Why my photos are under exposed when i use the Pentax-DA 16-85 mm lens

NickTent · 02-19-2023, 09:51 AM

Hello,
I have noticed that all photos taken with .y Pentax-DA 16-85mm are significant under exposed, even though the camera metering shows that the exposure is fine. I use a Pentax K-S2 camera. I have tried the AUTO, Aperrture priority, Manual and it is consistently significant under exposed. Same camera settings with a different lens are fine! Anyone can help me resolve this issue? It is something new, the Pentax-DA 16-85mm has alawys worked fine for me. What am I missing?

Thank you,

Nick

aaacb · 02-19-2023, 10:53 AM

If it's more at smaller apertures (say f11), then it could be a slow aperture. Are the other lenses auto aperture? If not, it could also be aperture lever failure in the camera.

**ramseybuckeye** · 02-19-2023, 04:19 PM

I don't know for sure that it could cause it, but I would clean the contacts on the lens to make sure your not losing connection during the process. If possible I would shine a light into the lens and take photos of it when you are at different stops, and compare to another lens.

**Bob 256** · 02-19-2023, 07:56 PM

Check the two tabs which stick up from the lens. One is stationary and anchored to the lens with a sloped edge on one side. The other is moveable and is used by the camera to hold the iris open at the correct f-stop. Is the moveable one possibly bent or damaged? While you have the lens off the camera, look through it from the rear. Make sure that pulling the right tab (the moveable one) toward you (while it's on the right and the top of the lens faces away from you). It should move easily and you should see the iris open all the way when the tab is pulled full downwards.

Also make sure your lens is in AUTO (aperture ring) and not set on a specific f-stop.

Attached Images

**Terry C** · 02-20-2023, 01:21 AM

Do you vary the exposure points according to the focal length used ? I use this lens often and find that it works best with full matrix at the wide end, and single point at the long end.

steephill · 02-20-2023, 04:57 AM

What is your other lens which works fine? It could be aperture block failure.

Jonathan Mac · 02-20-2023, 08:05 AM - **1 Like**

Originally posted by aaacb

If it's more at smaller apertures (say f11), then it could be a slow aperture. Are the other lenses auto aperture? If not, it could also be aperture lever failure in the camera.

I would expect a slow aperture to produce over-exposed shots, not the reverse, as it wouldn't have finished closing to the desired aperture setting when the image was taken.

Aperture block failure is a likely cause but not if only one lens is affected.

I have found my 16-85mm to give the most accurate exposure of any of any lens on my K-3.

NickTent · 02-21-2023, 05:10 AM

Hello,

thank you all for your replies\suggestions. So far what I found is that if I turned on and use , once, the bult in flash and then turn it off, then the rest of the photos are coming out properly exposed. The other lens I used is: HD Pentax-DA 55-300mm F4.5-6.3 PLM WR RE. With this lens, if I replace the 16-85mm with this one and change nothing on the camera, the photos are properly exposed.!

Thank you again,

Nick

normhead · 02-21-2023, 06:34 AM

Originally posted by NickTent

So far what I found is that if I turned on and use , once, the bult in flash and then turn it off, then the rest of the photos are coming out properly exposed.

Now that's jut weird. I was going to suggest using the EV dial to adjust exposure, but that works better.

NickTent · 02-21-2023, 10:13 AM

Hello,

I have an update on this issue. Now I feel it is a camera issue. I have replaced the 16-85mm lens with :

Pentax smc FA 31 mm f/1.8 AL

and

Pentax smc D-FA 100mm F2.8 Macro WR Specs

The issue happens with both these lenses. I also tried the flash on and off but the issue continues. I have used EV+3 stops and then is when the images seems to be proper exposed. Strangest thing is that the issue does not happen when I use :

HD Pentax-DA 55-300mm F4.5-6.3 PLM WR RE

I was wondering if there is hard reset for the K-S2 camera. I have already done the reset using the menu but no changes. Anyone knows how to hardware reset the K-S2? Not sure what else to try.

