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05-08-2008, 07:02 PM   #46
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QuoteOriginally posted by Wheatfield Quote
snip....
My understanding from talking to people close to Pentax is that the green button thing is the best we can hope for, the aperture simulator is gone for good.
it's not an issue of the apature simulator or green button. The green button works perfectly on the *istD, and the activated metering and DOF preview on all pentax DSLR's lets metering work in good fashion, except on the K10D and K20D, where the reflection off the viewfinder screen to the metering sensor, behaves differently from other cameras (or more specifically viewing screens) the solution, and there are a few are as follows:

- offer a retrofit, to an older viewing screen that works, plus sopftware upgrade so your AE lenses, which have a built in fudge factor will work properly with the corrected viewing screen, or
- enter min and max apature and let the camera control the apature, in AE mode. This would require changing, with non AE lenses the movement as Manual lenses have apature change diameter as a function of motion, not area as KA mounts and later do.
QuoteQuote:
For myself, I would love to see a Pentax DSLR that solves all the problems, but I am pretty sure that it would probably be double the street price of a K20, which would certainly limit sales.
this is BS. it is software we are talking about here, not unit material costs, and I am takling about defficiencies in the K10 and K20 we are already paying the price so why can't we have the performance
QuoteQuote:
The K10/K20 aren't perfect to be sure, but for the price being asked, they are remarkably capable instruments.
I don't disagree, but regardless of how capable they are, a camera that is marketed as being able to use one of the 23million lenses they ever made, but which can't meter as well as the first DSLR they made using those very same lenses is not acceptable.

05-08-2008, 07:33 PM   #47
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QuoteOriginally posted by Lowell Goudge Quote
this is BS. it is software we are talking about here, not unit material costs, and I am takling about defficiencies in the K10 and K20 we are already paying the price so why can't we have the performance ....
Perhaps my standards of what a camera should be just eclipse yours. I am talking material costs as well as software cots, since much of the camera's performance limitations (in my view) would be solved with higher specified components.

You may see some of your firmware wishes if Pentax decides that it is economically viable. I expect you can forget about them supporting third party teleconverters though, they have no control over what SIGnificant MAlfunction and others put on the market, and probably see no advantage to support companies that do little other than reverse engineer other peoples work for profit.
Apparently there is a teleconverter in the lens roadmap, so don't give up hope for teleconverter support yet, though you may not like the price of admission (buying real Pentax rather than third party junk).

I'll test the exposure accuracy of my K20 with some K and M series lenses and post my results in a few days.
05-09-2008, 06:37 AM   #48
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QuoteOriginally posted by Wheatfield Quote
You may see some of your firmware wishes if Pentax decides that it is economically viable. I expect you can forget about them supporting third party teleconverters though, they have no control over what SIGnificant MAlfunction and others put on the market, and probably see no advantage to support companies that do little other than reverse engineer other peoples work for profit.
Yeah, except that the same thing needed to support their OWN TCs is needed to support third-party TCs. I admit I have a Tamron TC, but how many of the people asking here own Pentax TCs? Probably quite a high percentage.

As to SIGnificant MAlfunction - It seems like lately it's Pentax glass that has the problems. (See all the reports of QC problems with the DA* 16-50.)
05-09-2008, 06:59 AM   #49
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QuoteOriginally posted by Wheatfield Quote
Perhaps my standards of what a camera should be just eclipse yours. I am talking material costs as well as software cots, since much of the camera's performance limitations (in my view) would be solved with higher specified components.

You may see some of your firmware wishes if Pentax decides that it is economically viable. I expect you can forget about them supporting third party teleconverters though, they have no control over what SIGnificant MAlfunction and others put on the market, and probably see no advantage to support companies that do little other than reverse engineer other peoples work for profit.
Apparently there is a teleconverter in the lens roadmap, so don't give up hope for teleconverter support yet, though you may not like the price of admission (buying real Pentax rather than third party junk).

