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10-30-2012, 03:14 PM   #1
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Can we add Focus-Bracketing?

When I used (pre K30) the Focus-Bracketing on my Bridge Canon, I assumed it was an advanced "DSLR thing" unusual to find on a P&S. So thought it'd be a function the KR - then changed to the K30 I actually bought - would have. Which it doesn't.

I keep reading of DSLR lenses having back and front focusing problems. With a testing or borrowed lens, Focus-Bracketing might adjust the focus-error to usable - or by adjusting the spread of the Bracketing - show where the error is - fore or aft, and by how much. Obviously - that's not what pro-level testers / adjusters would do, having advanced abilities and equipment - but not all of us have anything like those abilities or testing gear.

It would also be workable in ordinary use - while the K30 has very nice mag-up abilities in Live-View - and the Focus-Peaking - it can't, unlike my Bridge with EVF - "mag-up" the centre section of the Viewfinder to help with focusing. Often, particularly on tripod, as the K30 LCD doesn't tilt, you can't use it in sunlight - you still need to use the Viewfinder. Certainly - the K30's AF works extremely well - the accuracy and speed is amazing, if you're used to Bridge cameras! However - that doesn't work too well with the manual lenses I really bought the K30 for.....

Sure, the MF is very good indeed - but the "further out you go" - the more awkward to get "right-on" with Viewfinder. Being able to Focus-Bracket - with adjustable distances "fore and aft" - as my P&S Canon does - would result in more 'keepers'. F/B isn't an AF function in that camera - it's MF only. I did wonder if DSLRs could combine F/B with AF, not just MF - but it seems, at least in K30's case, they don't do either.

It would seem that - when you can see the K30's LCD - even with Live-View mag-up and the Peaking - being able to Bracket a shot, maybe with the shortest fore-aft adjustment, it would fine-tune the accuracy. Or for moving targets - widen out the Bracket spread a bit to allow for changing distance.

Focus-Bracketing probably isn't a function the Pros would want to use - as they get long-distance and fast-moving targets in tack-sharp focus, first-time, every-time - but not everyone is that good - and I'm certainly not with cooo-eee of it...!

For DSLRs like the K30, where the makers put in dozens of Scenes, Automatics, and Filters modes, to help the newer users - which certainly aren't 'Pro level' functions - Focus-Bracketing would be a huge boost to usability and results.

It would also increase Pentax popularity, because it assists usage of all the K-mount manual focus lenses from K-series to A-series, even if some wouldn't want to go back to the M42s. And that's based on my own experience - assuming that K-R, then K30, would indeed have Focus-Bracketing.

Could it be done with a firmware update? The camera already does Bracketing - so could it be added alongside AEB?

Regards, Dave.


Last edited by exwintech; 10-30-2012 at 03:25 PM.
10-30-2012, 03:19 PM   #2
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I've been asking for this for years. It's amazing to me they havn't done this yet.
10-30-2012, 03:29 PM   #3
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Yes
I have just ordered a little robotic drive to partially automate focus stacking optically by the rack on my Pentax Bellows M.
I think why the camera manufacturers did not do it in camera is that the computing power to do a contrast focus stack is far beyond the little battery powered picos.
I am using Hugin on linux 64 with a sandy bridge,
10-30-2012, 04:00 PM   #4
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Wombat2go - Er, by that, do you mean the K30's "computing power" isn't up to Focus-Bracketing...?

I hadn't realised that my 2008 P&S Canon SX10 has more "computing power" than a K30... (Might surprise both Canon and Pentax, too...)

I'm not talking about "contrast focus stacking". That's clearly an advanced operation.

By Focus-Bracketing - I mean just 3 images - one where focused - one a bit closer, one a bit further - spread range adjustable - which my SX10 does rather neatly and very usefully.

How the spread is set, is shown here - and works in any mode from Program to Manual, but in MF only.
Canon SX10 Manual, Page 130 - "Focus Bracketing (Focus-BKT Mode.)"

(attrib. Canon Australia)



Regards, Dave.