Thank you,

Nick

---------- Post added 02-21-23 at 10:33 AM ----------

The Iris is opening when I pull down the lever on the lense. there is no apertrure setting on the lens. It seems that the camera consistently under exposures for 3 stops. Looks the images appear proper when I use a EV+3!

**ehrwien** · 02-21-2023, 01:36 PM

It doesn't happen with the 55-300 PLM because that one is KAF4 and the aperture in that lens is controlled electronically.

Unfortunately I'll say this very much looks like the known aperture / solenoid failure in the camera. See the stickied thread in this subforum for your options.

Jonathan Mac · 02-22-2023, 07:36 AM

Originally posted by ehrwien

It doesn't happen with the 55-300 PLM because that one is KAF4 and the aperture in that lens is controlled electronically.

Unfortunately I'll say this very much looks like the known aperture / solenoid failure in the camera. See the stickied thread in this subforum for your options.

What I was about to say - the difference is the KAF4 mount that has no mechanical aperture connection to the camera - it's done electronically.

TonyMaris · 06-12-2023, 08:00 AM

Originally posted by NickTent

Hello,
I have noticed that all photos taken with .y Pentax-DA 16-85mm are significant under exposed, even though the camera metering shows that the exposure is fine. I use a Pentax K-S2 camera. I have tried the AUTO, Aperrture priority, Manual and it is consistently significant under exposed. Same camera settings with a different lens are fine! Anyone can help me resolve this issue? It is something new, the Pentax-DA 16-85mm has alawys worked fine for me. What am I missing?

Thank you,

Nick

I’ll be interested to see any answers! Mine has EXACTLY the same issue… with the same OE lens.

I also use a simpler Pentax DA 55mm-300mm lens and it was fine with that 2 weeks ago but that has now gone the same way !…. With the OE lens, I reckon I’m at least 5 stops underexposed.
I’ve been trying to sort it this afternoon but, the only way to get a correctly exposed shot is to use the ‘B’ setting. It took 2.7secs at F4, ISO100, for a shot that should have been around 1/40th @F4.

UPDATE: I’ve now discovered if I use ‘Live View’ as opposed to ‘viewfinder’ it’s okay!
2 identical shots:
Viewfinder, 1/25th F4.0 ISO 400, UNDEREXPOSED.
LiveView, 1.3secs F4.0 ISO 400. CORRECTLY EXPOSED.

What’s going on? 🧐🥴

TonyMaris · 06-16-2023, 11:09 AM

Today, I’ve had chance to compare shot .with 2 bodies (a K-s2 and a a K20D) and 3 lenses.

This eliminates any fault on any of the lenses. What I’ve discovered is well exposed images with all lenses on my old K20D. With the K-s2, if used on “LiveView” all images are correctly exposed. However, used with the viewfinder, regardless of lens fitted, all are vastly underexposed even though it gives the correct exposure readings!

Now to find out why…. ��

**photogem** · 06-16-2023, 10:37 PM

It should be very clear:

The DA55-300PLM is a KAF4 lens and thus the aperture-control through the solenoid is not needed and thus not in action.

This is the test to find out it is ABF:
How to detect aperture block failure on Pentax K-S1 (and K-S2) - PentaxForums.com

and as the FA31ltd and the D-FA100macro also don't work, it is with 99,9% certainty ABF and thus:
Manual: Solenoid replacement: Pentax K-S2 (and K-70) - PentaxForums.com

02-19-2023, 09:51 AM	#1
NickTent Junior Member Join Date: Mar 2018 Posts: 46	Why my photos are under exposed when i use the Pentax-DA 16-85 mm lens Hello, I have noticed that all photos taken with .y Pentax-DA 16-85mm are significant under exposed, even though the camera metering shows that the exposure is fine. I use a Pentax K-S2 camera. I have tried the AUTO, Aperrture priority, Manual and it is consistently significant under exposed. Same camera settings with a different lens are fine! Anyone can help me resolve this issue? It is something new, the Pentax-DA 16-85mm has alawys worked fine for me. What am I missing? Thank you, Nick

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02-19-2023, 10:53 AM	#2
aaacb Pentaxian Join Date: May 2016 Photos: Gallery Posts: 3,725	If it's more at smaller apertures (say f11), then it could be a slow aperture. Are the other lenses auto aperture? If not, it could also be aperture lever failure in the camera.