I'll test the exposure accuracy of my K20 with some K and M series lenses and post my results in a few days.
I don't think there is an issue with "higher specification materials" the issue here (teleconverters) is not related to that, simply related to providing a menu to add a TC factor, or pick from the list) similar to the selection of focal lenghts presently.


For K mount lens metering, the issue is really caused by the super bright viewing screen introduced in the K10D and K20D. and while this hardware part introduces errors, they can be fixed in software. Note that if you take an A series or later lens, and put it in manual it meters poorly, but in Automatic mode it meters correctly. The difference is only that in AUTO mode the camera knows the wide open apature, and apature range, and can adjust for the error introduced from the viewing screen.


As for third party junk, I will admit that I have lots of it, Sigma 2 lenses and 2 TCs, Tamron 2 lenses. Vivitar 2 lenses, 2 TCs, 3 extension tubes. All of it, while not carrying the pentax name, performs very well, and many of the items perform exceptionally for the price paid.

Whether I will purchase any new pentax lenses remains to be seen, I own 8 pentax lenses presently, plus 2 flashes, two TCs, and 4 bodies. Again I am satisfied with all of them.

The reason I have so much third party "junk " as you put it, is because much of this junk was purchased to fill voids that exist NOW, and have existed in their product line up for some time. I would quite probably own more pentax and less third party if the products were competitive and available, BUT as a "non conformist" i.e. not a canikon owner, I selected pentax because they were the best value in the price performance curve for me, and always have been. I look at lenses the same way, and really have only purchased one lens in the past 4 years where I selected third party junk over pentax where the product actually existed in pentax, that was my taking of a sigma 10-20 over a pentax 12-24. None of my other lens purchases are products currently marketed by pentax.


Last edited by Lowell Goudge; 05-09-2008 at 07:09 AM.
05-09-2008, 01:26 PM   #50
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I have a SDM compatible tele converter
Well actually it is a power zoom compatible 1.7x Soligor but DA* 50-135 SDM focusing works like a charm. Too bad Pentax choose not to support tele converters
Bad Pentax.
05-09-2008, 01:32 PM   #51
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QuoteOriginally posted by Matjazz Quote
I have a SDM compatible tele converter
Well actually it is a power zoom compatible 1.7x Soligor but DA* 50-135 SDM focusing works like a charm. Too bad Pentax choose not to support tele converters
Bad Pentax.
The question is, how is th emetering?

Are you using this on the K10D or K20D? because the other issue with TC's, although we have not hit upon it yet, so I will introduce it now, is that with the K10, due to the inconsistency of exposure with manual lenses, and the correction factor thay put in software to correct based upon maximum lens apature, adding a TC will also impact exposure.

I tested my Sigma 70-200 F2.8 woith both 1.4x and 2x TCs, and the exposure went from perfect to +1 stop. Right where the lens alone metered in Manual Apature.

with a 1.7x you will have a bigger exposure error, again because the camera will think you have an F2.8 max apature as opposed to F4.5, (apature data passed streight through without modification)
05-09-2008, 06:42 PM   #52
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QuoteOriginally posted by Lowell Goudge Quote
it's not an issue of the apature simulator or green button. The green button works perfectly on the *istD, and the activated metering and DOF preview on all pentax DSLR's lets metering work in good fashion, except on the K10D and K20D, where the reflection off the viewfinder screen to the metering sensor, behaves differently from other cameras (or more specifically viewing screens) the solution, and there are a few are as follows:

- offer a retrofit, to an older viewing screen that works, plus sopftware upgrade so your AE lenses, which have a built in fudge factor will work properly with the corrected viewing screen, or
- enter min and max apature and let the camera control the apature, in AE mode. This would require changing, with non AE lenses the movement as Manual lenses have apature change diameter as a function of motion, not area as KA mounts and later do.
this is BS. it is software we are talking about here, not unit material costs, and I am takling about defficiencies in the K10 and K20 we are already paying the price so why can't we have the performance I don't disagree, but regardless of how capable they are, a camera that is marketed as being able to use one of the 23million lenses they ever made, but which can't meter as well as the first DSLR they made using those very same lenses is not acceptable.

