K-3 doesn't focus in low light conditions

zoolander · 10-28-2014, 02:32 AM

Hello all !

I just bought a new Pentax K-3 - woohoo ! But I tested out the low light focus ability in a dimly lit room, and it could not achieve focus on a gray bedspread and posts. I was using a Sigma 50mm 1.4, and also a Pentax FA 50mm 1.4, and both hunted. Only once did the Sigma get a lock. All at f/1.4.

I had it on the center focus point, then tried it on using all the focus points.

Does that sound right ? Its supposed to achieve focus in complete darkness, and this was a very dimly light room with the adjacent rooms light on. I was expecting it to achieve focus in complete darkness.

(Also my flu card doesn't work and the K-3 doesn't see the card in slot 2. But I'll make another thread for this)

Is this camera DOA ? Or am I doing something wrong(By the way, its an upgrade from my K-5, and its faster, sharper, stabler, quicker OS and snappier so I'm real happy ! )

Steve.Ledger · 10-28-2014, 02:39 AM

Originally posted by zoolander

Its supposed to achieve focus in complete darkness

Seriously?

RollsUp · 10-28-2014, 02:41 AM

Have you updated the firmware for both the K-3 and the Flucard?

asp1880 · 10-28-2014, 02:42 AM

Two things:
1. The camera needs some contrast (lines, structure, pattern) to be able to focus. You can't expect it to focus on a featureless surface such as the clear blue sky, light or no light. Gray bedspread - that sounds a bit low contrast to me.
2. It's not supposed to achieve focus in complete darkness. It's spec'ed to work down to light level EV -3, which is equivalent to 1/2 second at f/1.4 and ISO 3200. Try some manual settings to work out which exposure renders the grey bedspread as midtone, and that's your light level.
3. These experiments are only interesting with the focus assist lamp disabled.

Regards,
--Anders.

rawr · 10-28-2014, 02:52 AM

The K-3 can certainly do it's job in very low-light.

To test low-light AF, find a contrasty focus target, confirm focus in bright light, then dim the lights progressively until the AF stops working.

You may find this useful BTW, from the Nikon D4 manual:

zoolander · 10-28-2014, 03:12 AM

Originally posted by Steve.Ledger

Seriously?

I thought -3EV was complete darkness. Thats what people have been banging on about.

---------- Post added 10-28-14 at 08:14 PM ----------

Originally posted by RollsUp

Have you updated the firmware for both the K-3 and the Flucard?

The K-3 is the Prestige edition and comes with the latest firmware - I checked it already.

Adam cleared up the flucard for me on the other thread. The camera was bundled with an 8gb card which is not the original Pentax 16gb flucard, so I can only share photos and not have the tethering, which is a real bummer.

---------- Post added 10-28-14 at 08:18 PM ----------

Originally posted by asp1880

Two things:
1. The camera needs some contrast (lines, structure, pattern) to be able to focus. You can't expect it to focus on a featureless surface such as the clear blue sky, light or no light. Gray bedspread - that sounds a bit low contrast to me.
2. It's not supposed to achieve focus in complete darkness. It's spec'ed to work down to light level EV -3, which is equivalent to 1/2 second at f/1.4 and ISO 3200. Try some manual settings to work out which exposure renders the grey bedspread as midtone, and that's your light level.
3. These experiments are only interesting with the focus assist lamp disabled.

Regards,
--Anders.

Thats exactly what I thought !

I was in AF.S, so I tried AF.C, and bingo ! AF points are lighting up and its hitting focus on the bedspread, and anything I like and even darker spots ! In total darkness its not metering the picture but it is achieving focus in AF.C.

Thanks

---------- Post added 10-28-14 at 08:20 PM ----------

Originally posted by rawr

The K-3 can certainly do it's job in very low-light.

To test low-light AF, find a contrasty focus target, confirm focus in bright light, then dim the lights progressively until the AF stops working.

You may find this useful BTW, from the Nikon D4 manual:

Thanks, I'll keep that all in mind.

