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12-08-2013, 04:52 AM   #1
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New K-50 user... Some questions

Hi lads and ladettes,

I've just received my shiny new K-50+DAL 18-55mm WR (my first dSLR though I used to do a lot SLR work in the old days, with film). Updated firmware to 1.01, read the manual and played around a little. So far, I'm quite impressed with the IQ (my other current cam is a Fuji X10 which is not bad at all but can get rather nasty above ISO800.)
Unsurprisingly I've got some questions (I've searched the forum and found answers to some other questions I had). So here goes:
  1. Exposure bracketing: I can't get more than +- 3 EV, in the various photo capture modes (I'm not using the Auto or SCN modes). The display seems to imply I can do +- 5 EV, and the manual says nothing about such a limitation (or I haven't found it).
  2. If I leave the AF mode set to Face Detection in LiveView and there are no faces around to focus on, what is the camera's Plan B? Center spot or some other mode? (I tested that and found that the green focus rectangle appears at various places. There's certainly a logic there, but I don't see it yet.)
  3. What, if any, is the received wisdom re the D-Range settings (ie Highlight Correction and Shadow Correction )? Leave them at default or change, and if so, how and why?
  4. And what about the Noise Reduction settings (High ISO NR and Slow Shutter Speed NR)? Leave them as they are or change?
  5. I am not totally sure that the focussing is 100% spot on. Even when I am using f/8 or F/11 the picture doesn't seem to be absolutely sharp (pics taken with ISO100). Would it be useful to run a few tests, playing with the AF Fine Adjustment?

Well, that's it for now. I am sure I'll have some more questions when I really start using the thing;-)

Thanks for any hints or help...

Jon

12-08-2013, 05:01 AM   #2
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5. Post samples
4. I left Slow shutter NR to Auto and High ISO NR to Custom, ISO =<1600 Low, above Off. I found that the NR sometimes caused a color shift.
3. Depending on the environment and lighting, the DR expansion stuff can cause a LOT of noise, so I just leave it off.
12-09-2013, 04:17 AM   #3
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Thanks for your answer.
QuoteOriginally posted by Giklab Quote
5. Post samples
I will look into this further and do some controlled tests. I'll post some examples if I think the AF is indeed slightly off.
QuoteQuote:
4. I left Slow shutter NR to Auto and High ISO NR to Custom, ISO =<1600 Low, above Off. I found that the NR sometimes caused a color shift.
Interesting. Normally I'd expect High ISO NR to be used *especially* in situations where ISO is 1600 and above.

I am still puzzled by the +- 3 range of the exposure bracketing option.
12-09-2013, 06:46 AM   #4
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Well, due to the color shift (images get a bit yellow) I don't use much NR except below ISO 1600 (above that the camera applies the equivalent of Low NR to everything anyway). Low to me seems to only remove colour noise, which doesn't impact detail at all. And at monitor/web sizes noise isn't actually visible until ISO 6400.

Although I'm in the middle of experimenting with JPEG settings, so I might change my preferences.

12-09-2013, 06:52 AM   #5
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Also, RE: exposure bracketing: You can go +-5EV including exposure compensation.
3 images
+-2EV
+-3EV comp
12-09-2013, 06:54 AM   #6
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The + -3 exposure is interesting… but I've personally never gone above +-2 with any kind of decent results. Usually I'm just looking for the right exposure. There's enough DR in the images that HDR is usually un-necessary (on K-5 series cameras) and often doesn't look as good as a good exposure that's been post processed to maximum advantage. I'd hope you can get your exposure closer than +-3, that's a 6 stop range. So, I'm really interested in what you shoot. It's just one of those things I haven't heard anyone complain about before, and the K-5 style system has been out for 3 years now with thousands of posts about it.

You must shoot some really demanding stuff. I'd be interested in seeing some of your finished work.

Last edited by normhead; 12-09-2013 at 07:07 AM.
12-09-2013, 10:23 AM   #7
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QuoteOriginally posted by Giklab:
Also, RE: exposure bracketing: You can go +-5EV including exposure compensation.
Yeah, I did suspect that perhaps the scale is +-5EV with bracketing only supporting +-3EV because bracketing and compensation can be combined. I used to do that on the X10 because there exposure bracketing only supports a feeble +-1EV (OTOH the X10 supports ISO bracketing which I found sometimes quite useful).
QuoteOriginally posted by Normhead:
You must shoot some really demanding stuff.
Not at all;-)
I was just exploring the camera (after all, it's a new toy!) and the manual and saw that the EV scale runs +-5 while the bracketing stops at +-3. As the manual says nothing about the actual bracketing range, I thought I'd ask.
I sometimes take shots of bright church windows and surroundings where EV compensation and +-2 bracketing can be useful. But like you I've never really needed more than that.

As to the AF thing, I've discovered that the K-50 consistently produces slightly sharper images with Contrast AF (ie in LiveView) than with Phase Detect (ie through the viewfinder). I'm not really sure why that would be the case.
Never having used a dSLR before I am also bit nonplussed as to the usefulness of having 5/11 AF points. In bygone days, with my SLRs I'd split-image focus for the centre and then simply recompose the shot and I'm still doing that today. Old habits...
12-09-2013, 10:52 AM   #8
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Contrast AF is more accurate, because it reads data directly from the sensor (PDAF uses a separate sensor that can be a bit off). Try to calibrate your lens.
Multiple AF points are useful for continuous tracking and better compositions since the plane of focus shifts when you recompose.

