What to do with my low light FF problem

Smeggypants · 06-26-2011, 09:33 PM

Originally posted by _phil_

I dimmed the lights until the focus assist light came on and then covered it with my hand, forced a refocus and took some shots. I assume this was dark enough to show any FF problem. There was none. I had previously calibrated the lens focus in sunlight. There was no discernable change with incandescant.

Build: 02/17/2011
Version: 1.03

What lens and what aperture did you test this at?

**Eric Seavey** · 06-27-2011, 06:14 AM

I didn't have time to test last night, but hopefully tonight I can show some results here.

In every other way I do really like the K-5. I just cannot imagine that the new camera I bought just coincidentally also has the FF problem.

I am shooting a dance coming Friday, and will try out my "repaired" K-5 to see if there has been any improvement.

Eric

_phil_ · 06-27-2011, 07:24 AM

Originally posted by smeggypants

what lens and what aperture did you test this at?

DA50-135 @135 f2.8
EDIT:
Ok, just had another go (in dull incandescant) with different lens (DA17-70)... F4, 1/4, 3200 and I can barely see what I'm taking (manual focus impossible). Perfect focus and if I'm not mistaken, about 1EV.

I'm not gloating... just the result for one camera.

magnosantos · 06-27-2011, 07:37 AM

It seems i'm lucky. Yes i had FF issues but they seem consistent with all light conditions.

garyk · 06-27-2011, 02:29 PM

I have the same results that Eric Seavey has. Exactly!! Having only Pentax and never another brand. I am going to buy a canon 328 with the 7D I think, and check it against the Pentax K-5 and Sigma 328 lens. I am kinda curious about the differences if any. When i get the canon equipment and test I will post my thoughts.

mikknu · 06-28-2011, 03:40 AM

Originally posted by Eric Seavey

The bad news is that they both are exhibiting the front focus problem. It doesn’t even have to seem to be that dim for this problem to occur. Also, it occurs when there is still too much light to trigger the focus assist light. It seems that the AF (without AF assist light) starts getting unreliable under 2 EV.

I seem to have the same problem with FF on my K-5, posted some threads about it as well, though at the time I thought it was a lens quality thing, but that seems less likely the more I think about it. Tried 3 different lenses and they all seemed to give me FF.

So now my K-5 is in for repairs/calibrating, depending on what they find wrong with it, if anything at all... Therefor I am a bit interested in how you handle this.

**Eric Seavey** · 06-29-2011, 08:01 AM

Update:
I have done some hypothesis testing last night and found a difference between dimming a light with a dimmer (resulting in a shift towards red) and having a little light coming from another room.
My preliminary tests are showing severe FF with the dimmed light, and acceptable focus from a bright light leaking in from another room.
I also looked into adding an IR cut filter vs no IR cut filter when focusing in dimmed lit conditions. Preliminary results are showing a difference in focus behavior. Where the camera was able to focus without the IR filter, there was no ability to focus with the IR-cut filter on the lens.
My question is now related to the camera using IR to help the AF, and why it affects the AF on the K-5 and not the K10D? I do know that AF can be used with a number of lenses for IR photography, despite the focus shift in IR.

More to come....

Eric

garyk · 06-29-2011, 10:01 AM

I just purchased a new Canon 7D which is suppose to be the K-5 equivalent. Also I purchased a Canon 300mm f2.8 lens. When my K-5 gets back from Japan service. I will put the Sigma 300mm 328 on it and do a comparison.
That said I will defiantly keep the Pentax even if the Canon blows it away ( or not ). But as a wildlife photographer I want to know if the Canon is a better system. I am very unhappy with the K-5 so far. It just cannot handle my 328 lens and AF. I am at a dead end with Pentax I do not know what else to do but to try another system to see if it is better. If not I will post the findings.

rawr · 06-29-2011, 03:47 PM

Originally posted by garyk

try another system to see if it is better.

An expensive experiment!

