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06-08-2012, 02:25 PM   #16
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I had considered the Sigma 17-70 but from the photozone.de reviews for both 17-70s, it seems the pentax is superior in every almost respect.

06-08-2012, 06:15 PM   #17
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QuoteOriginally posted by mikemike Quote
So I haven't seen anyone sing the praises of the DA 17-70 over the Tamron other than the superior metering functionality.
I believe you have been misinformed regarding the "superior metering functionality". I cannot believe that the Tamron 28-75/2.8 does not supports matrix metering. I have many third party lenses (Tamron, Sigma) and they all support matrix metering.

It would be good if a Tamron 28-75/2.8 owner would confirm that the lens supports matrix metering.
EDIT: Thanks, rawr, for confirming that your lenses support matrix metering (as expected).

I furthermore believe that third-party lenses will cooperate with Pentax flashes just like Pentax lenses.

The only limitation of third-party lenses I'm aware of is that Pentax cameras do not support in-camera lens corrections with them. That's no disadvantage to me as I'd never leave such things to be baked into a JPG in an automated manner. I'd always to that when doing a RAW conversion. This will work with any lens, third-party or not.

Last edited by Class A; 06-09-2012 at 08:45 PM.
06-08-2012, 08:51 PM   #18
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QuoteOriginally posted by Class A Quote
I cannot believe that the Tamron 28-75/2.8 does not supports matrix metering. I have many third party lenses (Tamron, Sigma) and they all support matrix metering.
They may appear to, the EXIF may even say so, but...

Name:  metering.gif
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(p-117 of the K-5 manual, similar in any other Pentax manual)
06-08-2012, 11:34 PM   #19
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QuoteOriginally posted by rawr Quote
(p-117 of the K-5 manual, similar in any other Pentax manual)
We had that discussion before in another thread.

Wheatfield said it best
Pentax can't, and won't take responsibility for how non Pentax equipment will operate, so they don't acknowledge the existence of no Pentax equipment in their literature.
The wording in the manual does not mean that third-party lenses do not support matrix metering.

Note that the manual does not say "non-Pentax" lenses. Also note that third-party lenses can functionally be "FA", "A", etc. lenses as well, even if their model label does not contain these letters. My Sigma 70/2.8 EX Macro, for instance is to all intents and purposes an "FA J" lens, and of course it supports matrix metering.

Sigma and Tamron implement Pentax's digital protocols in order to support conveying focal length, aperture ranges, HSM-based focusing, etc. Why would they not support matrix metering?

06-09-2012, 07:48 PM   #20
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QuoteOriginally posted by Class A Quote
Sigma and Tamron implement Pentax's digital protocols in order to support conveying focal length, aperture ranges, HSM-based focusing, etc. Why would they not support matrix metering?
It depends on their ability to clone or reverse-engineer Pentax's lens to body communications protocols, I guess. Tamron and Sigma do seem pretty good at it - maybe Pentax is more open to reverse engineering than other camera makers.

Other camera makers note that limitations exist on lens support for advanced AE metering schemas like matrix metering - for example from the D800 manual, it says that the body will default to centre-weighted if the lens isn't capable of giving the body certain information:

'With non-CPU lenses, camera uses color matrix metering if focal length and maximum aperture are specified using Non-CPU lens data option in setup menu (p 213); otherwise camera uses center-weighted metering.'

But in examining the EXIF data from the K-5 with it's 77 metering segments from Tamron or Sigma lenses alongside my Pentax lenses, when matrix metering is switched on when using either a Tamron, Sigma or Pentax brand lens, I do indeed see something like this, which highlights that no matter what brand lens is used, each of the 77 AE metering segments is indeed recording data:

QuoteQuote:
Camera Model Name : PENTAX K-5
Exposure Time : 1/200
F Number : 8.0
Focal Length : 70.0 mm
Metering Mode : Multi-segment
Lens Type : Sigma
SR Focal Length : 70 mm
Metering Mode 2 : Multi-segment
AE Exposure Time : 1/186
AE Aperture : 8.0
AE Metering Segments : 9.3 8.4 8.5 7.6 8.6 9.8 9.4 9.3 8.8 9.0 9.8 9.3 8.0 7.9 7.6 7.9 9.3 8.9 8.9 8.4 8.8 10.1 10.9 10.6 9.5 8.9 8.5 8.6 8.8 9.1 9.1 9.3 10.1 10.9 10.3 9.9 8.9 9.3 8.1 8.9 9.4 9.8 10.5 10.9 10.8 10.4 9.9 7.9 7.6 9.0 8.6 8.1 8.8 10.8 11.1 10.0 9.3 8.8 8.3 8.9 9.4 8.8 9.9 9.5 9.4 10.4 10.4 10.1 10.1 9.9 9.6 8.6 9.9 10.0 9.8 8.3 9.0
Flash Metering Segments : 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Slave Flash Metering Segments : 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

etc
But I do find that my cameras meter more accurately when using matrix mode with Pentax lenses attached than when using my Tamron or Sigma lenses - eg shooting my Tamron 17-50 vs my DAL 18-55 under similar light in similar scenes always produces significant under-exposure in the Tamron especially in challengingly lit scenes. If a Pentax lens is mounted, the way the camera processes the exposure data works as you would expect matrix metering should. That's why I sometimes leave the Tamron at home and use the Pentax kit lens, for example. Light and dark areas are better balanced in normal shooting, and especially flash.
06-09-2012, 08:41 PM   #21
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QuoteOriginally posted by rawr Quote
'With non-CPU lenses, camera uses color matrix metering if focal length and maximum aperture are specified using Non-CPU lens data option in setup menu (p 213); otherwise camera uses center-weighted metering.'
That's fine and is in accordance with what the Pentax manual says, but we are dealing with CPU equipped lenses, so the above quoted passage is not applicable.

