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12-18-2010, 12:20 PM   #16
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Planedriver/ The fast (enough) shutter speed is outside of the issue I want to bring up here. Fast enough shutter speed is a given thing as far as I estimate the skill level of our members. WIth flash the shutter speed is no issue anyway. (your pic is nicely made without flash and the 1/50 and a quitly sitting father did no harm to sharpness in the image)

12-18-2010, 12:43 PM   #17
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QuoteOriginally posted by bjan Quote
Planedriver/ The fast (enough) shutter speed is outside of the issue I want to bring up here.
I know I know..I'm only talking about my impressions (when taking candid portraits)..and I have to tell you I have a lot's of missed focused pictures at tungsten light with the 55-300 at any of it's fastest apertures and even with the FA50 it's very easy to miss..

..but as soon as my new K-5 arrives (stain issue) I'll try it on some static objects too.

Andras
12-18-2010, 12:57 PM   #18
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QuoteOriginally posted by Winder Quote
The K-7 is not particularly accurate in low light conditions, but I was hoping the K-5 would be much improved. I still use my 5D for tough light, and while it is slower than the K-7, the 5D is pretty consistent in low/difficult light. Hopefully Pentax can improve the AF accuracy. I really like the compact size of the K-7/K-5 and the quiet shutter compared to my 5D.
No question (in my mind) that the K-5 is better in low light (in terms of AF speed) compared to the K-7. I was just suggesting that if you look closely enough, you'll still see that under very low temperature light (Tungsten and specifically even lower temp light), the AF system will still slightly front focus compared to daylight condition. This is obviously most apparent on very fast lenses (f/1.2-f/1.4) and from my experience, certain lenses exhibit more potential FF under these conditions than others.

Last edited by dgaies; 12-18-2010 at 01:39 PM.
12-18-2010, 01:03 PM - 7 Likes   #19
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Hola, soy el administrador de Pentaxeros.com, el foro Pentax en Español, y de una tienda de fotografia especializada en Pentax.

Hace ya tiempo, realice un estudio que reporte a Pentax sobre los problemas de enfoque bajo luz de tungsteno.
Analice mas de 25 unidades de K-5, y todas responden igual.

Las condiciones son las siguientes, y el Front Focus que se produce es siempre igual bajo dichas condiciones.

Las condiciones lumínicas son:
1/10 ISO 3200 f:2.8 y luz de Tunsgeno
Bajo parámetros de exposición similar, con luz de tungsteno, se produce un front focus que se puede corregir desde la opción de micro ajustes, con un ajuste de -10

Sin embargo bajo la misma intensidad lumínica, pero con luz natural, el enfoque es perfecto.

El problema se acentua aun mas con lentes con enfoque mediante tornillo. Con lentes SDM no lo he detectado.

El estudio lo realice bajo condiciones controladas, probando, la K-7, la K-5 y la K-r

La K-7 enfocaba siempre bien, el enfoque era lento, pero preciso.
La K-5 y la K-r siempre bajo luz de tungsteno tenian un Front focus de -10

El error lo reporte a Pentax, junto a todos los números de serie analizados, y RAW de las tomas realizadas y Pentax me ha informado que trabajan en ello para solucionarlo mediante firmware.

Espero haber arrojado luz sobre el asunto, ademas tambien se que en breve tendra solución.

Saludos cordiales...


12-18-2010, 01:56 PM   #20
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Thanks Pentaxeros. It is a bloody shame that PENTAX gave all this hassle to us their faithfull clients !
I have already returned my copy of the K5 after having tried everyting possible to conquer the problem. I hope a lot of buyers will do so in order to PUSH Pentax to act very very swift now ! For the price of a K5 one may expect a accurate AF in all light conditions. (exept at too dim light to find a focus ofcourse)
In case you start to play with the microadjustments you might encounter other problems with different AF at different distances especially with zoom lenses. Things should be good from the beginning without giving us the consumers the responsibility to make the AF work properly.
12-18-2010, 03:11 PM   #21
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after having been reading a bit in older threads I have found the existance of the tungsten light AF with fast lensen for many years. (also in other brands) Why should we expect Pentax to solve the issue all of a sudden with a firmware update ? I think I might feel more comfortable with my CANON S95 indoors in respect of focus accuracy than with my expensive Dsrl right ? I think the industry will tell us to buy 2 camera`s . 1 set for daylight and 1 set for artificial light. Not a funny joke because this is the situation that we are all in at the moment if we would like to shoot troublefree in respect of AF. The whole hype around being able to shoot in dim conditions without using flash with the latest dslrs is down the drain if you cannot shoot wide open. It is better to shoot with max ISO 400 and 2.8 than with ISO 1600 and being forced to use minimal 5.6.

By the way, would fast contrast detection development solve the issue ? I am not techinical enought to judge this. Just with an eye to the upcoming FUJI X100 that has contrast decection and a F2.0 lens. Would be a "joke" in case this camera had the tungsten light issue to right ?
12-18-2010, 03:23 PM   #22
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QuoteQuote:
after having been reading a bit in older threads I have found the existance of the tungsten light AF with fast lensen for many years. (also in other brands) Why should we expect Pentax to solve the issue all of a sudden with a firmware update ?
That was my point in my earlier reply. This isn't a Pentax only issue, it's an AF issue that has been around for quite some time. I would say there has been improvement, but it's certainly not perfect.

QuoteQuote:
I think I might feel more comfortable with my CANON S95 indoors in respect of focus accuracy than with my expensive Dsrl right ?
Well, since the sensor size of the S95 is a fraction of the K-5, the DOF is going to quite a bit larger for a given aperture/FL combo. So regardless of how the AF systems compare in terms of accuracy (and the S95 might be more accurate, I'm not sure), the shots are going to appear to be in better focus with the S95 because the DOF is so much larger.