The two systems are hard to compare on the basis of their simple AF specs - eg:

7D
• 19 cross-type AF points (f/2.8 at centre)
• Center point additionally sensitive with lenses of F2.8 or faster
• AF working range: -0.5 - 18 EV (at 23°C, ISO 100)

K-5
• 11-point TTL Phase Difference detection sensor (SAFOX IX+)*
• Center 9-points are sensitive to both horiz and vert. detail
• AF working range: -1 to 18 EV (at ISO 100, F1.4 lens)

On the basis of these specs a K-5's AF should work in slightly lower light than the 7D's. The K-5's EV sensitivity even looks a lot like the current camera AF king, the Nikon D3s:

• 51 focus points (15 cross-type sensors)
• Multi-CAM 3500FX
• AF working range: -1 to +19 EV (ISO 100, normal temperature)

Even the old faithful K-x's AF (on paper) looks more sensitive than the 7D in low-light:
• 11-point wide autofocus system (SAFOX VIII)*
• TTL Phase matching
• AF working range: -1 to 18 EV (at ISO 100, F1.4 lens)

Be keen to see how you go.

garyk · 06-29-2011, 06:09 PM

If the Canon does not meet my expectations I will sell it. And move on and quit griping..

I think out very little for peace of mind. Who knows maybe the K-5 will kick ass... Then I can put it to the canon folks... LOL
Either way I have to know.

rawr · 06-29-2011, 07:28 PM

Originally posted by garyk

Either way I have to know

Yeah, ultimately the only real way to test something out is to use it for a while and put it to work. Hands on sure beats reading brochures or looking at websites. You may find the AF is ordinary on the 7D, but it might have other virtues that make it better than the K-5 for your kind of work that you can't anticipate until you've used it for a while. Horses for courses.

06-27-2011, 07:24 AM	#18
_phil_ Junior Member Join Date: Aug 2009 Location: Melbourne Posts: 25	Originally posted by smeggypants what lens and what aperture did you test this at? DA50-135 @135 f2.8 EDIT: Ok, just had another go (in dull incandescant) with different lens (DA17-70)... F4, 1/4, 3200 and I can barely see what I'm taking (manual focus impossible). Perfect focus and if I'm not mistaken, about 1EV. I'm not gloating... just the result for one camera. Last edited by _phil_; 06-27-2011 at 07:55 AM.

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06-26-2011, 09:33 PM	#16
Smeggypants Veteran Member Join Date: Sep 2010 Posts: 1,536	Originally posted by _phil_ I dimmed the lights until the focus assist light came on and then covered it with my hand, forced a refocus and took some shots. I assume this was dark enough to show any FF problem. There was none. I had previously calibrated the lens focus in sunlight. There was no discernable change with incandescant. Build: 02/17/2011 Version: 1.03 What lens and what aperture did you test this at?

06-27-2011, 06:14 AM	#17
Eric Seavey Site Supporter Join Date: Feb 2008 Location: Irvine, CA Photos: Gallery \| Albums Posts: 307 Original Poster	I didn't have time to test last night, but hopefully tonight I can show some results here. In every other way I do really like the K-5. I just cannot imagine that the new camera I bought just coincidentally also has the FF problem. I am shooting a dance coming Friday, and will try out my "repaired" K-5 to see if there has been any improvement. Eric

06-27-2011, 07:37 AM	#19
magnosantos Junior Member Join Date: May 2011 Location: Lisboa Photos: Gallery Posts: 46	It seems i'm lucky. Yes i had FF issues but they seem consistent with all light conditions.

06-27-2011, 02:29 PM	#20
garyk Inactive Account Join Date: Feb 2010 Photos: Gallery Posts: 488	I have the same results that Eric Seavey has. Exactly!! Having only Pentax and never another brand. I am going to buy a canon 328 with the 7D I think, and check it against the Pentax K-5 and Sigma 328 lens. I am kinda curious about the differences if any. When i get the canon equipment and test I will post my thoughts.

