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03-13-2011, 08:24 AM   #241
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QuoteOriginally posted by Snydly Quote
Thanks, but I've seen some of the calculators. However, I think you answered the question I had... EV is determined 'after the shot', correct?

I've seen so many post here that they took a photo with "2 EV" for example, and have been assuming that they set the lighting at that value prior to shooting, when it appears that EV is taken from analyzing the parameters of photo data, or at least calculated by looking at the basic settings the camera decides to set with it's built in light meter. IOW, I could dial up or down my lighting and look at the parameters the camera calculates for correct exposure (ISO, shutter, aperture & ev), plug them into one of the programs some of you suggested here and I would have an EV number, is that right?

Again, sorry for off topic, I see you are all dealing with a very important and possibly frustrating issue. I hope this gets sorted out soon for all of you. I really want a k5 but have to decide if this issue isn't fixed, is it going to affect my type or style of shooting to the extent that using the camera would result in a negative experience for me.

Bill

Bill
jolepp, in the following link, I believe said it clearly. "Crucially this means that AF should now work with something like f=2.8 t=1/30s ISO=3200 (EV 3) even if there happens to be a tungsten bulb around"

https://www.pentaxforums.com/forums/pentax-k-5-forum/129738-k-5-user-auto-foc...ml#post1424041

Probably can work better than that in many cases, but do you shoot in situations darker than that? If not, you are O.K. Is that compatible with your style of shooting?

And you can measure EV before the shot with a light meter. So you can set the light level before the shot. You don't have to, but you can.

03-13-2011, 08:51 AM   #242
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QuoteOriginally posted by jrforman Quote
And you can measure EV before the shot with a light meter. So you can set the light level before the shot. You don't have to, but you can.
I'm off to shoot a wedding today with my K-5 (K100DS and K-x as backups). At the rehearsal yesterday the church metered out at 6ev and that was confirmed by the camera metering. Yesterday was a very bright day and a fair percentage of the light is coming from windows.

Today is overcast and gloomy. I guessing that the church will meter out at 4-5 EV, hopefully not less. Well see how the K-5 behaves. I know that the K100DS does not do well in that light with moving targets (people walking sown the aisle or dancing). I missed far too many shots with it. My thinking is that I will not completely miss any shots with the K-5, only question is whether it nails the focus. OTOH, a slightly missed focus is better than no shot at all.
03-13-2011, 09:14 AM - 1 Like   #243
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QuoteOriginally posted by Snydly Quote
Sorry to go off topic slightly here, but I've asked this question before and although many people tried to explain, I still didn't get it.

How do you determine and quantify EV? Do you have a light meter with an EV readout? I see people give an EV number and I would like to understand EV and how it's calculated or measured.

Thanks,

Bill
QuoteOriginally posted by Snydly Quote
How do you determine and quantify EV?

I have a small Excel spreadsheet that takes any values. Can't remember where I got it from, but it seems to work when compared to the reference tables. I don't know how to upload it here, but this is how to set it up:

If cell C2= Aperture, C3=Shutter speed (for 1/200, enter value as 200), C4=ISO, then EV calculation formula for cell C5 is: =((2*LOG10(C2)-LOG10(1/C3))-LOG10(C4/100))/LOG10(2)
03-13-2011, 03:09 PM   #244
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QuoteOriginally posted by bjdavey Quote
If cell C2= Aperture, C3=Shutter speed (for 1/200, enter value as 200), C4=ISO, then EV calculation formula for cell C5 is: =((2*LOG10(C2)-LOG10(1/C3))-LOG10(C4/100))/LOG10(2)
That works.

03-13-2011, 05:03 PM - 1 Like   #245
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For what it's worth, I created a Google Docs spreadsheet to calculate EV, luminance and illuminance - it's for public view, but to use it you can copy it to your own Google Docs space:
https://spreadsheets.google.com/ccc?key=0Ahto5-ljsK44dDRpeTA3SkZoNUlvLWVvYy1HWTktTUE&hl=en

And if anyone is interested, a DOF calculator:
https://spreadsheets.google.com/ccc?key=0Ahto5-ljsK44dDFYazFpVmhFSHg4RUYwMVhQVFNRV3c&hl=en
03-13-2011, 10:18 PM   #246
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QuoteOriginally posted by jrforman Quote
And you can measure EV before the shot with a light meter. So you can set the light level before the shot. You don't have to, but you can.
I guess I've never seen photographers describe their lighting condition with an EV like I've seen lately. Not saying they don't, I've just not been around any. The magazines and articles don't usually describe lighting with EV either, so I thought I was missing something.

