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10-17-2010, 02:40 PM   #46
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QuoteOriginally posted by jimH Quote
Well the lenses that I have used with the K10 are: M-50 f1.4, M-28 f3.5 and they both seem to do the same thing when it comes to exposure. I kind of misspoke when I said "One stop less exposure" when I meant one stop more exposure. The green button pretty consistently sets the exposure about on stop darker than I like, so I either open the lens one stop or set the shutter on stop slower than recommended by the "green button". With your camera you can do some experimenting, but whatever it does, it should be pretty consistent, so you should be able to work with that.
this is quite true wide open, but when you get stopped down past F4-5.6 they tend to over expose.

Test them out over the entire range, it is worth your while

03-19-2015, 04:49 AM   #47
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Hello,

Today morning the day is dull but there are nice sunny rays coming from the clouds over the river give a nice scene to shoot...

I use my K-500 with a 16-45mm Pentax lens in M mode and pressing the green button give me wrong metering (1/6000 shutter and F11 or more) ...

Pointing the camera to a darker scene and metering again values seems correct but returning to the original scene measure become wrong again and if shooting the picture naturally will be very dark ...

There any logical explanation to this beaviour? This could be a specific and variable issue with the lens type (16-45 isn't fast like that ;-)) ? There are any way to "adapt" / "calibrate" (not AF) the lens and the body ? The body have the last firmware ...

Thanks a lot

Last edited by art_oliver; 03-19-2015 at 04:56 AM.
03-19-2015, 07:13 AM   #48
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Isn't the 16-45mm a DA lens?
03-19-2015, 07:59 AM   #49
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Hi

Thanks for the answer ... I don't understand the relation between the lens type and what I describe.

I have other DA(L) lens and I don't experiment the issue.

Could you please clarify ?

03-19-2015, 08:07 AM   #50
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Artur, is it possible that the contacts on your lens are dirty? It's a long shot, I know, but stranger things have happened to me.
03-19-2015, 08:13 AM   #51
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Is your lens this one?

SMC Pentax-DA 16-45mm F4 Reviews - DA Zoom Lenses - Pentax Lens Reviews & Lens Database

AFAIK, the DA lens don't really need to use the green button to meter unless your camera allows you to chose that option.
03-19-2015, 08:13 AM   #52
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QuoteOriginally posted by art_oliver Quote
I don't understand the relation between the lens type and what I describe.
You should not be able to do stop-down metering with lenses lacking an aperture ring.

With your DA lens, pressing the green button in M mode sets the aperture and shutter speed according to the program line the same as if you were in P mode. The measurement should happen with the lens fully open. The lens should not stop down. The big question might be whether that exposure worked. If the sun was in the frame and the ISO were set high, that exposure may well have been correct.


Steve
03-19-2015, 10:57 AM   #53
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Hello Again,

@photolady95 => Yep this my lens ...

@CR => I'll check the contacts but I don't think this is the case.

@stevebrot => I don't think the exposure be the correct one (pls see below) ...

Thanks for your input ... usually in M mode I set the machine on, point to the subject ask for AF (press Shutter) when focused press green button to for the given ISO (fixed at 400 in the case) obtain the "best" shutter and aperture suggested by the the meter. Now in the "correct /suggested zone" for shutter and aperture I can change/play with it or play with EV and finally shot (without the need to rotating the knobs to reach the balance of the EV). This procedure works ok until I start using DA 16-45mm ...

As I said I don't understand for a "grey" day the machine suggest a shutter of 1/6000 and aperture of F11 or more
Why ??? There's not enought light!

I understand that, perhaps I can start using other mode than M to avoid the problem. I will try.
I like to use M mode even with lens that could be used in more "advanced" ones.
I believe M mode should works good with any kind of lens or am I wrong ?

Thanks once again.


Last edited by art_oliver; 03-19-2015 at 11:06 AM.
03-19-2015, 01:43 PM   #54
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QuoteOriginally posted by art_oliver Quote
I believe M mode should works good with any kind of lens or am I wrong ?
There is nothing wrong with your flow. Many users on this site do something similar. When used properly it should allow you fine control over your exposure. Why you got 1/6000s at f/11 and ISO 400 is anyone's guess. Such a reading (~21.5 EV(100)) is possible for spot reading off specular sunlit highlights and is at the upper end of the meter sensitivity for your camera but is beyond the range of the meter on your camera. The camera should have displayed something like 1/3000s, f/11, ISO 400 with the display blinking. If this behavior is repeatable, your camera is in need of service. If the light were any brighter, the display would have been blinking.

In regards to green button metering in M mode...Your assumption that you are using stop-down metering is incorrect. Stop-down metering requires that the f-number be set using the aperture ring.* Your DA-series lens does not have an aperture ring. That is not a bad thing, however, since stop-down metering on your camera is limited to center-weighted average and is not consistently accurate.


Steve

* Your camera uses open-aperture metering when the aperture is controlled by the e-dials. This is the preferred and most accurate mode on all Pentax dSLRs. When the aperture is controlled by a ring on the lens, open-aperture readings are not possible and stop-down metering is supported instead. What that means is that the meter reading is made when the lens is stopped down in a manner similar to that used on the 60s-vintage Spotmatic film camera. For almost all K-mount lenses this is limited to M-mode, is actuated with the green button or optical DOF preview (some models), and requires that aperture ring be enabled in the menu settings.

Last edited by stevebrot; 03-19-2015 at 02:51 PM. Reason: Assumed meter specs for K-3 rather than K-500
03-27-2015, 05:47 AM   #55
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Hello again,

At the end and after mis-considering a little the suggestion of Canada_Rockies to clean the contacts, I did it.

My camera have now a year and never suppose the contacts and also the metal ring where the lens attach to the body could be so dirty
since the machine when not in use is inside my bag ...
I clean everything with a dry cottonette.

Since then the reported issue never happen again ;-)

Thanks once again Canada_Rockies.

Happy Shooting

Last edited by art_oliver; 03-27-2015 at 07:04 AM.
03-27-2015, 09:39 AM   #56
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QuoteOriginally posted by art_oliver Quote
Hello again,

At the end and after mis-considering a little the suggestion of Canada_Rockies to clean the contacts, I did it.

My camera have now a year and never suppose the contacts and also the metal ring where the lens attach to the body could be so dirty
since the machine when not in use is inside my bag ...
I clean everything with a dry cottonette.

Since then the reported issue never happen again ;-)

Thanks once again Canada_Rockies.

Happy Shooting
I'm a computer geek. The first thing we check when something acts strangely is the contacts. I have one computer that is on the end of 50 feet (15m or so) of CAT5 cable. Every once in a while I have to clean the contacts at both ends. It doesn't help that there is some electrical interference from motors en route.

I'm glad I was able to help you. Enjoy the forum and your photography.
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