[coley fillet]

Hello all,

I recently purchased a K-x to replace my Olympus E-P1. Since using the K-x I have noticed that my images lack sharpness compared to the E-P1. My plan from the start was to sell the E-P1 on ebay after buying the K-x so yesterday I decided to take a few shots of the E-P1 ready for selling. Whilst taking the shots I decided to use live view and noticed an instant improvement in sharpness. I really can't tell if it is the lens or the camera thats at fault and wondered what you guys thought. Heres a link showing two shots of the same image, one with conventional auto focus (top) and the other with Live View auto focus (bottom). Both images where shot under studio lights, camera on tripod and focus on the same point. Any help would be much appreciated.

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Last edited by coley fillet; 03-03-2010 at 01:06 AM.

[WerTicus]

well the kx uses contrast focus for lv and phase for normal shooting, so it could be a problem with the phase calibration.

[Karellen]

well the kx uses contrast focus for lv and phase for normal shooting, so it could be a problem with the phase calibration.

Hmm... I tried and discovered the same! Not so pronounced (I shoot with FA31), but it exists. Well then, how do we calibrate our phases, eh? %) I cannot imagine using LV even only for sharp landscaping.

[firefly]

Hmm... I tried and discovered the same! Not so pronounced (I shoot with FA31), but it exists. Well then, how do we calibrate our phases, eh? %) I cannot imagine using LV even only for sharp landscaping.

You can put the camera into debug mode to adjust the calibration. My k-x needed -70 to be sharp using phase detect AF. Just google "k-x debug af adjustment" and I'm sure you'll find ample tutorials.

[coley fillet]

Thanks for your replies.

I didn't mention that the linked image was taken with a Tamron 17-50mm.
The kit lens looks to be blurred when using phase or contrast focus in good light. I think I will have to test the kit lens more under the studio lights.

You can put the camera into debug mode to adjust the calibration. My k-x needed -70 to be sharp using phase detect AF. Just google "k-x debug af adjustment" and I'm sure you'll find ample tutorials.

I have read about the debug adjustment but can't really see why I should have to do this
after spending almost £500 on a camera, would I need to do this with a Canon 500D or Nikon D5000 which are the other two DSLR's I also considered.

I really hope I can sort this out because the potential quality I am seeing when using the Live view (contrast) auto focus is exceptional and far better performance than my E-P1.

[firefly]

I have read about the debug adjustment but can't really see why I should have to do this after spending almost £500 on a camera, would I need to do this with a Canon 500D or Nikon D5000 which are the other two DSLR's I also considered.

I really hope I can sort this out because the potential quality I am seeing when using the Live view (contrast) auto focus is exceptional and far better performance than my E-P1.

There are two different optical paths when using phase detect. The autofocus feature allows for some offset which is accessible in the debug mode. The offset is there to correct for an unexpected difference between the length of those two optical paths.

I'm guessing other cameras that use phase detect suffer from small variations as well. If you've never noticed it before it could be because:

- that particular camera did not have a large variance
- the camera manufacturer had already carefully calibrated it, or
- the camera was manufactured with tighter tolerances.

Remember the k-x is marketed as an entry level camera. Although it has an excellent sensor and produces great image quality, I can see how this would be shipped out the door knowing that they have some larger variances than normal. I think the expectation for the k-x was to be used with slower kit lenses, which would mask the problem to a large degree.

[sterretje]

Search for focus or repair using your browser search in the web pages below; you might have to go one or two pages further.

Canon EOS 1000D / 500D - 300D Forum: Digital Photography Review
Nikon D90 - D40 / D5000 Forum: Digital Photography Review

Looks like the Canons have some problems as well. If I remember correctly, Canon seems to have (or had) a focusing issue with their latest 5D (a camera that costs far more than your one).

I could not find them easily for the Nikons (I found a D90 story); maybe search the internet if you really want to know.

I normally don't search for other peoples/brands problems but in this case I just wanted to point out that the other brands also have their problems.

The grass is always greener at the other side

[coley fillet]

Search for focus or repair using your browser search in the web pages below; you might have to go one or two pages further.

Canon EOS 1000D / 500D - 300D Forum: Digital Photography Review
Nikon D90 - D40 / D5000 Forum: Digital Photography Review

Looks like the Canons have some problems as well. If I remember correctly, Canon seems to have (or had) a focusing issue with their latest 5D (a camera that costs far more than your one).

I could not find them easily for the Nikons (I found a D90 story); maybe search the internet if you really want to know.

I normally don't search for other peoples/brands problems but in this case I just wanted to point out that the other brands also have their problems.

The grass is always greener at the other side

I made that statement due to the fact that there seems to be a lot of problems posted across the net regarding the K-x and sharpness. I previously owned Canon and Olympus cameras and must of been lucky not to have any problems. You must admit that this Pentax kit lens just doesn't hit the mark compared to the other brands unless I have a very bad copy. I have always wanted to try a Pentax camera and really want to love the K-x, I have chosen Pentax over the other brands after all. I just don't think the excuse's I keep hearing are really good enough, like "its an entry level camera" and "the QC is rushed because of its low price".