Ok, I tested a few lenses. A K55/2, a K50/1.4, an M85/2, and an FA50/1.4 (using the aperture ring).
All displayed the following (good exposure wide open, over exposed (1-probably 2- stops, I didn't actually check histograms, just thumbnails in Bridge) through the range, and then at minimum aperture good exposure again.
For fun, I replaced the focusing screen with the original screen from my istD and retested the FA50/1.4, with identical results.
So, while it appears that there is a metering problem with the K20 and lenses using the aperture ring, it does not appear to be related to the focusing screen, nor does it seem to matter if it is a newer lens or an older one.

Last edited by Wheatfield; 05-09-2008 at 06:57 PM.
05-10-2008, 05:02 AM   #53
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QuoteOriginally posted by Wheatfield Quote
Ok, I tested a few lenses. A K55/2, a K50/1.4, an M85/2, and an FA50/1.4 (using the aperture ring).
All displayed the following (good exposure wide open, over exposed (1-probably 2- stops, I didn't actually check histograms, just thumbnails in Bridge) through the range, and then at minimum aperture good exposure again.
For fun, I replaced the focusing screen with the original screen from my istD and retested the FA50/1.4, with identical results.
So, while it appears that there is a metering problem with the K20 and lenses using the aperture ring, it does not appear to be related to the focusing screen, nor does it seem to matter if it is a newer lens or an older one.
you need to measure the grey scale against a uniform lit surface, otherwise you can be easily fooled by the results and histograms. Note a correct histogram is 110 greyscale for the metering on a uniform surface, and you should use spot metering for the tests.

Note many have reported that changing out focusing screens changes the metering on the K10D. so again checking greyscales is critical in this.

Also, I ran a test with some of my "junk" lenses and TC's. The K10 has an exposure error even in AE mode of between 1 and 1 1/2 stops with the 1.4 and 2x TCs installed. Oddly enough this is the same error that is present in metering when you stop down from F2.8 to F4 or F5.6 with the lens in manual mode. From this I can also conclude that the simple pass through of apature information from the lenses by the TC, without the camera knowing a TC is present, also introduces exposure errors. I will test today using my two pentax TC's, both 1 K mount 1 KAF mount to see if they do the same thing.

It still comes back to pentax MUST accomodate for teleconverters in the K10D and probably K20D. As well they MUST fix the exposure errors because they are fundamental defects with the cameras.

05-10-2008, 08:23 AM   #54
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Sorry Lowell, I'm a photographer, not a measurbator. I don't need to test beyond what makes a pleasing picture. Anything else is a waste of my efforts. I did, however, get curious this morning and check the EV range of what I did last night, and concluded that I had probably dropped outside the metering range of the camera during my test, so I repeated it this morning in full sun with a K50/1.4.
The EV range ran from aroung EV11 to EV4, which is all within the meter's range, and came up with some variance, but not enough to render the images unprintable, were I in the mood to print pictures of my sidewalk.