Last edited by exwintech; 10-30-2012 at 04:07 PM.
10-30-2012, 05:41 PM   #5
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I think this is a feature they should add. Yes, most people won't use it, but most people also don't use HDR (exposure bracketing), video mode, etc. There are many modes that are in there but people don't really use them. This one would actually have a use, especially for macro shooters.
I think the reason there is no focus bracketing is because it would be hard to communicate to the camera "how much" of a difference you want.
10-30-2012, 07:32 PM   #6
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Na Horuk - As with a DSLR the lens focal lengths / DOFs can change from lens to lens, I agree - you couldn't tell the camera - "As set - with -40mm and +40mm" or, "As set - with -40cm and +40cm" - closer and further than the 'Set' focus, so on.

What you could do - as the SX10 does, but more refined for a DSLR - is say "amounts". Where the SX10 - see screenshot above - has 3 settings - 1. Close to 'Set', 2. Further from 'Set', 3. Much further - you could have 5 settings, with "1" just a few millimetres each side of 'Set' - to suit precision lenses with very shallow DOF - then "2" to "5" at multiples or increments of the "1" distances from there.

You would need to learn for each lens just how far in physical distance each of the 5 settings were from the Set focus point. And allow for DOF increasing as aperture decreased.

With the SX10 - the "amounts" of those 3 settable distances fore-and-aft do vary with amount of zoom used. Once you've been using F/B for a short time, you learn to "allow" an amount with length of zoom. Starting with the middle "2" until you find out what it's doing.

Close in, 'Wide End', or Macro - "1" works best - but at long zoom, where it's more-or-less infinity - use "3", because it's easier to be further off with a Bridge zoom on MF.

Sadly - there's nothing like it to "MF compensate" with Macro-Video - that's very much a case of learning what "looks right" and adjusting from there.

Also - if you're saying that "most people" don't use video in a DSLR - which is likely true of those at your experienced level - the two questions I'm getting most from friends about the K30 are - "Does it take nice bright sharp pictures?" - Yes, it does, if the person driving it does...

And - "Does it do really good video with clear stereo?" - No, your SX40, HS20, FZ150, etc - will totally clobber the K30 for video... Superb camera, the K30 - astounding if ones are used to P&S - but if you get a K30 - take your SX40-etc-etc along to do the video - as I'm doing with my HS10.

So at least with the folk thinking of moving up to entry or bit above DSLR - the quality of HD Video - AND the Stereo Audio - rates very highly in their interests. Of 7 friends here - 3 are thinking of buying a DSLR 'soon' or 'for Christmas'.... None will be buying a K30 - let alone a K-R "that doesn't even do proper H264/MOV...".

Regards, Dave.
10-30-2012, 08:17 PM   #7
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Not sure how any camera could do this with manual focus lenses which is what the OP is suggesting he wants this feature for. The F/B Adlustment in dSLRS is not moving the sensor forwards or backwards, but making small adjustments to it deems to be in focus and to what it is communicating to the lens focusing motor. And the camera cannot control a manual lens focussing. Not possible without an external system like Wombat2go is trying to build, which would ned calibration lens by lens in any event.

With chip enabled autofocus lenses it may be possible if the lens chip would provide sufficient information to the camera's processor. But if lens chips don't currently provide this, then a whole new generation of upgraded lenses would be required. Can't see that any time soon.
10-30-2012, 08:34 PM   #8
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QuoteOriginally posted by exwintech Quote

It would also increase Pentax popularity, because it assists usage of all the K-mount manual focus lenses from K-series to A-series, even if some wouldn't want to go back to the M42s. And that's based on my own experience - assuming that K-R, then K30, would indeed have Focus-Bracketing.

Could it be done with a firmware update? The camera already does Bracketing - so could it be added alongside AEB?

Regards, Dave.
I'm not sure what you mean by focus bracketing with manual lenses. Are you envisioning an added mechanical device that rotates the focus ring on the lens so you don't have to do it with your fingers? It's not all that uncommon for people to do focus bracketing manually on SLR's.

For auto-focus capable lenses, I've often thought it would be both a good feature and relatively easy to implement.

