Pentax K-1 Auto ISO 200

**jeffshaddix** · 03-06-2021, 02:19 PM

Does anyone know why the K-1 tends to use ISO 200 over 100 when in Av-priority and using auto-ISO? It's not due to auto-ISO speed; it could be measuring a 1/2000 shutter speed and still choose ISO 200 over 100. This was not the case for my K-7, K-5, and K-5iis.

Cheers!

**Michail_P** · 03-06-2021, 02:21 PM

I also encounter this with my K-70. Not that annoying but I’d love to know why.

stevebrot · 03-06-2021, 02:33 PM - **2 Likes**

Originally posted by jeffshaddix

Does anyone know why the K-1 tends to use ISO 200 over 100 when in Av-priority

The quick answer is that auto-ISO does not ramp in a predictable way, regardless of how it is set up.* IIRC, it is very difficult to force to ISO 100 in Av mode and somewhat easier in Tv mode (hint...hint...).

Do you have highlight or shadow correction enabled? (Sorry, can't remember which one.) Strange things also happen with bracketing and exposure compensation.

Steve

(...is of the opinion that auto-ISO is an invention of the Devil and evil...)

* Unless one considers TAv mode to be auto-ISO.

kastasir · 03-06-2021, 02:50 PM

K70 Highlight

Attached Images

**ehrwien** · 03-06-2021, 03:12 PM - **2 Likes**

I've encountered that issue with my K-S2 with Highlight or Shadow Protection enabled. I've turned those off ever since and underexpose by 2/3 of a stop most of the time with most lenses, no issue for me since I like to take the time to process the RAW files afterwards anyways. But in changing lighting conditions I have to see and think for myself to adapt accordingly, so sometimes I make use of more or less exposure compensation. Maybe I should try those modes for a while to see if it can help me prevent some mishaps in those situations for the cost of losing ISO 100?

C_Jones · 03-06-2021, 03:23 PM

Highlight Correction is not available at an ISO below 200. If the setting is present, the available ISO will be limited.

**jeffshaddix** · 03-06-2021, 05:22 PM

Hey guys, thanks for the responses.

~~I'm shooting RAW and highlight correction is off. It's not fixing to ISO 200, but fluctuates continuously between ISO 100 and 200 in normal outdoor (bright) shooting.~~ It was highlight correction after all, even though I was shooting RAW.

I actually like auto-ISO, but it could be improved. The perfect mode for me would be if I could set a minimum shutter speed on the front dial (still aperture on the back). Note this isn't TAv, because I want to specify minimum shutter speed, not a fixed shutter speed. I get around this currently but having U1, U2, and U3 set to AV auto-ISO slow, medium, and fast respectively, and then I swap as appropriate.

Back to the topic at hand. It could be that the K-1 sensor has some issues with highlights at ISO 100, and that's why I see it flicker between 100/200 walking outside.

Last edited by jeffshaddix; 03-07-2021 at 02:47 PM.

**jbinpg** · 03-06-2021, 06:27 PM

Sounds like the only way to guarantee ISO100 in an auto mode is to use the Sv mode.

**Michail_P** · 03-07-2021, 01:13 AM

Thanks for the responses. I guess I’ll try turning off highlight correction. But ISO200 is fine anyway.

biz-engineer · 03-07-2021, 01:21 AM - **2 Likes**

On the K1, if highlight protection is set to Auto or On, and ISO is set to auto-ISO, and there is a bright light in the scene detected by the exposure meter, the ISO setting won't go below 200.

**jeffshaddix** · 03-07-2021, 02:55 PM

Originally posted by biz-engineer

On the K1, if highlight protection is set to Auto or On, and ISO is set to auto-ISO, and there is a bright light in the scene detected by the exposure meter, the ISO setting won't go below 200.

So I went and checked again, and sure enough highlight correction was set to Auto. Turning it off fixed it to use ISO 100 unless it needs to go higher to maintain shutter speed. I did a little research, and it looks like highlight correction is trying to underexpose by lowering the ISO a bit versus the displayed exposure settings. I'd rather just use -2/3 EV exposure compensation with ISO 100.

stevebrot · 03-09-2021, 11:20 AM

Originally posted by jeffshaddix

The perfect mode for me would be if I could set a minimum shutter speed on the front dial (still aperture on the back).

You are not the first person to ask for that or a similar feature, the the obvious question might be expected behavior when there is a dead lock between max ISO and min shutter.

Steve

**jeffshaddix** · 03-10-2021, 08:03 AM

Originally posted by stevebrot

You are not the first person to ask for that or a similar feature, the the obvious question might be expected behavior when there is a dead lock between max ISO and min shutter.

Steve

Thanks for the thought provoking question.

I would say it should be similar to how TAv handles similar dead lock. If the scene is too dark for the TAv settings with ISO pegged, the settings in the viewfinder will blink and the image will be underexposed.

03-06-2021, 02:19 PM	#1
jeffshaddix Site Supporter Join Date: Jun 2010 Location: Colorado Posts: 1,473	Pentax K-1 Auto ISO 200 Does anyone know why the K-1 tends to use ISO 200 over 100 when in Av-priority and using auto-ISO? It's not due to auto-ISO speed; it could be measuring a 1/2000 shutter speed and still choose ISO 200 over 100. This was not the case for my K-7, K-5, and K-5iis. Cheers!

