give me back some space round my desk :o
Forum: Non-Pentax Cameras: Canon, Nikon, etc. 02-16-2018, 05:09 AM  
DSLR versus Mirrorless
Posted By dConvert
Replies: 47
Views: 3,026
Funny I've been shooting older mirrorless cameras for years & I've never found EVF DR to be a problem at all.
For action shots a DSLR works better than my mirrorless cameras, but they doesn't win in any other categories IMO.
For flexibility the mirrorless cameras are streets ahead.
Forum: Photographic Technique 02-09-2018, 09:29 AM  
Macro Extension with 1:2 macro lenses
Posted By dConvert
Replies: 20
Views: 2,868
Vivitar weren't the only ones to make macro focusing teleconverters my clubman ones must be more than just a rebadge of these as they are based around a 3x TC.


I prefer the results of the 2x set I have (which may be a rebadge of the ones you linked)
Forum: Photographic Technique 02-05-2018, 06:59 AM  
Macro Extension with 1:2 macro lenses
Posted By dConvert
Replies: 20
Views: 2,868
All these configurations will work & all will give different results.
TC+ET+Lens will give the highest magnification (assuming all extension tubes are the same length)
Extension tubes have more effect for shorter focal lengths so switching TC & ET will reduce the magnification but increase working distance.


I personally find stacking lenses to be an easier approach to ultra macro, with the wider lens reversed front to front with the longer one & the longer one mounted normally on the camera. Magnification is the ratio of focal lengths with both lenses focused to infinity, focusing the non-reversed lens closer will marginally increase magnification. (50mm reversed on 200mm gives 4x ) I always leave the reversed lens wide open & focused at infinity, anything else increases the chances of vignetting - which can be pretty bad with some lens combinations.

Have a look at Coupling lenses for extreme macro for a better written explaination, along with details on most of the other options...
Forum: Pentax SLR Lens Discussion 01-26-2018, 06:43 AM  
How many lenses do you have?
Posted By dConvert
Replies: 1,792
Views: 152,627
Well Monday was very much an exception. Previously I think 3 in a day is my maximum (a camera bag with 1 body & 3 Carl Zeiss lenses for £10).
I don't think I've ever made more than 2 separate lens purchases (i.e. lenses being sold separately) in on day.
Over the course of the last year It' only just averaged over 2 lenses a month, I was definitely buying more than that at one point!


None of my 21 look as nice as your examples. Most will fall into the forgettable category
Having a total of over 100 manual focus lenses does suggest it's time I started selling some on, especially as I don't have adapters for several of them, even for my mirrorless system.


I have to admit it's frustrating how often I've ended up second highest bidder - usually sniped in the last few seconds. With this job lot I increased my max bid (drastically) in the last 30s and would have lost out if I hadn't.

:mad: I wish e-bay would automatically extend auctions if there's a bid in the last seconds.
Forum: Pentax SLR Lens Discussion 01-24-2018, 12:33 PM  
How many lenses do you have?
Posted By dConvert
Replies: 1,792
Views: 152,627
That's exactly how many I added to my collection yesterday!
Admittedly there was only one (Tamron adaptal2 300mm macro - model 54B) of the job lot that I knew I wanted when I bid for them, but I subsequently found another that should prove pretty useful (a sigma 180mm macro). Most of the others are of very little worth, but as the set averaged to about £3.50 a lens I can have a go at servicing them & I won't have feel I've lost anything if I can't put them back together.

You don't have to be mad to have as many lenses as me, but if your significant other finds out it becomes a plausible excuse!
Forum: Pentax SLR Lens Discussion 12-07-2017, 06:00 AM  
Don“t know what to buy, need a zoom and a prime. Afraid because some lenses are old
Posted By dConvert
Replies: 23
Views: 1,496
I don't see any need to worry about lenses being old. If they've been reasonably well looked after old lenses work fine!
I'm also quite sure none of the lenses you're referring to would be classed as old in my collection.
Old suggests at least manual focus & probably manual aperture too - such as M & K series lenses & the earlier M42 mount ones - all work with the K1.
I've jury rigged a 1930's lens to use with my cameras (a Kodak 12cm Astigmat mounted via bellows). Apart from the lack of coatings in reality it's much the same as newer lenses...
Forum: General Photography 12-05-2017, 04:01 AM  
Is it just me, or do others find this equally offputting?
Posted By dConvert
Replies: 15
Views: 1,710
Having a choice of shutter speeds & apertures at 1 stop increments is a modern luxury. IIRC my box brownies have a single speed & just 2 apertures to pick from. OLD cameras often don't have any shutter speeds, relying on the photographer to uncover/cover the lens at appropriate timing.

