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07-13-2012, 05:13 PM - 1 Like   #1
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K-30 AF Accuracy Testing for the Pentaxforums Review: Give Us Your Ideas!

Hey guys,

So I'm the sucker who's currently writing the K-30 review for the site. Yes, send all your hate mail my way once it's posted.

I'm currently getting down to the final bits of testing, on the way to publishing the review early next week. We've done AF speed tests and some field shooting, but we still have to work on AF accuracy tests. We're wondering if any of you have any fun, creative, interesting ideas for how to test AF accuracy. While we have our own standard tests, this review is primarily for you, the readers, so we'd love to know what you'd test if you were in our shoes (i.e., if you had a K-30 in your hot little hands). So, please feel free to post your ideas in this thread. If we end up using them in the review, we'll give you a shoutout in the review text (unless you don't want us to)!

Any and all ideas are welcome, though we'll only be selecting the best two or three of them (among those that are actually feasible to perform).

Some notes to take into account when devising your devious schemes:
- I live in the desert!
- I have the following AF lenses: DA 15, DA 21, FA 31, DA 35, FA 43, FA 77
- I have tungsten, CFL, and regular fluorescent lights in my house.
- I have cats, which can be very tricky subjects to shoot.
- We want to test the K-30 against the K-5.
- I don't have a flash, aside from the built-in ones on the K-5 and K-30.

And I might add more items to that list as your ideas expose more holes in my plan.


Last edited by deadwolfbones; 07-13-2012 at 05:55 PM.
07-13-2012, 05:24 PM   #2
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Behavior with flash, haven't there been issues reported with hot shoe and off camera flash sync on the K-5?
07-13-2012, 05:31 PM   #3
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As a general suggestion, what, in your experience, is the D700 good at, and the K-5 not, in terms of AF? Test whatever that may be with the K-30.

Also some tests to try and identify the narrowness or tightness of the centre-spot AF would be useful. For some shooting scenarios (birds amidst foliage, focus on specific players in a team, the fabled 'focus on the eye' for portraits etc) it would be useful to see how tight one can go with just one AF point like the centre one.

You may also like to do some tests equivalent to those Falconeye did on the D800 to identify the weaknesses or variable sensitivity of the various sensor points/zones across the K-30's AF matrix.
07-13-2012, 05:36 PM   #4
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Take whichever AF lens has the longest focus throw (FA 77?) and try to track a moving object (car or bird, cats are erratic enough) with AF.C

I'd personally prefer to see the AF.C accuracy results from a slow-poke AF lens like the DA*50-135mm, but I don't think you'll wait for me to ship mine to you...

07-13-2012, 05:37 PM - 1 Like   #5
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Focus tracking.

The dog-running-toward-you test is always good. Dogs are pretty fast.

For extra credit, focus on a black dog. In the dark.

On a slightly more serious note, my K-5 seems to have the dreaded PDAF low-light front-focus problem. On the K-30, I'd like to see the results of a series of shots of the same still-life subject at various light levels, using a dimmed lamp for example.

Using an f/2.8 lens wide open, start with maximum brightness, focus to infinity, autofocus on the subject, take a shot, watch the meter while you dim the light 1/2 stop (or whatever), then focus to infinity again, autofocus, shoot, dim, repeat ad nauseum.

Does focus remain consistent? If not, at what exposure values does it start having trouble?
07-13-2012, 05:45 PM   #6
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QuoteOriginally posted by Quicksand Quote
On the K-30, I'd like to see the results of a series of shots of the same still-life subject at various light levels, using a dimmed lamp for example.
Something similar to this was done here:
https://www.pentaxforums.com/forums/pentax-k-30/192301-k30-tungsten-light-test.html

Imaging Resource also do TONS of these sort of test shots under variable light levels (eg the ISO vs Lux light level test image matrix down the bottom of this page that was part of their K-5 review). It's something to look out for once they complete their K-30 review.
07-13-2012, 05:53 PM   #7
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QuoteOriginally posted by Docrwm Quote
Behavior with flash, haven't there been issues reported with hot shoe and off camera flash sync on the K-5?
Alas, I don't have a flash.

edit: aside from the built-in ones, of course.
07-13-2012, 05:54 PM   #8
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QuoteOriginally posted by panoguy Quote
Take whichever AF lens has the longest focus throw (FA 77?) and try to track a moving object (car or bird, cats are erratic enough) with AF.C

I'd personally prefer to see the AF.C accuracy results from a slow-poke AF lens like the DA*50-135mm, but I don't think you'll wait for me to ship mine to you...
Yep! In my experience, whenever I walk into a room with a camera and sit down to try to take pics of my cats, they immediately run towards me. So, if you could see if the K-30 AF.C can track them as they move towards you, that would rock!

Thanks for doing the review, really looking forward to it!

07-13-2012, 06:00 PM   #9
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QuoteOriginally posted by deadwolfbones Quote
Alas, I don't have a flash.

edit: aside from the built-in ones, of course.
Perhaps one of the strobists here would be willing to loan a good one for the sake of the review? I would but I don't have pTTL model.
07-13-2012, 06:08 PM   #10
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QuoteOriginally posted by Docrwm Quote
Perhaps one of the strobists here would be willing to loan a good one for the sake of the review? I would but I don't have pTTL model.
Would have to be overnighted by Monday to meet the pub date. :/

I think we'll have to skip that test and maybe do a followup, or one of our strobists can do so independently, later on.
07-13-2012, 06:13 PM   #11
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QuoteOriginally posted by deadwolfbones Quote
Would have to be overnighted by Monday to meet the pub date. :/

I think we'll have to skip that test and maybe do a followup, or one of our strobists can do so independently, later on.
Fair enough, thanks for asking for ideas. I was trying to go with something other than the AF. Looking forward to the results!
07-13-2012, 06:21 PM - 1 Like   #12
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Would love to see a review of the cats. They are generally quick to focus and track moving objects well. However, they can generate a lot of noise, and the output always stinks.
07-13-2012, 07:01 PM - 1 Like   #13
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I would be interested in the low light autofocus capabilities, at pedestrian speeds...not cat speed.
07-13-2012, 09:10 PM   #14
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brainstorming ideas:

- set up cones on the ground over different distances to check mid to long focusing and apertures.

- different distances of objects with light and dark coloring, some with little contrast.

- focusing accuracy while panning

- while shooting live action, like an equestrian training center

- different parts of stands of a stadium, like a baseball game, sunlit and shadow

- macro accuracy objects with ruler next to them
07-14-2012, 12:10 AM   #15
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Show us how big the centre AF sensor is relative to the VF markings.

Is the AF accurate in the dark using the af assist light and pop-up flash (so there's an image to look at!).
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