[firefly]

I just don't think the excuse's I keep hearing are really good enough, like "its an entry level camera" and "the QC is rushed because of its low price".

I'd like to point out that my above two points were not meant as an excuse, but rather a reflection of reality. I, too, agree that these problems are easily 'calibrated' out and should be done before sending these units out the door. Quite a shame they don't do this very well, actually.

If you want to give the k-x a chance, perform the calibration and give it a try. Although I sympathize with you, complaining about the issue will not resolve it. Good luck with it.

[coley fillet]

I'd like to point out that my above two points were not meant as an excuse, but rather a reflection of reality. I, too, agree that these problems are easily 'calibrated' out and should be done before sending these units out the door. Quite a shame they don't do this very well, actually.

If you want to give the k-x a chance, perform the calibration and give it a try. Although I sympathize with you, complaining about the issue will not resolve it. Good luck with it.

Wasn't specifically aimed at you Firefly, just what I've been hearing around the net.

I thought the debug focus calibration was for lenses that front or back focussed not for a problem with the cameras phase focussing.

If calibration worked with my Tamron 17-50mm, how will it affect other lenses that I might buy in the future?

[sterretje]

... You must admit that this Pentax kit lens just doesn't hit the mark compared to the other brands

Just over a year ago, it was the best of the bunch (reviews on the net). I'm reasonable happy with it (very happy with the DA55-300).

I don't own a Kx so can not comment on it and on the validity of the claims. I agree that a low price is no excuse for bad QC. However the sample size might be smaller and therefore more bad apples can reach the market.

If you're not happy with the camera and/or lens, I suggest that you take it back to the store and let them have a look at it and compare it with another one. It's still under warranty so fixing should not be an issue and swapping it might also be a possibility as well.

By the way, after buying a FA31, my K10D had to go in because of focusing issues. I suspected them, but the FA31 basically proved them because of the f/1.8 aperture resulting in a shallow DOF. Because of this, my next camera will be one where I can adjust the path (K20D/K7/,,,,,)

[firefly]

I thought the debug focus calibration was for lenses that front or back focussed not for a problem with the cameras phase focussing.

If calibration worked with my Tamron 17-50mm, how will it affect other lenses that I might buy in the future?

My apologies, I may have been a bit touchy.

Yes, the calibration would affect all other lenses as well. If the camera has a focus accuracy problem, the correction will fix all the lenses. However, if you have a defective lens causing the problem, and you calibrate to fix *that* lens, then all the other good lenses will all be thrown off.

In my case, the -70 adjustment corrected all my lenses. I never noticed it until I started shooting my fast manual 50 f1.4 wide open. After correcting for the manual 50 f1.4, I tested with my other lenses, and found them to be marginally sharper.

I would not have noticed the inaccuracy if it weren't for the 50.

[OutOfFocus]

I tried this test on my K-x using a tripod, the two second timer, ISO 200, and MF for four different lenses. Each lens was at its respective maximum aperture.

Initially I tried just one normal shot versus one LV shot for each lens. For three lenses the LV shot was clearly better focused but for the fourth they were about the same.

I went back and repeated the test on the lens which appeared to have the best focus in LV (and better focus than the normal shot). This time I took three different normal shots, each time defocusing then refocusing and making sure the green hexagon was lit. One shot was extremely close to the LV shot in focus quality, one was only marginally worse, and one was quite a way off. The variation in focus among the three shots was much greater than the difference between the best normal shot and the LV shot.

I suspect that for my K-x at least, the focus adjustment is pretty close to correct and that the focus indicator is lit for a wider focus range than I can get manually using LV.

(Focus estimates done both by eye and by a little python script I wrote to measure edge sharpness.)

[mattdm]

I made that statement due to the fact that there seems to be a lot of problems posted across the net regarding the K-x and sharpness. I previously owned Canon and Olympus cameras and must of been lucky not to have any problems.

This is a general problem with all cameras. And worse, it's an issue of camera and lens together. On my K-7, I have one lens at -8 at another at +4. Or maybe it's the other way around. Anyway, simply going to -8 overall would have made my other lens much worse.

I think the reason it's coming up now rather than earlier is simply that higher resolution sensors provide more to pixel-peep at.

I think it's a bit poor of Pentax to not have the per-lens setting in the K-x (and to leave the overall adjustment as a secret debug-menu option). They may want to save that to differentiate the high-end model better, but the real competition is of course the other companies.

[harleynitelite]

Are you sure this could be a lens problem? There have been many posts on here regarding mirror slap affecting pictures at certain shutter speeds that are suddenly cured when LV was utilized. I had a kx with this very issue and returned it.