[Rupert]

For f=2.8 EV 4 would be:

0.5s @ISO 100,
1/4s @ISO 200,
1/8s @ISO 400,
1/15s @ISO 800,
1/30s @ISO 1600,
1/60s @ISO 3200,
1/125s @ISO 6400

(EV 0 by definition is 1s f=1 @ISO 100)

So would 1/30 @ISO 1600 F4 be a shot without worry? I shoot in this range fairly often...usually more at 6.7 with the Bigma? In fact, I seldom use 2.8 on anything, it requires very good glass and I only have a few lenses that give decent results at 2.8. If I am at f4 or above, am I safe from the FF issue?
Regards!

[Smeggypants]

So would 1/30 @ISO 1600 F4 be a shot without worry? I shoot in this range fairly often...usually more at 6.7 with the Bigma? In fact, I seldom use 2.8 on anything, it requires very good glass and I only have a few lenses that give decent results at 2.8. If I am at f4 or above, am I safe from the FF issue?
Regards!

not according to my tests you are not. Assuming your K-5 has the problem of course.

[Wheatfield]

So would 1/30 @ISO 1600 F4 be a shot without worry? I shoot in this range fairly often...usually more at 6.7 with the Bigma? In fact, I seldom use 2.8 on anything, it requires very good glass and I only have a few lenses that give decent results at 2.8. If I am at f4 or above, am I safe from the FF issue?
Regards!

That's right on the edge at EV5. I'd be watching my AF very closely.
Anything brighter than that should be OK, since the problem seems to show itself around EV4 and lower.

[peterh337]

I am still having a lot of trouble reproducing this issue, at the max aperture I have which is F4. Right now I am doing it at very low light (too dim to read by) using the spot focus mode. The AF assist light comes on but I put a finger over the LED and de-focus the lens before taking the shot. Admittedly it does take longer to focus...

Just taken some at 1/30 ISO5000 F4. They are OK.

1/30 ISO10000 F4, the camera won't AF.

Using the TAV mode.

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Last edited by peterh337; 01-16-2011 at 09:32 PM.

[Gimbal]

I am still having a lot of trouble reproducing this issue, at the max aperture I have which is F4. Right now I am doing it at very low light (too dim to read by) using the spot focus mode. The AF assist light comes on but I put a finger over the LED and de-focus the lens before taking the shot. Admittedly it does take longer to focus...

Just taken some at 1/30 ISO5000 F4. They are OK.

1/30 ISO10000 F4, the camera won't AF.

Using the TAV mode.

At what focal length? The kit zoom seems OK at 55mm but way out at 18mm

[Tommot1965]

I am still having a lot of trouble reproducing this issue, at the max aperture I have which is F4. Right now I am doing it at very low light (too dim to read by) using the spot focus mode. The AF assist light comes on but I put a finger over the LED and de-focus the lens before taking the shot. Admittedly it does take longer to focus...

Just taken some at 1/30 ISO5000 F4. They are OK.

1/30 ISO10000 F4, the camera won't AF.

Using the TAV mode.

what is the distance to the focal plane from the subject in your test shots ?

[cpk]

I photograph flamenco dancers. I used to shoot on Tmax 3200 with a Leica at 1/60 sec and f2, pushed if necessary. . . . The Leica was so good in this respect.

I should add that the Leicas I used (two at a time with different lenses) were the M series, rangefinders, which is why they were so good at focusing in the dim lighting conditions of nightclubs.

[peterh337]

I did the tests with a 16-45 set to 45.

I have now done more at 16.

I may be seeing a problem, just about. What happens, around the 1/30 F4 ISO8000 region, is that the AF assist light does not (yet) come on but the camera sometimes does not attempt to focus. Maybe it thinks it is focused already?

A relevant point may be that you can hear the 16-45 being focused, whereas a lot of you people are using the silent-focusing lenses and with those there is no way (?) to tell if the camera thinks it has done it.

The focus I am getting at the above setting (distance about 2-3ft) is not great but I cannot improve it manually under those conditions because I can't see anything much in the viewfinder. The light is just too low.