It makes sense.

Thanks,

Bill
03-13-2011, 11:46 PM   #247
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QuoteOriginally posted by mrmentera Quote
How can everyone else on the forum get so consistent and reprodusable data? Is my K-5 (with 1.3) totally ****ed up? Are my lenses ****ed up? Or is it me??? Or is there a lot of testing on the forum that actually isn┤t reliable in all aspects and may cause some confuse? It would be nice to have some feedback on the aspects of the lenses mechanical construction that affect how AF behaves. Thanks.
I used the same test chart. With the previous firmware (1.02) I found it nearly impossible to get consistent results with the default test chart, because the grey text around the black focus target was too dark. The author of that chart does various versions for this exact reason. I think i ended up printing out the lightest chart (5% grey, i think). I then got much more consistent results IN A SINGLE LIGHT SOURCE. But then when I moved to a different light source (daylight shadow to fluorescent lighting), the calibration was out again. I re-adjusted again after that and managed to get fairly consistent results.

After having updated to 1.03 I haven't yet recalibrated my lenses. I reset all my calibration back to 0 again. I'm hoping when I try again I won't have the inconsistencies between the different light sources that I had before. We shall see.
03-14-2011, 01:35 AM   #248
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I just gotta say -- I just got back my replaced K-5 with firmware 1.03 installed. It's basically DEAD ON with all my lenses in any light. I'm so happy with the way this has been resolved. It's working out perfectly for me -- I don't even have to fiddle with micro-adjustment. Even my somewhat troublesome FA 50/1.7, which focused wrong on my K100D, K10D and my first K-5, is right on the money. I'm really satisfied.

03-14-2011, 04:11 AM   #249
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I have performed a test and unfortunately the problem is still there with 1.03. Tested with 3 different lensens. Might be just my K5 though...waiting for some other people to confirm with a similar test that their K5 is focussing fine, before I send mine back.

See the results here: focustest - a set on Flickr
03-14-2011, 04:21 AM   #250
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Firmware 1.03 Did Not Fix The Problem

I did my simple 5 minute test to see if the problem was completely resolved.
Unfortunately, as also Smeggypants has confirmed, the FF issue has not been completely fixed.

In the firmware description, it says: AF improved in low light conditions. This may be the case, since the -10 AF fine adjustment seems to compensate slightly better for the FF, but I am not sure. I also have the feeling the the FF threshold at which the FF issue occurs has been lowered.

All I want is to take reliable dance photos and that will be the test for me whether the camera operates the way I want.
03-14-2011, 05:50 AM   #251
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I've got a perfectly functioning K5 that I am thrilled with. I feel left out.
03-14-2011, 06:08 AM   #252
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QuoteOriginally posted by youyou Quote
I have performed a test and unfortunately the problem is still there with 1.03. Tested with 3 different lensens. Might be just my K5 though...waiting for some other people to confirm with a similar test that their K5 is focussing fine, before I send mine back.

See the results here: focustest - a set on Flickr
QuoteOriginally posted by Eric Seavey Quote
I did my simple 5 minute test to see if the problem was completely resolved.
Unfortunately, as also Smeggypants has confirmed, the FF issue has not been completely fixed.

In the firmware description, it says: AF improved in low light conditions. This may be the case, since the -10 AF fine adjustment seems to compensate slightly better for the FF, but I am not sure. I also have the feeling the the FF threshold at which the FF issue occurs has been lowered.

All I want is to take reliable dance photos and that will be the test for me whether the camera operates the way I want.
Did you guys take field curvature of your lenses into account before you made this pronouncement?
03-14-2011, 06:54 AM   #253
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QuoteOriginally posted by Wheatfield Quote
Did you guys take field curvature of your lenses into account before you made this pronouncement?
The thing is, that if LiveView performs more accurate focus than normal AF, with everything else being equal, then something is obviously not quite optimal.
03-14-2011, 08:31 AM   #254
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QuoteOriginally posted by Wheatfield Quote
Did you guys take field curvature of your lenses into account before you made this pronouncement?
By how much do you think field curvature affects AF? We're talking about several cm of FF at a distance of less than a meter, not just "missed by a hair" focus.
03-14-2011, 11:44 AM   #255
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QuoteOriginally posted by Wheatfield Quote
Did you guys take field curvature of your lenses into account before you made this pronouncement?
No.

Because it's unnecessary when we are dealing with inaccuracies far larger than any field curvature. Same reason I didn't bother exactly lining up the focus chart.
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