Gotta love this forum !

stevebrot · 10-28-2014, 07:34 AM

Originally posted by zoolander

I thought -3EV was complete darkness. Thats what people have been banging on about.

No, -3 EV is not complete darkness, but it is dim enough that you probably would not be able to make your way without stumbling over something.

Originally posted by zoolander

In total darkness its not metering the picture but it is achieving focus in AF.C.

It may have taken the photo in AF-C, but neither that nor the focus point lights in the viewfinder are evidence of acquired focus.

AF-C with default settings will allow shutter release before focus is acquired
The red focus point indicators merely show which point the camera is using
Focus acquisition is signaled by the green hexagon at the bottom of the viewfinder display along with a beep

Steve

ogl · 10-28-2014, 08:46 AM

Originally posted by zoolander

I thought -3EV was complete darkness.

Gotta love this forum !

Exposure value - Wikipedia, the free encyclopedia

Exposure times - 15 sec for f1.4 and EV-3. You need tripod to make photos in such condition.

EV
TYPE OF LIGHTING SITUATION
-6
Night, away from city lights, subject under starlight only.
-5
Night, away from city lights, subject under crescent moon.
-4
Night, away from city lights, subject under half moon. Meteors (during showers, with time exposure).
-3
Night, away from city lights, subject under full moon

aleonx3 · 10-28-2014, 08:50 AM

Originally posted by ogl

Exposure value - Wikipedia, the free encyclopedia

Exposure times - 15 sec for f1.4 and EV-3. You need tripod to make photos in such condition.

EV
TYPE OF LIGHTING SITUATION
-6
Night, away from city lights, subject under starlight only.
-5
Night, away from city lights, subject under crescent moon.
-4
Night, away from city lights, subject under half moon. Meteors (during showers, with time exposure).
-3
Night, away from city lights, subject under full moon

That's cool, I'll remember that...

zoolander · 10-28-2014, 12:47 PM

Originally posted by ogl

Exposure value - Wikipedia, the free encyclopedia

Exposure times - 15 sec for f1.4 and EV-3. You need tripod to make photos in such condition.

EV
TYPE OF LIGHTING SITUATION
-6
Night, away from city lights, subject under starlight only.
-5
Night, away from city lights, subject under crescent moon.
-4
Night, away from city lights, subject under half moon. Meteors (during showers, with time exposure).
-3
Night, away from city lights, subject under full moon

I tried the AF in AF.C in complete darkness and it works, the picture taken was at ISO 51200 so its murky. But yeah, it does work.

It didn't work in AF.S mode, where I selected the single central point. I remember reading from reviewers through their personal experiences, that the center point and the one above andfbelow it were the best for low light auto focusing. So I'll test it out again tonight. I'm just a little surprised that it didn't work in AF.S mode.

So it works like a charm with the 50's and my 16-50 2.8 in AF.C mode - absolutely brilliant !

stevebrot · 10-28-2014, 01:38 PM

Originally posted by zoolander

that the center point and the one above andfbelow it were the best for low light auto focusing.

The three sensors in the center column are optimized for f/2.8 maximum aperture and wider. It is a matter of AF sensitivity* and is not related to light levels. As for AF-C vs. AF-S, that is not the way my K-3 works. I can get shutter release, but AF will not lock focus if there is not enough light regardless of mode.

Steve

* Most of the sensors are tuned for f/5.6 maximum aperture. What this means is that the PDAF system has the same ability to detect an out-of-focus state at f/5.6 as at f/1.4. With the center column this changes to f/2.8 meaning that those sensors are much more appropriate for use with fast lenses. I some ways the f/5.6 sensors may be more likely to (inappropriately) lock focus than the center column f/2.8 sensors.