QuoteOriginally posted by rawr Quote
But in examining the EXIF data from the K-5 with it's 77 metering segments from Tamron or Sigma lenses alongside my Pentax lenses, when matrix metering is switched on when using either a Tamron, Sigma or Pentax brand lens, I do indeed see something like this, which highlights that no matter what brand lens is used, each of the 77 AE metering segments is indeed recording data:
And that's what counts. Thanks for confirming this.

@mikemike
Did you see that? No reason to eschew third-party lenses because they are not metering as well as the Pentax ones.

QuoteOriginally posted by rawr Quote
But I do find that my cameras meter more accurately when using matrix mode with Pentax lenses attached than when using my Tamron or Sigma lenses - eg shooting my Tamron 17-50 vs my DAL 18-55 under similar light in similar scenes always produces significant under-exposure in the Tamron especially in challengingly lit scenes.
I wonder whether this observation would withstand systematic evaluation. There is no reason why metering should work better for one lens than another.

One could suspect Pentax sabotaging proper metering once a third-party lens is recognised but
  1. I do not believe Pentax would resort to such malicious tactics. With its comparatively spartan lens selection, Pentax needs third-party lens offerings to have a viable selection of lenses. It would be foolish of Pentax to cripple third-party lenses with sub-par metering. Not providing a goodie (in-body lens correction) is one thing; crippling metering would be another.
  2. Sometimes the camera may not even have a way of knowing whether the lens is third-party or not. Sometimes third-party manufacturers reuse Pentax lens IDs so the camera may be convinced that a Pentax lens is mounted. I'm not sure which firmware version knows what about the identity of a lens mounted, but surely Lightroom and other sofware cannot tell some Pentax lenses and some Sigma lenses apart from each other.
06-09-2012, 09:14 PM   #22
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QuoteOriginally posted by Class A Quote
I do not believe Pentax would resort to such malicious tactics.
I'm sure the tactics aren't malicious. Pentax isn't Apple, after all

I suspect that Pentax is just better able to make use of the information supplied by the lens and recorded in the metadata in more complex ways than 3rd party lens makers have been able to figure out. Pentax engineers naturally are more likely to spend time tuning their bodies to work well with their lenses - not only to make sure auto exposure works best, but for stuff like getting the the CA and distortion correction that some Pentax bodies like the K-x/K5 etc have built into them to work as well.

In-brand customisation or brand specific 'secret sauce' happens everywhere - eg Nikon and Canon are said to encrypt some data encoded in their RAW's, and obfuscate some of their metadata, making it hard to reverse engineer what is going on between body, lens and camera output.

QuoteOriginally posted by Class A Quote
Sometimes the camera may not even have a way of knowing whether the lens is third-party or not.
Indeed. While there are some pretty comprehensive lists of Pentax lens type metadata in the public domain, and while Pentax may have other ways of ensuring reliable detection of the lens type that is mounted, one could certainly forgive the camera for not judging properly what lens it has mounted, especially if it is an older model of camera or has older firmware.
06-09-2012, 09:39 PM   #23
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QuoteOriginally posted by rawr Quote
I suspect that Pentax is just better able to make use of the information supplied by the lens and recorded in the metadata in more complex ways than 3rd party lens makers have been able to figure out.
The metering is done by the camera. The metering chip sits at one of the faces of the pentaprism. The lens' role is just to provide the image. Therefore, Pentax lenses and third-party lenses are exactly in the same boat as far as metering is concerned.

The only hurdle is to make the camera believe that the lens is fit for use with matrix metering, i.e., the lens must be able to tell the camera its aperture range, etc.

QuoteOriginally posted by rawr Quote
In-brand customisation or brand specific 'secret sauce' happens everywhere - eg Nikon and Canon are said to encrypt some data encoded in their RAW's, and obfuscate some of their metadata, making it hard to reverse engineer what is going on between body, lens and camera output.
Nikon tried to encrypt the white balance value in their RAW files once, but it caused such an uproar that Nikon eventually gave in.

In principle you are right, though, and lens communication protocols are proprietary. I once read that Sigma reverse-engineers the protocols without paying license fees to Pentax. I have no idea whether this is true, but in any event Sigma is successful in making their lenses work on Pentax bodies, even including lens-based focusing.

06-10-2012, 12:56 AM   #24
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QuoteOriginally posted by Class A Quote
The lens role is just to provide the image. Therefore, Pentax lenses and third-party lenses are exactly in the same boat as far as metering is concerned.
'Exactly the same boat' may be too emphatic.