06-28-2011, 03:40 AM	#21
mikknu Forum Member Join Date: Dec 2010 Location: Silkeborg, Denmark Posts: 82	Originally posted by Eric Seavey The bad news is that they both are exhibiting the front focus problem. It doesn’t even have to seem to be that dim for this problem to occur. Also, it occurs when there is still too much light to trigger the focus assist light. It seems that the AF (without AF assist light) starts getting unreliable under 2 EV. I seem to have the same problem with FF on my K-5, posted some threads about it as well, though at the time I thought it was a lens quality thing, but that seems less likely the more I think about it. Tried 3 different lenses and they all seemed to give me FF. So now my K-5 is in for repairs/calibrating, depending on what they find wrong with it, if anything at all... Therefor I am a bit interested in how you handle this.

06-29-2011, 08:01 AM	#22
Eric Seavey Site Supporter Join Date: Feb 2008 Location: Irvine, CA Photos: Gallery \| Albums Posts: 307 Original Poster	Update: I have done some hypothesis testing last night and found a difference between dimming a light with a dimmer (resulting in a shift towards red) and having a little light coming from another room. My preliminary tests are showing severe FF with the dimmed light, and acceptable focus from a bright light leaking in from another room. I also looked into adding an IR cut filter vs no IR cut filter when focusing in dimmed lit conditions. Preliminary results are showing a difference in focus behavior. Where the camera was able to focus without the IR filter, there was no ability to focus with the IR-cut filter on the lens. My question is now related to the camera using IR to help the AF, and why it affects the AF on the K-5 and not the K10D? I do know that AF can be used with a number of lenses for IR photography, despite the focus shift in IR. More to come.... Eric

06-29-2011, 10:01 AM	#23
garyk Inactive Account Join Date: Feb 2010 Photos: Gallery Posts: 488	I just purchased a new Canon 7D which is suppose to be the K-5 equivalent. Also I purchased a Canon 300mm f2.8 lens. When my K-5 gets back from Japan service. I will put the Sigma 300mm 328 on it and do a comparison. That said I will defiantly keep the Pentax even if the Canon blows it away ( or not ). But as a wildlife photographer I want to know if the Canon is a better system. I am very unhappy with the K-5 so far. It just cannot handle my 328 lens and AF. I am at a dead end with Pentax I do not know what else to do but to try another system to see if it is better. If not I will post the findings.

06-29-2011, 03:47 PM	#24
rawr Veteran Member Join Date: Jun 2009 Posts: 11,913	Originally posted by garyk try another system to see if it is better. An expensive experiment! The two systems are hard to compare on the basis of their simple AF specs - eg: 7D • 19 cross-type AF points (f/2.8 at centre) • Center point additionally sensitive with lenses of F2.8 or faster • AF working range: -0.5 - 18 EV (at 23°C, ISO 100) K-5 • 11-point TTL Phase Difference detection sensor (SAFOX IX+)* • Center 9-points are sensitive to both horiz and vert. detail • AF working range: -1 to 18 EV (at ISO 100, F1.4 lens) On the basis of these specs a K-5's AF should work in slightly lower light than the 7D's. The K-5's EV sensitivity even looks a lot like the current camera AF king, the Nikon D3s: • 51 focus points (15 cross-type sensors) • Multi-CAM 3500FX • AF working range: -1 to +19 EV (ISO 100, normal temperature) Even the old faithful K-x's AF (on paper) looks more sensitive than the 7D in low-light: • 11-point wide autofocus system (SAFOX VIII)* • TTL Phase matching • AF working range: -1 to 18 EV (at ISO 100, F1.4 lens) Be keen to see how you go.

06-29-2011, 06:09 PM	#25
garyk Inactive Account Join Date: Feb 2010 Photos: Gallery Posts: 488	If the Canon does not meet my expectations I will sell it. And move on and quit griping.. I think out very little for peace of mind. Who knows maybe the K-5 will kick ass... Then I can put it to the canon folks... LOL Either way I have to know.

06-29-2011, 07:28 PM	#26
rawr Veteran Member Join Date: Jun 2009 Posts: 11,913	Originally posted by garyk Either way I have to know Yeah, ultimately the only real way to test something out is to use it for a while and put it to work. Hands on sure beats reading brochures or looking at websites. You may find the AF is ordinary on the 7D, but it might have other virtues that make it better than the K-5 for your kind of work that you can't anticipate until you've used it for a while. Horses for courses.