10-28-2014, 02:32 AM	#1
zoolander Veteran Member Join Date: Dec 2012 Location: Gold Coast Photos: Albums Posts: 351	K-3 doesn't focus in low light conditions Hello all ! I just bought a new Pentax K-3 - woohoo ! But I tested out the low light focus ability in a dimly lit room, and it could not achieve focus on a gray bedspread and posts. I was using a Sigma 50mm 1.4, and also a Pentax FA 50mm 1.4, and both hunted. Only once did the Sigma get a lock. All at f/1.4. I had it on the center focus point, then tried it on using all the focus points. Does that sound right ? Its supposed to achieve focus in complete darkness, and this was a very dimly light room with the adjacent rooms light on. I was expecting it to achieve focus in complete darkness. (Also my flu card doesn't work and the K-3 doesn't see the card in slot 2. But I'll make another thread for this) Is this camera DOA ? Or am I doing something wrong(By the way, its an upgrade from my K-5, and its faster, sharper, stabler, quicker OS and snappier so I'm real happy ! )

10-28-2014, 07:34 AM	#7
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by zoolander I thought -3EV was complete darkness. Thats what people have been banging on about. No, -3 EV is not complete darkness, but it is dim enough that you probably would not be able to make your way without stumbling over something. Originally posted by zoolander In total darkness its not metering the picture but it is achieving focus in AF.C. It may have taken the photo in AF-C, but neither that nor the focus point lights in the viewfinder are evidence of acquired focus. AF-C with default settings will allow shutter release before focus is acquired The red focus point indicators merely show which point the camera is using Focus acquisition is signaled by the green hexagon at the bottom of the viewfinder display along with a beep Steve

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10-28-2014, 02:39 AM	#2
Steve.Ledger Veteran Member Join Date: Oct 2009 Location: Far North Qld Posts: 3,301	Originally posted by zoolander Its supposed to achieve focus in complete darkness Seriously?

10-28-2014, 02:41 AM	#3
RollsUp Veteran Member Join Date: Apr 2008 Location: AK USA Photos: Gallery Posts: 1,766	Have you updated the firmware for both the K-3 and the Flucard?

10-28-2014, 02:42 AM	#4
asp1880 Veteran Member Join Date: Jul 2010 Location: Lyngby, Copenhagen Photos: Albums Posts: 742	Two things: 1. The camera needs some contrast (lines, structure, pattern) to be able to focus. You can't expect it to focus on a featureless surface such as the clear blue sky, light or no light. Gray bedspread - that sounds a bit low contrast to me. 2. It's not supposed to achieve focus in complete darkness. It's spec'ed to work down to light level EV -3, which is equivalent to 1/2 second at f/1.4 and ISO 3200. Try some manual settings to work out which exposure renders the grey bedspread as midtone, and that's your light level. 3. These experiments are only interesting with the focus assist lamp disabled. Regards, --Anders.

10-28-2014, 02:52 AM	#5
rawr Veteran Member Join Date: Jun 2009 Posts: 11,913	The K-3 can certainly do it's job in very low-light. To test low-light AF, find a contrasty focus target, confirm focus in bright light, then dim the lights progressively until the AF stops working. You may find this useful BTW, from the Nikon D4 manual:

10-28-2014, 03:12 AM	#6
zoolander Veteran Member Join Date: Dec 2012 Location: Gold Coast Photos: Albums Posts: 351 Original Poster	Originally posted by Steve.Ledger Seriously? I thought -3EV was complete darkness. Thats what people have been banging on about. ---------- Post added 10-28-14 at 08:14 PM ---------- Originally posted by RollsUp Have you updated the firmware for both the K-3 and the Flucard? The K-3 is the Prestige edition and comes with the latest firmware - I checked it already. Adam cleared up the flucard for me on the other thread. The camera was bundled with an 8gb card which is not the original Pentax 16gb flucard, so I can only share photos and not have the tethering, which is a real bummer. ---------- Post added 10-28-14 at 08:18 PM ---------- Originally posted by asp1880 Two things: 1. The camera needs some contrast (lines, structure, pattern) to be able to focus. You can't expect it to focus on a featureless surface such as the clear blue sky, light or no light. Gray bedspread - that sounds a bit low contrast to me. 2. It's not supposed to achieve focus in complete darkness. It's spec'ed to work down to light level EV -3, which is equivalent to 1/2 second at f/1.4 and ISO 3200. Try some manual settings to work out which exposure renders the grey bedspread as midtone, and that's your light level. 3. These experiments are only interesting with the focus assist lamp disabled. Regards, --Anders. Thats exactly what I thought ! I was in AF.S, so I tried AF.C, and bingo ! AF points are lighting up and its hitting focus on the bedspread, and anything I like and even darker spots ! In total darkness its not metering the picture but it is achieving focus in AF.C. Thanks ---------- Post added 10-28-14 at 08:20 PM ---------- Originally posted by rawr The K-3 can certainly do it's job in very low-light. To test low-light AF, find a contrasty focus target, confirm focus in bright light, then dim the lights progressively until the AF stops working. You may find this useful BTW, from the Nikon D4 manual: Thanks, I'll keep that all in mind. Gotta love this forum !