While in the K7/K-5 all 77 metering segments may receive a light value (irrespective of what AE exposure mode is employed and the lens employed), getting the light to the AE sensor is just the first step.

Judging the exposure will be influenced by the camera's understanding of user settings (EV compensation, custom image settings, flash usage, ISO setting, AE exposure mode selected etc), as well as (it would be reasonable to assume) the camera's knowledge of the optical properties of the lens attached (certainly in the case of Pentax lenses) and perhaps other data provided to the camera by the lens too.

So I still believe that somewhere in the calculation process Pentax lenses are likely to meter better than 3rd party lenses, especially when it comes to complex AE metering forms like matrix. I like my Sigmas, Tamron's, Ricoh's and other lenses a lot, but somehow Pentax lenses just meter better for me (except for my K and M lenses, unsurprisingly).
06-10-2012, 03:26 AM   #25
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After covering my required range (18-55 and 55-300) for my first dSLR (K10D), I added a fast lens and a flash. I already had an old flash (Metz 45 CT1) from my Minolta X700 days but lack of AF assist was the reason for me to add a new flash. The K-x also lacks AF assist and that would make me go for the flash before the lenses.

Regarding make and type, if you want to stick to pTTL and / or full manual, it does not matter to much but the more power, the better. Else I would opt for the Metz58. Everything the AF540 offers and a bit more from what I have read.

For on-camera use (as most people start), I suggest a flash with tilt-and-swivel head (so the AF360 would not be an option for me).

QuoteOriginally posted by mikemike Quote
The thought crossed my mind to sell or trade the 21 mm for one of those zoom lenses (to make my wife happy) and get the flash too, but that thought got all the way across my mind and the 21 isn't going anywhere .
Why don't you let your wife use the kit lens? Problem solved
06-10-2012, 03:58 AM   #26
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I would suggest Sigma 24-60/2.8. You can buy it used for order of USD 250. It is a bit wider than Tamron on the wide end and a little bit less wide than DA 21. Kind of sits in between, so to say. I transitioned from Tamron 28-75/2.8 to Sigma as I wanted wider lens. Then I went to DA* 16-50/2.8 while Sigma became my backup zoom and primary zoom for my daughter. It has added benefit of being full frame lens just in case Pentax comes about and around :-). You can find my mini-review with samples of Sigma here: Pentax Ways: Sigma EX 24-60/2.8 DG - mini review and samples

I chose it over Tamron because:
1. It is slightly wider
2. The OOF rendering seemed a bit smoother to me

Also to notice:
1. Tamron seems to have a bit punchier colors and higher contrast which is something you may or may not like. I'd rather prefer more gentleness here.
2. Tamron rotates in the same direction as other Pentax lenses while Sigma rotates the other way around.
3. Sigma seems to have ever so slightly better build.

Having said that, I've been shooting with Tamron for like 5 years and it is truly a stellar performer.
06-10-2012, 05:40 AM   #27
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Regarding the metering of various lenses, I once walked around the interior of my house and metered various scenes with sequentially spot, CW and matrix. this was with a K20 at the time. There was often a big difference between spot and the other modes, but very little diff. between CW and matrix. I'll just throw that out there in case anyone else has tried something similar.
06-10-2012, 08:05 AM   #28
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QuoteOriginally posted by rawr Quote
...as well as (it would be reasonable to assume) the camera's knowledge of the optical properties of the lens attached...
The camera does not know and does not need to know the optical properties of the lens in order to use matrix metering.

QuoteOriginally posted by rawr Quote
So I still believe that somewhere in the calculation process Pentax lenses are likely to meter better than 3rd party lenses, especially when it comes to complex AE metering forms like matrix.
You are of course entitled to your opinion, but I am sure that -- when systematically evaluated -- "better metering" is not an advantage of Pentax lenses over third-party lenses.
06-10-2012, 09:47 AM   #29
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QuoteOriginally posted by mikemike Quote
I had considered the Sigma 17-70 but from the photozone.de reviews for both 17-70s, it seems the pentax is superior in every almost respect.
I've seen side by side photo of the sigma and pentax 17-70 and both are very respectable, the colour and contrast of the pentax is better but for the rest there was little to no difference.


the photo
http://www.pentaxforum.nl/smf/index.php?topic=24351.0

Last edited by Anvh; 06-10-2012 at 01:32 PM.
06-10-2012, 11:50 AM   #30
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QuoteOriginally posted by Class A Quote
The camera does not know and does not need to know the optical properties of the lens in order to use matrix metering.
That information may not be a pre-condition for using matrix (or any other metering mode), but the camera may still take advantage of lens info.

If the firmware has knowledge of the optical properties of a particular Pentax lens (and there is every reason to believe that the firmware maintains such a database for CA and optical correction), why would it discard any of that information when it comes to making an accurate exposure?

I can certainly imagine, for example, knowledge of the vignetting and Tstop properties of a lens could help the camera very much in getting the exposure right when processing in-camera JPEGs. In the same way that this knowledge assists software tools like DxO in getting the exposure correct too.
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