:p
Forum: Pentax SLR Lens Discussion 12-01-2017, 06:04 AM  
throium glass lenses
Posted By dConvert
Replies: 60
Views: 5,410
Well the notes from my radiological protection supervisor training state that Semiconductor/Scintillation Detector should be used for solid samples while the GM tube is for gas. this could be because the scintillation detectors are considerably more sensitive.



Not a chance! You may have 50 radioactive lenses, but unless they've been contaminated or neutron bombarded you won't have even one that's highly radioactive.
I don't think any lenses have been produced that would be classes as moderately radioactive in the view of legislation. If it were it could not be legally sold to the general population.
It's almost certain that they would only be classified as low level.


FWIW in the UK the transport index for radioactively contaminated materials is 0 for anything up to 5µSv/hr, (~44mSv/Yr) this gives it the lowest category. It's possible that lenses fall below this being classed as exempt but this determination is based on the activivity in Bq/g & I don't have that data for doped lenses.
Forum: Pentax Camera and Field Accessories 11-29-2017, 09:34 AM  
Focal Reducer Availability
Posted By dConvert
Replies: 17
Views: 1,555
A focal reducer to take K mount lenses onto a k mount body isn't possible, but one to take medium format lenses would be. As is K mount lenses to MFT (I use one going via a EF mount) or K mount to Q-mount...


To work a focal reducer must mount the lens closer than it was initially designed to go so it's always impossible to have the same mount on both sides.
Forum: General Photography 11-29-2017, 07:38 AM  
How would you define the end of the film era?
Posted By dConvert
Replies: 63
Views: 3,373
Not for me! My first digital (1997?) was somewhat unimpressive, I continued to use my SLRs for any real photography for years afterwards.


I would consider the film era to be up to the point when digital photographs were more common than film ones. Not too far from 1900-2000, as before 1887 photography didn't use film (using bitumen, paper, glass or metal plates...) and it was only with the box brownie that film really took over.
Forum: General Photography 11-29-2017, 07:02 AM  
How would you define the end of the film era?
Posted By dConvert
Replies: 63
Views: 3,373
There have been scanning backs available for LF cameras for quite a few years. With the right subjects the results can be very impressive (or very quirky!). They are outside my budget but so is a new DSLR.
Forum: Pentax SLR Lens Discussion 10-16-2017, 08:10 AM  
throium glass lenses
Posted By dConvert
Replies: 60
Views: 5,410
Surely the no barrier readings include the beta & gamma sources which on the numbers you give (ignoring the +) constitute half the counts. Likewise the readings with the cap would include gamma. Giving:
100 mR/hr Gamma
150 mR/Hr Beta
250+ mR/Hr Alpha


Using the whole body weighting factor that converts to (moving to SI units)
1mSv Gamma
1.5 mSv Beta
2.5+ mSv Alpha


Even totaled that's well below the 0.1Sv threshold for detectable chromosome change. Unless you like licking your lenses the Alpha can be ignored - the bodies outer layer of dead skin stops most of this.
Forum: General Talk 10-16-2017, 07:18 AM  
What is the best drill bit? (Sarcasm )
Posted By dConvert
Replies: 279
Views: 14,225
Now that's what I call a proper drill bit!
The workshop here has a large format drill with something like a 1" or even 2" chuck, but AFAIK we haven't had anything like that in the company since we were sold off by Repsol in the nineties.


The LF drill needs serious support not a chance of handholding that baby at any speed!
Forum: Pentax SLR Lens Discussion 09-15-2017, 03:18 AM  
How many lenses do you have?
Posted By dConvert
Replies: 1,792
Views: 152,627
Of those that mount on my Pentax cameras currently 52 in some form of K mount, plus another 18 in M42 & 6 adaptall lenses.
Then there are enlarger lenses & the like that can be adapted...
There are a few K mount swaps I can safely get rid off but deciding which is the copy to keep has taken a long time :)
Numbers for my other camera systems (a Werra rangefinder, Micro 4/3s kit & 5x4 monorail) are less extensive
Forum: Non-Pentax Cameras: Canon, Nikon, etc. 08-30-2017, 08:52 AM  
Zenit Back With a Mirrorless body?
Posted By dConvert
Replies: 23
Views: 1,989
'An unnamed leading photographic equipment company will produce some of the components' this could just mean it has a Sony sensor (like Nikon/Pentax...)