If you are running any sort of test of the stop down metering, make sure you aren't running the meter out of range. It is very easy to do.
I have shot some excellent pictures with my K lenses on the K10, so I'm not overly worried about their usability, and am very satisfied with the level of compatability that Pentax has maintained, especially when you compare it to the non existent compatability that Canon, Sony(Minolta) and Nikon has with their old lenses. We can still mount our lenses and use them, even with the inconvenience of less than accurate metering.
I'm not seeing how Pentax MUST fix anything, that is pure hubris on your part. If you don't like the equipment, change brands to something you like better.
I find that my A series teleconverters work just fine, BTW, although with a lens kit that goes from 10mm to 600mm, I rarely use the things.
05-10-2008, 09:09 AM   #55
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QuoteOriginally posted by Wheatfield Quote
Sorry Lowell, I'm a photographer, not a measurbator. I don't need to test beyond what makes a pleasing picture. Anything else is a waste of my efforts. I did, however, get curious this morning and check the EV range of what I did last night, and concluded that I had probably dropped outside the metering range of the camera during my test, so I repeated it this morning in full sun with a K50/1.4.
The EV range ran from aroung EV11 to EV4, which is all within the meter's range, and came up with some variance, but not enough to render the images unprintable, were I in the mood to print pictures of my sidewalk.
the point is not to "pring pictures of my sidewalk, or to be a measurebator, but to have accurate characterization of my equipment so that I get the photo's I want.
QuoteQuote:
If you are running any sort of test of the stop down metering, make sure you aren't running the meter out of range. It is very easy to do.
I have shot some excellent pictures with my K lenses on the K10, so I'm not overly worried about their usability, and am very satisfied with the level of compatability that Pentax has maintained, especially when you compare it to the non existent compatability that Canon, Sony(Minolta) and Nikon has with their old lenses. We can still mount our lenses and use them, even with the inconvenience of less than accurate metering.
I find the inconvenience as you put it unacceptable, not because it is there, but because my *istD meters properly. What I have difficulty accepting is not advancing technologies, but differing performance of one of the three fundamentally basic functions a camera/system should do. I rate these as follows:
1) have an accurate shutter across all speeds
2) control the apature of the lens across all apature settings
3) have accurate metering of the light with all lenses that are intended to work on the camera.

the error I am measuring cannot be from exceeding the metering range. From wide open on a 50mm F1.4 to F8 on a bright sunny day, is a range of only 5 F stops, yet there is a shift in exposure of 3 strops moving from under exposure to over exposure and it does not matter if this is a sunny dat or a darkly lit room, the camera always under exposes at f1.4 and over expopses at F8/
QuoteQuote:
I'm not seeing how Pentax MUST fix anything, that is pure hubris on your part. If you don't like the equipment, change brands to something you like better.
I find that my A series teleconverters work just fine, BTW, although with a lens kit that goes from 10mm to 600mm, I rarely use the things.
If you look at the three fundamentals, they are failing badly on # 3 where previous cameras work.

I do not consider a variation across the apature range of my 50mm F1.4 from -1.5 to +2 stops in metering an accurate light meter.

Can I print pictures yes, but when shooting in other than ideal flat light with limited contrast, the errors in metering become serious

Last edited by Lowell Goudge; 05-10-2008 at 09:35 AM.
05-10-2008, 01:46 PM   #56
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Your fundament #3 is pretty much a straw man.

I can't speak to the accuracy of the shutter timing of any camera.

Without an aperture cam follower, the camera has absolutely no way of controlling the lens aperture. This is something that did not migrate to the DSLR family, and you knew this when you bought in, or would have, had you taken the time to educate yourself.
Pentax put their cards face up on the table that old lens functionality was taking a back seat as long ago as 1997 when they introduced the first crippled mount MZ series film camera.

One of the other forums I read had a very succinct answer to this conundrum which is to set your shutter speed and f stop to where you think it should be, based on experience, take a test shot and then tweak things until you like it. If convenience is of the essence, you should be using at least an A lens, and preferably an AF lens.

Also, I just shot this series with an M200 f/4 on the K20D. The labels on the pictures are an accurate descriptive. This was done in manual mode/green button. other than my sensor being somewhat dirty, and shake reduction not being so good with a 400mm lens and a 1/10 second exposure, it looks pretty even to me, certainly within the expectations of any normal photographer.
I did not reset shake reduction when I put the teleconverter on. As far as the camera was concerned, it was still a 200mm lens.
I'm just not seeing any problems here.

Last edited by Wheatfield; 02-05-2011 at 08:45 PM.
05-10-2008, 02:35 PM   #57
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QuoteOriginally posted by Wheatfield Quote
Your fundament #3 is pretty much a straw man.

