[pschlute]

I may be misunderstanding this or perhaps it was explained and I missed it but why is Spot metering being used? Spot metering can easily cause the problem being discussed.

He is using both spot and CW metering. Look at his pictures. Spot metering improves the exposure but not by much.

[matroxication]

I don't think its camera related since the issue is only with this lens . Also when tested indoor , the exposure is good across all apertures. Hence not sure what is different with outdoor in bright light situation

---------- Post added 07-15-18 at 02:32 PM ----------

Came across the below thread and looks like Stone G has similar issue with different lens

Overexposure with Manual Lenses - PentaxForums.com

Everything seems fine with artificial lights

[pschlute]

Came across the below thread and looks like Stone G has similar issue with different lens

That thread is an old one and is related to the well documented problem that started with the K10D. Pentax switched to a completely new design of focus screen and that caused metering inaccuracies with manual lenses. I experienced it myself with the K10D. Some lenses were worse than others and it generally manifested itself as a progressive severe overexposure as the lens was stopped down and metered with the green button.

My K1 does not have this problem at all with any manual lens. I have tried the very same lens you have a problem with in both indoor, outdoor ant high contrast scenes, and cannot replicate your problem. As you have only experienced problems with one lens and not your 50mm I can only suggest the lens is at fault.

[matroxication]

Further testing at 2.8, 11 and 22. All were taken with spot metering.

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Last edited by matroxication; 08-25-2018 at 02:24 AM.

[monochrome]

Not my experience. That being said, things may be different in K-1 land. Are you saying that you get different shutter speeds from a manual aperture in Av mode than with green button in M mode with the same lens and settings. I get the same numbers on my K-3 in both modes and those numbers agree well with my handheld meters. I too always have one in the bag, but seldom have to consult it if metering in live view.

As for the liveview histogram. There is another recent thread where its deficiencies are plumbed in detail. The short story is that it represents the rear display characteristics and may not reflect an actual exposure or even the review mode histogram. One should expect it to be worthless with a manual aperture lens.


Steve

(...shoots a healthy mix of non-A K-mount and M42 lenses...)

RE: K-1 shutter speed issue above (and I can only read your end of the exchange) my experience with manual lenses on K-1 generally does not match the Poster’s.


*uses DoF Preview metering in M Mode or a handheld incident, reflective or Zone V Spot meter for careful, precise metering.




Re

[matroxication]

Tried the DoF preview metering as well earlier but no luck. I tested the SMC 50 1.4 and I do not have this issue with that lens. The exposure was spot on.

[stevebrot]

Further testing at 2.8, 11 and 22. All were taken with spot metering.

There is a fault with the lens. All three exposures represent close to the same EV(100) and should have resulted in very similar images.

#1

f/2.8, 1/4000s, ISO 100 => EV 15.0

#2

f/11, 1/400s, ISO 100 => EV 15.7

#3

f/22, 1/100s ISO 100 => EV 15.7

Chances are very good to excellent that your lens has a lazy aperture mechanism that is slow to stop down. A repeat trial using the same EV for each aperture (see table at: https://en.wikipedia.org/wiki/Exposure_value#EV_as_an_indicator_of_camera_settings) with meter for the f/2.8 exposure only should prove the source. Question...did you check that aperture operation is snappy (use finger flick of the lever) at all aperture ring positions, particularly at f/11, f/16, and f/22?


Steve

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Last edited by stevebrot; 07-15-2018 at 04:46 PM.

[matroxication]

Thanks Steve and everyone for the support. Its lot of valuable information that I have learned about using the manual lenses.

The seller was understandable and was happy to provide the refund and hence am sending this lens back to him.

Now am back to square one in finding a wide angle lens

[baro-nite]

Good for the seller to give you a refund. My replacement for this lens was the A-series equivalent, which is the same optical formula, and of course then you get auto-exposure functionality. It's one of my favorites.

[MJKoski]

Now am back to square one in finding a wide angle lens

Have a look for Zeiss 25/2.8 .ZK. I am getting one soon to fix a missing focal length between 15mm and 35mm.

[pinholecam]

Mine isn't far off, usually +1 stop and that might even be just what the camera 'thinks' is better exposure compared to my needs.

Try this (which I practice ).
1. Block out stray light from the eye piece (eg. by using the thumb ), obviously if you are hand holding, the eye already blocks it off.
2. If you are constantly using a f-stop value (eg f11), you can just set a metering bias by setting the exposure compensation in M mode.
So in my case, if my K24/2.8 is always for landscapes and shot at f11 and I know its always +1ev off, I just set the -1ev compensation, hence and green button metering from then onwards will offset accordingly.


All said, if its +5ev off, maybe its a slow aperture that you have...

[SirTomster]

Great info to know.

I hope to buy a lot of old glass and will make sure to do some testing like this. Better to find out early then when you are on site and want to use the piece in question.