Incidentally, I am using the spot focus mode. Can one config the K5 to display a spot where it is focusing? I assume it is right in the centre of the screen.

[jolepp]

So would 1/30 @ISO 1600 F4 be a shot without worry? I shoot in this range fairly often...usually more at 6.7 with the Bigma? In fact, I seldom use 2.8 on anything, it requires very good glass and I only have a few lenses that give decent results at 2.8. If I am at f4 or above, am I safe from the FF issue?
Regards!

It is hard to say for sure. My understanding based on reading this forum would be that the problematic conditions are below 4 EV (possibly in combination with artifical/tungsten light), but then we don't know what is actually going on (e.g. this might be an overcompensation in tungsten light, might be something else). Also, some K-5 owners apparently being just fine might mean that we don't even have the relevant circumstances nailed down.

[Rupert]

Still confused........
"Also, some K-5 owners apparently being just fine might mean that we don't even have the relevant circumstances nailed down."

Initially I assumed these were wrong or just covering the problem because it was not much of a factor for them, but I know some of these people and they are neither incompetent or liars. So it does point to a defect either in hardware or software, or possibly both? It appears that only Pentax is going to be able to identify and repair the problem, and I am assuming that they will....that they will have to. They can't afford for the camera returns to keep piling up and continue to ship more future returns.
Just what the problem is should be very interesting, as there have been so many speculations already. A rapid solution would be most welcome, I want to place my order, and so do many others.
Regards & Thanks to those that answered my questions.

[Smeggypants]

It is hard to say for sure. My understanding based on reading this forum would be that the problematic conditions are below 4 EV (possibly in combination with artifical/tungsten light), but then we don't know what is actually going on (e.g. this might be an overcompensation in tungsten light, might be something else). Also, some K-5 owners apparently being just fine might mean that we don't even have the relevant circumstances nailed down.

Or some copies of the camera may perform better than other due to tolerances in manufacturing.

[elho_cid]

Still confused........
"Also, some K-5 owners apparently being just fine might mean that we don't even have the relevant circumstances nailed down."

My first K-5 focused perfectly. I never had the FF problem in dim lightning. It only appeared after the first K-5 was replaced by another one due to stains. Then I found this thread...
So I believe the problem is not appearing in all the K-5 and it cannot be solved by FW. I sent my K-5 for repair, and I made sure I explained it well to the technician.

Explaining it on the internet makes no sense...

[Pentaxeros]

Hola, insisto nuevamente, como ya dije en el otro post que trataba este problema.

TODAS las K-5 tienen este problema.

He probado una a una, mas de 100 unidades de K-5, ya que tengo una tienda especializada en Pentax (La Tienda Pentaxeros.com), incluso las ultimas cámaras de la serie 398xxxx, y TODAS, tienen este problema.

Pentax me ha dicho personalmente que es un problema de firmware.

Saludos cordiales...

[Horst-Helmut]

So, I was at the studio today and most of the ~100 shots I tried to take were so horribly FF I can't use them, again! If I focused on the shoulder that was behind the focus was almost correct, still leaving the edge of shoulder out of focus. Most of my time I tried to get the focus right and just had to call the whole thing off because these focusing issues just killed the mood completely.

75mm @ f9 from 3-3.5m = 0.57-0.77m total DOF and the poses we tried to shoot were not that deep.

I'm keeping the K-5 for outdoor stuff but getting another system for gigs and studio stuff.

[Smeggypants]

Hola, insisto nuevamente, como ya dije en el otro post que trataba este problema.

TODAS las K-5 tienen este problema.

He probado una a una, mas de 100 unidades de K-5, ya que tengo una tienda especializada en Pentax (La Tienda Pentaxeros.com), incluso las ultimas cámaras de la serie 398xxxx, y TODAS, tienen este problema.

Pentax me ha dicho personalmente que es un problema de firmware.

Saludos cordiales...

That's good to know Pentaxeros. Has Pentax told you when a solution is expected?