02-19-2023, 04:19 PM	#3
ramseybuckeye Site Supporter Join Date: Apr 2009 Location: Hampstead, NC Photos: Gallery Posts: 17,292	I don't know for sure that it could cause it, but I would clean the contacts on the lens to make sure your not losing connection during the process. If possible I would shine a light into the lens and take photos of it when you are at different stops, and compare to another lens.

02-19-2023, 07:56 PM	#4
Bob 256 Site Supporter Join Date: Jun 2008 Location: Idaho Photos: Gallery Posts: 2,375	Check the two tabs which stick up from the lens. One is stationary and anchored to the lens with a sloped edge on one side. The other is moveable and is used by the camera to hold the iris open at the correct f-stop. Is the moveable one possibly bent or damaged? While you have the lens off the camera, look through it from the rear. Make sure that pulling the right tab (the moveable one) toward you (while it's on the right and the top of the lens faces away from you). It should move easily and you should see the iris open all the way when the tab is pulled full downwards. Also make sure your lens is in AUTO (aperture ring) and not set on a specific f-stop. Attached Images

02-20-2023, 01:21 AM	#5
Terry C Site Supporter Join Date: Dec 2016 Location: North west Tasmania. Photos: Gallery Posts: 609	Do you vary the exposure points according to the focal length used ? I use this lens often and find that it works best with full matrix at the wide end, and single point at the long end.

02-20-2023, 04:57 AM	#6
steephill Pentaxian Join Date: Nov 2018 Photos: Gallery Posts: 585	What is your other lens which works fine? It could be aperture block failure.

02-20-2023, 08:05 AM - 1 Like	#7
Jonathan Mac Pentaxian Join Date: Apr 2009 Location: Madrid, Spain Posts: 10,897	Originally posted by aaacb If it's more at smaller apertures (say f11), then it could be a slow aperture. Are the other lenses auto aperture? If not, it could also be aperture lever failure in the camera. I would expect a slow aperture to produce over-exposed shots, not the reverse, as it wouldn't have finished closing to the desired aperture setting when the image was taken. Aperture block failure is a likely cause but not if only one lens is affected. I have found my 16-85mm to give the most accurate exposure of any of any lens on my K-3.

02-21-2023, 05:10 AM	#8
NickTent Junior Member Join Date: Mar 2018 Posts: 46 Original Poster	Hello, thank you all for your replies\suggestions. So far what I found is that if I turned on and use , once, the bult in flash and then turn it off, then the rest of the photos are coming out properly exposed. The other lens I used is: HD Pentax-DA 55-300mm F4.5-6.3 PLM WR RE. With this lens, if I replace the 16-85mm with this one and change nothing on the camera, the photos are properly exposed.! Thank you again, Nick

02-21-2023, 06:34 AM	#9
normhead Pentaxian Join Date: Jun 2007 Location: Near Algonquin Park Photos: Gallery \| Albums Posts: 40,451	Originally posted by NickTent So far what I found is that if I turned on and use , once, the bult in flash and then turn it off, then the rest of the photos are coming out properly exposed. Now that's jut weird. I was going to suggest using the EV dial to adjust exposure, but that works better.

02-21-2023, 10:13 AM	#10
NickTent Junior Member Join Date: Mar 2018 Posts: 46 Original Poster	Hello, I have an update on this issue. Now I feel it is a camera issue. I have replaced the 16-85mm lens with : Pentax smc FA 31 mm f/1.8 AL and Pentax smc D-FA 100mm F2.8 Macro WR Specs The issue happens with both these lenses. I also tried the flash on and off but the issue continues. I have used EV+3 stops and then is when the images seems to be proper exposed. Strangest thing is that the issue does not happen when I use : HD Pentax-DA 55-300mm F4.5-6.3 PLM WR RE I was wondering if there is hard reset for the K-S2 camera. I have already done the reset using the menu but no changes. Anyone knows how to hardware reset the K-S2? Not sure what else to try. Thank you, Nick ---------- Post added 02-21-23 at 10:33 AM ---------- The Iris is opening when I pull down the lever on the lense. there is no apertrure setting on the lens. It seems that the camera consistently under exposures for 3 stops. Looks the images appear proper when I use a EV+3!