12-10-2013, 05:00 AM   #9
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QuoteOriginally posted by Giklab Quote
Contrast AF is more accurate, because it reads data directly from the sensor (PDAF uses a separate sensor that can be a bit off). Try to calibrate your lens.
I would have never thought of that but it sounds logical.
I've downloaded some focus charts and played a little with the AF Fine Adjustment and there's indeed some mileage there. (Mind you, I am really picking nits... the Contrast AF output has been crisp and clear all along.) I'll post some 100% crops later.
QuoteOriginally posted by Giklab:
Multiple AF points are useful for continuous tracking and better compositions since the plane of focus shifts when you recompose.
Hm... it'll take a while to get used to these things, I suppose. Fortunately, most of the stuff in front of my lenses tends to be stationary (landscapes, insides of old, dark buildings etc), so continuous tracking is not something I'll have to use very often. (Having said that, I include a shot I took earlier this year in India, though that used MF mode.)
Thanks for your help, really appreciated.
Attached Images
 
12-10-2013, 06:17 AM   #10
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New Glass?

Hello Jon, Welcome to the Forum!
You've gotten some good advice already, hope it answers your concerns.
I'd like to address your question # 5, regarding 'ultimate sharpness'. It may not be focusing errors you're seeing, it might be the lens.
The DA 18-55mm is pretty good for what it is, but let's face it. It's a 'kit' lens, a starter lens, one of the better ones, no doubt. If you're used to seeing film shots taken with a prime or better zoom, it just won't match up.
But there's an upside. Used within it's range, it can produce some fine photos and is very handy for walk-around, general purpose use. Having WR and a compact size + weight make it useful tool.
Try to stay away from shooting wide-open (aperture), you'll find it's soft in the corners. It's better at the wide end, 50-55mm isn't nearly as sharp. Don't shoot at slower hand-held shutter speeds, it's far better to have an ISO 400 shot that's razor sharp than an ISO 100 version with a tiny bit of shake/blur.
This last point was a difficult lesson I had to learn coming from a film background. Once you loaded a roll of ISO 100, you had to work around that (and the resulting slower shutter speeds) for 36 exposures. When the light changed, you had to make other adjustments.
Not any more! Change the ISO between shots if need be, again, any camera shake, even the slightest bit, will make a good lens look bad.
Stay within the limitations of your gear, use it to advantage and your results will be impressive.
Last suggestions; If you don't have one already, start looking for a good post-processing app. LightRoom is the best (IMO) but not cheap. Gimp, FastStone and Picasa are free and serviceable.
Good luck!
Ron
12-10-2013, 09:39 AM   #11
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There's one last thing about AF which might be relevant (or not at all, but anyway): With the AF adjustment, 0 may not be the same as 'off'. For example, my 35/2.4 is actually at +4/5 with microadjustment 'unset'.

Speaking of this lens, you should really try to get it (mine was only 100€ second hand). A no-brainer with regards to price vs performance if you ask me.
12-10-2013, 10:01 AM   #12
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QuoteOriginally posted by BorrowedTime Quote
I am still puzzled by the +- 3 range of the exposure bracketing option
First select the exposure compensation you want to centre your bracketing around, it doesn't have to be 0 EV. Then you can change the amount of EV applied to each bracket, up to +/- 3.0. The maximum amount of exposure compensation is +/- 5.0.
QuoteOriginally posted by BorrowedTime Quote
I'd expect High ISO NR to be used *especially* in situations where ISO is 1600 and above
That's my understanding as well, and it seems to work when I've shot sports in low light in TAv mode and the ISO has been between 5000 and 6400. What NR and SR can't do is compensate for poor focus. With the DA L lens, you don't have quick shift focus and getting the right subject in focus can be a challenge (at least for me.) Master focusing, and your other problems will probably diminish. If I ever get to that point myself, I'll be happy to share my technique.
12-10-2013, 11:48 AM   #13
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I'd just like to comment on the excellent photo you posted, OP. The car reminds me of one of those tin toys.
12-10-2013, 12:40 PM - 1 Like   #14
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Regarding contrast AF vs phase detect AF, the former is only more accurate when the system is not calibrated. Once you do the AF fine adjustment correctly you can actually get sharper focus with PDAF. The exception is of course zoom lenses since sometimes they will need different AF fine adjustment for different focal length - in that case CDAF is indeed the better option.

The reason for CDAF not being as accurate as PDAF is that the sensor is operated at reduced resolution in live view, even during focusing. Just the same as it does in video, reading only alternate lines, or even 1 in three lines. So in practice the AF algorithm is seeing an image of much lower resolution that the actual picture that will be shot. The focus would indeed be perfect for a low resolution shot but not enough to make full use of the sensor's resolution.

The PDAF sensor on the other hand almost always has pixels that are smaller than that of the image sensor and therefore have the potential of achieving an even better focus than the sensor could at full resolution, 'even' better is in the end no better than 'as good as'. All this of course goes out of the window if the AF is not properly calibrated.

Depending on which camera (I don't know the specifics) it is sometimes the case that the horizontal resolution is used fully but never the vertical.
12-10-2013, 12:45 PM   #15
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Edit to add: apart from the PDAF pixels being smaller, even if they weren't smaller they could still achieve sharper focus because they rely on a different principle for achieving focus - the system measures parallax between two sets of sensors rather than trying to achieve high contrast in the image that falls on the sensor. The parallax shift is normally much larger than the spreading caused by soft focus and therefore more easily detectable for a given amount of defocus.

Here's an example (you will need to view the full size image as the difference doesn't show up in the reduced image below):
Both images are autofocus, the Image on the left focused in live view while the right is with the viewfinder.
Both are shot with Tamron 90mm macro at almost the closest focus distance at F8, ISO 100, 1/180 with flash. Both have exactly the same PP applied, mainly sharpening and some levels adjustment to reveal details in the less lit areas.
They are shot with K-3 rather than K-30 but same principles apply.

Click for full size 100% crop image




PS: Anyone recognise what it is ?

Last edited by lister6520; 12-10-2013 at 02:44 PM.
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