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08-19-2010, 03:21 PM   #1
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3rd party lens compatibility with K7

Hi, seeking some advice as I'm new to Pentax and DSLR, previously had SLR film camera's and simple digital camera.

Can anybody comment on their experience using a Tamron 17-50, f2.8 with the K7, reading through the manual I discovered that alot of features offered by the K7 are not available when not using a genuine Pentax lens?

Not much I can do about it now as I've purchased the lens, but I may have changed my lens choice should I have known this previously. Searched alot of forums etc and nowhere did I see this raised as an issue.

Am I doing something wrong or is there sme software changes I can make? doesn't make sense that a lens should effects teh camera's ability to perform some focus features.

Thanks for any advice/help -- great site, very informative

08-19-2010, 03:31 PM   #2
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QuoteOriginally posted by Rush Quote
Hi, seeking some advice as I'm new to Pentax and DSLR, previously had SLR film camera's and simple digital camera.

Can anybody comment on their experience using a Tamron 17-50, f2.8 with the K7, reading through the manual I discovered that alot of features offered by the K7 are not available when not using a genuine Pentax lens?

Not much I can do about it now as I've purchased the lens, but I may have changed my lens choice should I have known this previously. Searched alot of forums etc and nowhere did I see this raised as an issue.

Am I doing something wrong or is there sme software changes I can make? doesn't make sense that a lens should effects teh camera's ability to perform some focus features.

Thanks for any advice/help -- great site, very informative
As far as I know, the only functions that are unavailable are those that rely on a lens profile, i.e. in-camera distortion and CA correction. Everything else functions perfectly.

I've used the Tammy 17-50/2.8 on my K-7 extensively and it's a great combo.
08-19-2010, 04:23 PM   #3
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QuoteOriginally posted by deadwolfbones Quote
As far as I know, the only functions that are unavailable are those that rely on a lens profile, i.e. in-camera distortion and CA correction. Everything else functions perfectly.

I've used the Tammy 17-50/2.8 on my K-7 extensively and it's a great combo.
That is correct. Only new genuine Pentax lenses have the CA and distortion in-camera correction available. But as far as the Tamron lens goes, everything else should work, AF, Auto Apature, other in camera filters, bracketing, remote, etc....
08-19-2010, 05:16 PM   #4
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thanks for your replies, I tried to use the pre focus and then camera takes photo when subject comes into pre focus range? couldn't seem to get it to work.
The pentax manual also mentions that this function will not work on non-Pentax DA, DA*, FA etc lens.

Does this work for you?

Also does your 11 point auto focus, centre weighted focus, subject tracking focus and face recognition work? I thought the manual said that only single point focus will function on non-Pentax lens (default)?

Thanks for your comments, maybe I need to read/ experiment further.

08-19-2010, 06:11 PM   #5
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QuoteOriginally posted by Rush Quote
thanks for your replies, I tried to use the pre focus and then camera takes photo when subject comes into pre focus range? couldn't seem to get it to work.
The pentax manual also mentions that this function will not work on non-Pentax DA, DA*, FA etc lens.

Does this work for you?

Also does your 11 point auto focus, centre weighted focus, subject tracking focus and face recognition work? I thought the manual said that only single point focus will function on non-Pentax lens (default)?

Thanks for your comments, maybe I need to read/ experiment further.
The catch-in-focus option will work with DA, FA and manual lenses. Now I have only tired this with a pentax brand manual lens and it worked. I do not have any non-pentax manual lenses to try it.

I thought that the auto focus points will work with any AF lens but I just looked in my manual and it does in fact say what you pointed out. That the center single point focus will be enabled no matter the setting if using anything other than a Pentax lens (but this also includes Pentax K, M and A lenses).
08-20-2010, 09:59 AM - 1 Like   #6
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Note when the manual says certain functions are only available with DA or FA lenses, they don't really mean mean only Pentax lenses. They also mean all third party equivalents. That's true of virtually everything (like anything about focus, metering, exposure modes, or flash) with the single exception of the in-camera lens corrections for CA or distortion. As far as I know, that's the *only* thing where there is actually a difference between handling of Pentax lenses versus third party equivalents.

The catch-in-focus feature only works on manual focus lenses or lenses that have a switch that allows them to be put into MF mode while the camera itself remains in AF mode. That's no different for Pentax lenses than any other brand.
08-20-2010, 03:14 PM   #7
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You also have to make sure the catch in focus feature is turned on in the custom menu. The camera has to be on AF-S (otherwise it won't matter if the camera is in focus or not), and I believe, but could be wrong, that it only works with Center point focus. That said, it isn't the fastest way to take a photo but can be faster than plain AF. That is, you can probably determine close focus faster than the AF sensors in some cases. If you're hoping to prefocus and have an object passing by trip the shutter because it is suddenly in focus, you may find yourself disappointed. It works better when you are panning a subject or focusing along with the movement of the subject (a passing car for instance).

Catch in focus will work with ANY MF lens (K mount), lenses which by the way, do not transmit any info to the camera. Meaning, the camera doesn't know if it's a Pentax lens or not (Pentax M and Pentax K lenses, the Pentax A lenses will transmist Aperture info but that's it). With an AF lens, as noted, you have to be able to turn it into an MF lens. That can be done in two ways. DA* lenses have an AF/MF switch as do some other autofocus lenses. With regular AF lenses (the FA, F, DA types) you can press the Lens release button while holding down the shutter release and turning the focus ring. Holding down the lens release button disengages the AF drive. It will spin like crazy but you can use the focus trap.

08-21-2010, 02:11 PM   #8
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check exposure too!

you should check exposure acuracy. I have found that my tamron 28-75 F2.8 has a perminent exposure error, \

while exposure wide open is correct, the exposure drifts upward almost a full stop by F11.

this is true on both my K10|D and K7D.

this is just a precaution, but I always check a lens and exposure even if I keep the lens, and plot out exposure accuracy of each lens on each body I own to have as a guide and reference when I am out taking shots.

I use a block wall lit by sunlight / daylight and measure greyscale value as a function of aperture selected.

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