02-21-2023, 01:36 PM	#11
ehrwien Site Supporter Join Date: May 2016 Posts: 2,782	It doesn't happen with the 55-300 PLM because that one is KAF4 and the aperture in that lens is controlled electronically. Unfortunately I'll say this very much looks like the known aperture / solenoid failure in the camera. See the stickied thread in this subforum for your options.

02-22-2023, 07:36 AM	#12
Jonathan Mac Pentaxian Join Date: Apr 2009 Location: Madrid, Spain Posts: 10,897	Originally posted by ehrwien It doesn't happen with the 55-300 PLM because that one is KAF4 and the aperture in that lens is controlled electronically. Unfortunately I'll say this very much looks like the known aperture / solenoid failure in the camera. See the stickied thread in this subforum for your options. What I was about to say - the difference is the KAF4 mount that has no mechanical aperture connection to the camera - it's done electronically.

06-12-2023, 08:00 AM	#13
TonyMaris New Member Join Date: Apr 2009 Location: South Lincs. UK. Posts: 3	Originally posted by NickTent Hello, I have noticed that all photos taken with .y Pentax-DA 16-85mm are significant under exposed, even though the camera metering shows that the exposure is fine. I use a Pentax K-S2 camera. I have tried the AUTO, Aperrture priority, Manual and it is consistently significant under exposed. Same camera settings with a different lens are fine! Anyone can help me resolve this issue? It is something new, the Pentax-DA 16-85mm has alawys worked fine for me. What am I missing? Thank you, Nick I’ll be interested to see any answers! Mine has EXACTLY the same issue… with the same OE lens. I also use a simpler Pentax DA 55mm-300mm lens and it was fine with that 2 weeks ago but that has now gone the same way !…. With the OE lens, I reckon I’m at least 5 stops underexposed. I’ve been trying to sort it this afternoon but, the only way to get a correctly exposed shot is to use the ‘B’ setting. It took 2.7secs at F4, ISO100, for a shot that should have been around 1/40th @F4. UPDATE: I’ve now discovered if I use ‘Live View’ as opposed to ‘viewfinder’ it’s okay! 2 identical shots: Viewfinder, 1/25th F4.0 ISO 400, UNDEREXPOSED. LiveView, 1.3secs F4.0 ISO 400. CORRECTLY EXPOSED. What’s going on? 🧐🥴

06-16-2023, 11:09 AM	#14
TonyMaris New Member Join Date: Apr 2009 Location: South Lincs. UK. Posts: 3	Today, I’ve had chance to compare shot .with 2 bodies (a K-s2 and a a K20D) and 3 lenses. This eliminates any fault on any of the lenses. What I’ve discovered is well exposed images with all lenses on my old K20D. With the K-s2, if used on “LiveView” all images are correctly exposed. However, used with the viewfinder, regardless of lens fitted, all are vastly underexposed even though it gives the correct exposure readings! Now to find out why…. ��

06-16-2023, 10:37 PM	#15
photogem Site Supporter Join Date: Apr 2015 Posts: 3,520	It should be very clear: The DA55-300PLM is a KAF4 lens and thus the aperture-control through the solenoid is not needed and thus not in action. This is the test to find out it is ABF: How to detect aperture block failure on Pentax K-S1 (and K-S2) - PentaxForums.com and as the FA31ltd and the D-FA100macro also don't work, it is with 99,9% certainty ABF and thus: Manual: Solenoid replacement: Pentax K-S2 (and K-70) - PentaxForums.com