10-28-2014, 08:46 AM	#8
ogl Banned Join Date: Dec 2007 Location: Sankt Peterburg Photos: Gallery \| Albums Posts: 8,382	Originally posted by zoolander I thought -3EV was complete darkness. Gotta love this forum ! Exposure value - Wikipedia, the free encyclopedia Exposure times - 15 sec for f1.4 and EV-3. You need tripod to make photos in such condition. EV TYPE OF LIGHTING SITUATION -6 Night, away from city lights, subject under starlight only. -5 Night, away from city lights, subject under crescent moon. -4 Night, away from city lights, subject under half moon. Meteors (during showers, with time exposure). -3 Night, away from city lights, subject under full moon

10-28-2014, 08:50 AM	#9
aleonx3 Veteran Member Join Date: Jul 2007 Location: Brampton, Ontario Photos: Gallery \| Albums Posts: 3,996	Originally posted by ogl Exposure value - Wikipedia, the free encyclopedia Exposure times - 15 sec for f1.4 and EV-3. You need tripod to make photos in such condition. EV TYPE OF LIGHTING SITUATION -6 Night, away from city lights, subject under starlight only. -5 Night, away from city lights, subject under crescent moon. -4 Night, away from city lights, subject under half moon. Meteors (during showers, with time exposure). -3 Night, away from city lights, subject under full moon That's cool, I'll remember that...

10-28-2014, 12:47 PM	#10
zoolander Veteran Member Join Date: Dec 2012 Location: Gold Coast Photos: Albums Posts: 351 Original Poster	Originally posted by ogl Exposure value - Wikipedia, the free encyclopedia Exposure times - 15 sec for f1.4 and EV-3. You need tripod to make photos in such condition. EV TYPE OF LIGHTING SITUATION -6 Night, away from city lights, subject under starlight only. -5 Night, away from city lights, subject under crescent moon. -4 Night, away from city lights, subject under half moon. Meteors (during showers, with time exposure). -3 Night, away from city lights, subject under full moon I tried the AF in AF.C in complete darkness and it works, the picture taken was at ISO 51200 so its murky. But yeah, it does work. It didn't work in AF.S mode, where I selected the single central point. I remember reading from reviewers through their personal experiences, that the center point and the one above andfbelow it were the best for low light auto focusing. So I'll test it out again tonight. I'm just a little surprised that it didn't work in AF.S mode. So it works like a charm with the 50's and my 16-50 2.8 in AF.C mode - absolutely brilliant !

10-28-2014, 01:38 PM	#11
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by zoolander that the center point and the one above andfbelow it were the best for low light auto focusing. The three sensors in the center column are optimized for f/2.8 maximum aperture and wider. It is a matter of AF sensitivity* and is not related to light levels. As for AF-C vs. AF-S, that is not the way my K-3 works. I can get shutter release, but AF will not lock focus if there is not enough light regardless of mode. Steve * Most of the sensors are tuned for f/5.6 maximum aperture. What this means is that the PDAF system has the same ability to detect an out-of-focus state at f/5.6 as at f/1.4. With the center column this changes to f/2.8 meaning that those sensors are much more appropriate for use with fast lenses. I some ways the f/5.6 sensors may be more likely to (inappropriately) lock focus than the center column f/2.8 sensors.