QuoteQuote:
I think the industry will tell us to buy 2 camera`s . 1 set for daylight and 1 set for artificial light. Not a funny joke because this is the situation that we are all in at the moment if we would like to shoot troublefree in respect of AF. The whole hype around being able to shoot in dim conditions without using flash with the latest dslrs is down the drain if you cannot shoot wide open. It is better to shoot with max ISO 400 and 2.8 than with ISO 1600 and being forced to use minimal 5.6.
No disrespect intended, but that sounds a bit dramatic. First of all, you are free to change your AF adjustment for daylight/artificial light if you wish, no need for a second body. Personally I don't think that's a very good solution as I would tend to forget what it's set for and get myself into trouble. People in the past have suggested you could tie two different sets of adjustments to the WB selection. Again, not perfect, but potentially a step in the right direction.

An, for the record, the notion that shooting wide open is not "down the drain" or that you have to shoot f/5.6 to get in focus shots is simply not true.
12-18-2010, 03:34 PM   #23
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QuoteOriginally posted by bjan Quote
Hey Ron Hendriks,
That portrait seems to be made with a wider than 50 mm to me . You will have a dof of several inchess and not facing the issue here even wide open. Sharp it is though.
DA 40mm/f2.8 Ltd at f2.8

12-18-2010, 03:35 PM   #24
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QuoteOriginally posted by dgaies Quote
Well, since the sensor size of the S95 is a fraction of the K-5, the DOF is going to quite a bit larger for a given aperture/FL combo. So regardless of how the AF systems compare in terms of accuracy (and the S95 might be more accurate, I'm not sure), the shots are going to appear to be in better focus with the S95 because the DOF is so much larger.
Ditto this. Most P&S focusing systems use contrast-detect AF since they essentially use liveview all the time and this is *not* very accurate...it's just that they have a large DOF, so you don't notice errors much...

Glad Pentaxeros did a scientific test and sent the results to Pentax...well done...
12-18-2010, 05:02 PM   #25
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QuoteOriginally posted by bjan Quote
I think it is hard to argue or discuss about the issue without physically being together and being able to show picturewise ad hoc the findings and meaning of our words. However I am jealeaous to those who don`t experience any serious AF issue whereas I am completed frustrated by wanting to like the K5 very much but had to return it because of the large aperture tungsten AF issue that I don`t want to work around.
Out of curiosity, what is your white balance set to when you are having focus accuracy problems under tungsten light?
12-18-2010, 05:03 PM   #26
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QuoteOriginally posted by bjan Quote
Take the 2.8 or faster aperture with your 35 or longer lens . AF on a short distance ( 50 cm till 1 metre) and you will get ZERO pictures in focus in artificial light conditions !
I noticed too, that there is a problem with AF in poor light conditions at short distances with non-wide mm - when AF assist light is necessary for camera to autofocus - the AF assist light covers small area and if the red point isn't in that green light, the camera doesn't focus at all.
12-18-2010, 05:19 PM   #27
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QuoteOriginally posted by dgaies Quote
No question (in my mind) that the K-5 is better in low light (in terms of AF speed) compared to the K-7. I was just suggesting that if you look closely enough, you'll still see that under very low temperature light (Tungsten and specifically even lower temp light), the AF system will still slightly front focus compared to daylight condition. This is obviously most apparent on very fast lenses (f/1.2-f/1.4) and from my experience, certain lenses exhibit more potential FF under these conditions than others.
^^^^^ Exactly.. I've noticed this on every camera I've had but it's better on the K5 than it was with the K10d (which would just give up after cycling the focus from end to end).

I haven't done a lot of experimenting with it but



http://farm6.static.flickr.com/5246/5264884379_96956f046a_o.jpg

The actual focal point is the hand car and specifically, Santa. It's sharp enough for web presentation but if you go into Pixel peep mode looking at the full size, you'll see it's FF. The photo was taken with the FA77 f1.8 Limited, AWB IIRC. The only actual lighting for focusing is the lights from the Christmas tree above (that cannot be seen in the photo of course). The shot was taken with a flash (built in) however. In contrast to that, under CFL lighting,

http://www.rolleiman.com/Photos/HelpandStuff/31mmReview/K5JS1756_mFA31f18_Review_Dec15_f18.jpg

FA31mm f1.8 @ f1.8, Metz 58AF-1. DOF is quite shallow of course but the focal point (center) is dead on. A nice fix feature to this would be the ability to assign a lens correction (focus adjust) to one of the user modes (maybe we can now, I've never tried it).

12-18-2010, 05:21 PM   #28
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Where are all the photos with the supposed problems?
With all due respect to bjan and Pentaxeros all talk and no photos means nothing.
I haven't encountered the kind of focus errors with my K-5 with my fast lenses and if there were, it could be for a number of reasons, user error being one of them.
12-18-2010, 05:43 PM   #29
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Interesting...and I have no idea as to the reality of this claim, one way or the other. I can see that here are many that value the AF over all else, but just for the record, there are many like me that most often prefer MF for the better control and accuracy. Reports I have heard personally from new K5 owners do not reflect a problem, in fact very much the opposite, but for me it is not nearly as important as the other great features that are not in question.
Regards
12-18-2010, 06:51 PM   #30
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QuoteOriginally posted by Wheatfield Quote
Out of curiosity, what is your white balance set to when you are having focus accuracy problems under tungsten light?
Interesting question, Wheatfield. What are you getting at?

I'm puzzling away (instead of doing something constructive) trying to see the connection between WB and AF.

Please understand I'm not debating - simply asking.

Thanks!
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