I doubt it will beat the K1's performance but it might still be an interesting option...
Forum: Pentax K-30 & K-50 08-29-2017, 07:57 AM  
3rd party lenses
Posted By dConvert
Replies: 2
Views: 1,114
Nikon lenses have a slightly longer rear focal distance than PK mount. I've heard it is possible to get them to (miss)mount on a PK mount by turning them part way round. With the registration being slightly shorter than they are designed for the lens will then focus beyond infinity, loosing some of the close focus capability of the lens... Of course AF & electronic aperture will not be available with this.
I've not tried, but if miss mounting works the Nikon lenses could be used with a Pentax 1.7x AF teleconverter to give limited AF :D


There are two types of Adaptall2 K mounts, the PK version & the PKA version. Both work but the PKA is better giving camera control of aperture.
M42, T2, C/Y & medium format lenses can also be adapted readily to Pentax bodies in fully manual mode.
It is possible to jury rig adapters for many other lenses if infinity focus & auto features are not required.
Forum: Pentax DSLR Discussion 08-29-2017, 07:41 AM  
Question for those who wear glasses.
Posted By dConvert
Replies: 25
Views: 3,414
That's exactly what you should expect. With your glasses on they are providing the diopter adjustment. So having the viewfinder set for normal vision is right. Without your glasses the diopter setting allows the viewfinder to mimic the correction your glasses give.


If you have any other corrections in your glasses such as an astigmatism, it would be best to shoot with them.
Otherwise which ever is more comfortable.
Forum: Pentax SLR Lens Discussion 08-29-2017, 07:33 AM  
Third Party Lens Compatibility - M42 Mount
Posted By dConvert
Replies: 14
Views: 1,924
Ah, yes. I don't think any of mine fit that class.

:o
Forum: Pentax SLR Lens Discussion 08-29-2017, 07:27 AM  
Third Party Lens Compatibility - M42 Mount
Posted By dConvert
Replies: 14
Views: 1,924
I thought auto M42 lenses all used a simple pin on the back. when the pin is pressed in (or the lens is switched to M) the lens goes to the preset aperture. The rest of the time the lens remains wide open.


Some auto M42 lenses don't have the A/M switch, so need the pin pressed in to get to the set aperture (Some adapters have a ring to keep the pin pressed in)
Other M42 lenses don't have the auto facility at all - some of these have a double aperture ring. One of these rings setting the desired aperture, and the other actually moving the aperture blades from wide open to the position preset on the first ring.


AFAIK the stop down pin on all auto M42 lenses are compatible.
Forum: General Photography 08-29-2017, 05:54 AM  
Flickr Followers - as much a curse as a blessing?
Posted By dConvert
Replies: 61
Views: 5,027
Some of the people I follow are from knowing them in forums or in person. Others are because they often have images I want to look at...
When someone I don't know follows me, I take it as a minor complement, and will usually have a quick glance at their photostream/profile very rarely I see something making me follow them in return. If the person is following many thousands of photographers I generally don't bother even looking at their photostream, and would be most unlikely to follow them in return.


I think there have been a few who un-followed me after a few weeks when I didn't reciprocate. No loss in my book.
Forum: General Photography 08-29-2017, 05:46 AM  
Eclipse anomaly
Posted By dConvert
Replies: 15
Views: 1,448
The exposure is far too fast to get 2 distinct images from camera movement. There's no sign of blur on either of the images, so you can rule out camera shake.


I'm sure it's down to a reflection, if you only got it on some images I suspect the others were pointing more accurately at the sun so the reflection image is lined up with the other image.


The result is an impressive image.
:cool:
Forum: Pentax DSLR Discussion 08-23-2017, 01:52 PM  
The wrong focal length IBIS
Posted By dConvert
Replies: 11
Views: 985
The longer the focal length the more the sensor has to move to correct any movement. If the entered value is less than the actual focal length the movements will be in right direction but not big enough to cancel all shake. So a net improvement is seen.
If the focal length entered is slightly too high the sensor will move too much, but may still be an improvement on unstabilsed if the error is not too great.
I suspect if the focal length entered is more than twice the real focal length the corrective movement may become greater than the original shake making matters worse.

I believe the actual relationship will be down to FOV rather than focal length, but why complicate matters!
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