03-06-2021, 02:33 PM - 2 Likes	#3
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by jeffshaddix Does anyone know why the K-1 tends to use ISO 200 over 100 when in Av-priority The quick answer is that auto-ISO does not ramp in a predictable way, regardless of how it is set up.* IIRC, it is very difficult to force to ISO 100 in Av mode and somewhat easier in Tv mode (hint...hint...). Do you have highlight or shadow correction enabled? (Sorry, can't remember which one.) Strange things also happen with bracketing and exposure compensation. Steve (...is of the opinion that auto-ISO is an invention of the Devil and evil...) * Unless one considers TAv mode to be auto-ISO. Last edited by stevebrot; 03-06-2021 at 02:37 PM. Reason: Added hint

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
What maximum ISO to use on K-70 default auto ISO range?	OldChE	Pentax K-70 & KF	7	02-19-2018 08:01 PM
[K-S2] ISO no lower than 200 in Auto ISO (100-x)	ehrwien	Pentax K-S1 & K-S2	4	01-17-2018 03:09 PM
[Auto-ISO] so, is the K5 and Kr brave enough to use max iso?	Reportage	Pentax K-5 & K-5 II	13	10-24-2010 03:30 PM
Default ISO 200 vs ISO 100	joodiespost	Troubleshooting and Beginner Help	6	01-09-2010 05:50 PM
iso 100 or iso 200	kiwao	Pentax DSLR Discussion	8	03-05-2009 01:02 PM

03-06-2021, 02:21 PM	#2
Michail_P Site Supporter Join Date: Nov 2019 Location: Kalymnos Photos: Gallery Posts: 3,006	I also encounter this with my K-70. Not that annoying but I’d love to know why.

03-06-2021, 02:50 PM	#4
kastasir Junior Member Join Date: Mar 2014 Posts: 25	K70 Highlight Attached Images

03-06-2021, 03:12 PM - 2 Likes	#5
ehrwien Site Supporter Join Date: May 2016 Posts: 2,784	I've encountered that issue with my K-S2 with Highlight or Shadow Protection enabled. I've turned those off ever since and underexpose by 2/3 of a stop most of the time with most lenses, no issue for me since I like to take the time to process the RAW files afterwards anyways. But in changing lighting conditions I have to see and think for myself to adapt accordingly, so sometimes I make use of more or less exposure compensation. Maybe I should try those modes for a while to see if it can help me prevent some mishaps in those situations for the cost of losing ISO 100?

03-06-2021, 03:23 PM	#6
C_Jones Pentaxian Join Date: Sep 2012 Location: NY Photos: Gallery \| Albums Posts: 6,086	Highlight Correction is not available at an ISO below 200. If the setting is present, the available ISO will be limited.

03-06-2021, 05:22 PM	#7
jeffshaddix Site Supporter Join Date: Jun 2010 Location: Colorado Posts: 1,473 Original Poster	Hey guys, thanks for the responses. ~~I'm shooting RAW and highlight correction is off. It's not fixing to ISO 200, but fluctuates continuously between ISO 100 and 200 in normal outdoor (bright) shooting.~~ It was highlight correction after all, even though I was shooting RAW. I actually like auto-ISO, but it could be improved. The perfect mode for me would be if I could set a minimum shutter speed on the front dial (still aperture on the back). Note this isn't TAv, because I want to specify minimum shutter speed, not a fixed shutter speed. I get around this currently but having U1, U2, and U3 set to AV auto-ISO slow, medium, and fast respectively, and then I swap as appropriate. Back to the topic at hand. It could be that the K-1 sensor has some issues with highlights at ISO 100, and that's why I see it flicker between 100/200 walking outside. Last edited by jeffshaddix; 03-07-2021 at 02:47 PM.

03-06-2021, 06:27 PM	#8
jbinpg Site Supporter Join Date: Mar 2008 Location: Prince George, BC Photos: Gallery \| Albums Posts: 3,546	Sounds like the only way to guarantee ISO100 in an auto mode is to use the Sv mode.

03-07-2021, 01:13 AM	#9
Michail_P Site Supporter Join Date: Nov 2019 Location: Kalymnos Photos: Gallery Posts: 3,006	Thanks for the responses. I guess I’ll try turning off highlight correction. But ISO200 is fine anyway.

03-07-2021, 01:21 AM - 2 Likes	#10
biz-engineer Pentaxian Join Date: Feb 2015 Photos: Gallery Posts: 12,249	On the K1, if *highlight protection* is set to *Auto* or On, and ISO is set to auto-ISO, and there is a bright light in the scene detected by the exposure meter, the ISO setting won't go below 200.

03-07-2021, 02:55 PM	#11
jeffshaddix Site Supporter Join Date: Jun 2010 Location: Colorado Posts: 1,473 Original Poster	Originally posted by biz-engineer On the K1, if *highlight protection* is set to *Auto* or On, and ISO is set to auto-ISO, and there is a bright light in the scene detected by the exposure meter, the ISO setting won't go below 200. So I went and checked again, and sure enough highlight correction was set to Auto. Turning it off fixed it to use ISO 100 unless it needs to go higher to maintain shutter speed. I did a little research, and it looks like highlight correction is trying to underexpose by lowering the ISO a bit versus the displayed exposure settings. I'd rather just use -2/3 EV exposure compensation with ISO 100.

03-09-2021, 11:20 AM	#12
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by jeffshaddix The perfect mode for me would be if I could set a minimum shutter speed on the front dial (still aperture on the back). You are not the first person to ask for that or a similar feature, the the obvious question might be expected behavior when there is a dead lock between max ISO and min shutter. Steve

03-10-2021, 08:03 AM	#13
jeffshaddix Site Supporter Join Date: Jun 2010 Location: Colorado Posts: 1,473 Original Poster	Originally posted by stevebrot You are not the first person to ask for that or a similar feature, the the obvious question might be expected behavior when there is a dead lock between max ISO and min shutter. Steve Thanks for the thought provoking question. I would say it should be similar to how TAv handles similar dead lock. If the scene is too dark for the TAv settings with ISO pegged, the settings in the viewfinder will blink and the image will be underexposed.