I can't speak to the accuracy of the shutter timing of any camera.
many photo magazines used to report on this, and typically the error was less than 1/3 stop, with the possible exception of above 1/4000.
QuoteQuote:
Without an aperture cam follower, the camera has absolutely no way of controlling the lens aperture. This is something that did not migrate to the DSLR family, and you knew this when you bought in, or would have, had you taken the tme to educate yourself.
I knew full well what the camera was supposed to do, as I already had an *istD. In fact, the camera does accurately control the apature correctly for new lenses, apature on all KA-J mount lenses is ONLY controlled by the body, and the apature activation arm, in fact, this began in the early 1980's with the A series lenses. It is not a question about this, or being educated. Additionally, with K mount lenses, the apature is set very accurately with the lens itself, therefore there is no issue other than metering which works perfectly on the *istD but DOES NOT on the K10D.
QuoteQuote:
Pentax put their cards face up on the table that old lens functionality was taking a back seat as long ago as 1997 when they introduced the first crippled mount MZ series film camera.
that is not at issue, as I said earlier, I can accept a certain amount of technical advancement, what I cannot accept is a product problem being written off as "advancement"
QuoteQuote:
One of the other forums I read had a very succinct answer to this conundrum which is to set your shutter speed and f stop to where you think it should be, based on experience, take a test shot and then tweak things until you like it. If convenience is of the essence, you should be using at least an A lens, and preferably an AF lens.
While I understand part of this, what I can't accept is that a function which is advertised, as compatible backwords, and which worked on the very first DSLR, no longer does with any measure of precision.

We are dealing with a fundamental defect in the metering, on a function that in the manual is claimed to work and on previous versions of their DSLRs did with remarkable accuracy. This is after all their flagship product, not the bottom end entry level camera.

Don't get me wrong about the camera. Aside from this issue, I enjoy using it, it is just frustrating that something which is so fundamentally simple to fix, one or two lines opf code in the software, is being ignored.

Pentax elected to make the camera compatibie. they did noit have to, that was a choice, they need to accept, however, having gone that route, some criticism for making a small error on the K10D,

The same is true of teleconverters, again 1-2 lines of code, no big deal and it would make their cameras even better.

I am not arguing here for faster autofocus , faster frame rates, rediculous ISO settings, and all the other things that are hardware dependant, just some modified software to resolve an issue pentax themselves introduced with the K10 on metering, and forgot about with respect to SR. It is not reinventing the wheel, it is just making their product better. SHouldn't they be striving for that.
05-10-2008, 03:18 PM   #58
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Apparently you missed the pictures.
The problem, while noted, is not 100% repeatable.
Judging from my results, the metering error is being induced by a loss of metering accuracy at lower light levels. This might explain why my pictures shot last evening and this morning in shade show the problem while the ones I just shot in full sunlight (several EV brigher conditions) do not.
This would also explain why I have not run into this before, as the rare times I have shot with a K lens on the K10, it has always been in bright light conditions.
The manual lists the lower range of the meter as EV-0, it would appear that accuracy may be compromised several steps above that, at least with non A lenses.

I keep hearing this 1-2 lines of code stuff. Sorry, I'm not buying into it. If it were that easy, then they would have done it to avoid the kind of whinging from customers that this thread seems to be about.
05-10-2008, 03:52 PM   #59
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QuoteOriginally posted by Wheatfield Quote
I did not reset shake reduction when I put the teleconverter on. As far as the camera was concerned, it was still a 200mm lens.
I'm just not seeing any problems here.
SR with a teleconverter reporting the wrong focal lens (our situation) is only gradually loosing its efficiency depending on the magnification factor.

SR with the correct focal length is said to give 3-4 stops, or a factor 8-16 in shutter speed. To simplify things here, let's say a factor 10. Or again put differently, it passes 10% of the shake uncorrected, so to speak.

Now, with a TC, the 90% will be undercorrected.

So, with a 1.4x TC, remaining shake will be 10% + (1-1/1.4)*90% = 36%.
Or a factor 2.8 which is 1.5 stops (0.9 stops for a 2x TC).


Summary:

A TC degrades SR efficiency from 3-4 stops down to about 1 stop.
05-10-2008, 04:06 PM   #60
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I see your math skills are quite good, but I'm not believing your summary. It just doesn't feel right to me.
Have you proven this on anything other than paper?
I'm thinking there is a more direct correlation, such as an unreported doubling of focal length might (or might not) represent a 50% reduction in SR efficiency.
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