10-30-2012, 10:35 PM   #9
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Cfraz / Southlander - From what you folk are describing, the Canon P&S must have an additional function that DSLRs don't...

That is - it's doing it in a different way when using MF. Put the camera in M-Manual Mode, and turn off the AF by selecting MF. And it does Focus-Bracket at that setup. I'm not "misreading" the SX10 Manual - I use it often. It's a Bridge-Zoom - meaning, often you have to put it in Manual Mode to persuade it to do do what YOU want it to do, YOUR way...

But - I'm not insisting that Focus-Bracketing has to be in Manual Mode - and it is apparently "do-able" in DSLRs. Which is why I assumed that the K30 would have the function.

Possibly why others above are also indicating that they'd like the function in Pentax DSLRs....

Or maybe we just need a "hack" (apparently not related to CHDK) like this one a chap has created for Canon DSLRs:

Quote: - "DSLR Bracketeer is a simple program I made for controlling CANON EOS DSLR cameras. It is used for focus bracketing on for your Canon DSLR...." End quote.

Ref: - DSLR Bracketeer by Milos Paripovic


Regards, Dave.
10-31-2012, 01:45 AM   #10
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Part of the confusion is the loose use of the term "manual" here. It could refer to taking a camera off its Program setting where it decides everything, in P&S cameras this is often the "Manual" function; turning auto-focus off, ie "manual" focus but still using AF capable lenses; or in context of older non-AF "manual" lenses eg Pentax M or A series. I think the OP has used the term "manual" in more than one of these contexts which is somewhat confusing this discussion.

I stick by my comment that "Not sure how any camera could do this with manual focus lenses" which I made in context of refering to non AF lenses eg Pentax M or A series lenses or similar. There is no way the camera can drive focus changes on manual lenses. I made the comment in response to the OP stating "However - that doesn't work too well with the manual lenses I really bought the K30 for.....".

Reading the above post, it seems DSLR Bracketeer is a home-spun tethering program, and programming interface code is available for Canon cameras to instruct an AF lens to change focus by defined increments, which the software author has taken advantage of. I'm not at all familiar with tethering for Pentax and whether (1) the interface coding syntax for Pentax is readily accessible by enterprising home programmers, (2) whether a software function to move the lens in defined steps from its starting point is accessible by external tethering software and (3) which Pentax cameras are capable of tethering control. Interesting little program though, I must say.

A bridge camera has a distinct advantage here - the one fixed lens means that software encoder knew exactly how many turns of the focus motor are needed for a given amount of throw of the lens and can therefore program known changes of focus. This would be then quite easy to build in as a standard function. With interchangable lenses with different focus throws, every lens will be different and impossible to program for unless a modern lens with an inbuilt chip is used and the chip has this data and can pass it to the camera. Presumably cameras have a minimum unit of turn for focus that could be used, but may produce variable results by lens and might be in painfully small steps.

Last edited by southlander; 10-31-2012 at 01:52 AM.
10-31-2012, 03:08 AM   #11
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QuoteOriginally posted by exwintech Quote
Na Horuk - As with a DSLR the lens focal lengths / DOFs can change from lens to lens, I agree - you couldn't tell the camera - "As set - with -40mm and +40mm" or, "As set - with -40cm and +40cm" - closer and further than the 'Set' focus, so on. What you could do - as the SX10 does, but more refined for a DSLR - is say "amounts". Where the SX10 - see screenshot above - has 3 settings - 1. Close to 'Set', 2. Further from 'Set', 3. Much further - you could have 5 settings, with "1" just a few millimetres each side of 'Set' - to suit precision lenses with very shallow DOF - then "2" to "5" at multiples or increments of the "1" distances from there. You would need to learn for each lens just how far in physical distance each of the 5 settings were from the Set focus point. And allow for DOF increasing as aperture decreased.
Maybe. The thing is, P&S and bridge cameras have a fixed lens, so the manufacturer can expect its AF and DoF. With a DSLR the camera will have a hard time figuring out how big the focus throw is, for example. And then combining that with focal length and other factors.. basically, the feature would be unreliable. You could learn how it works for specific lenses, though. Most people would only use this with one or two of their lenses, anyway.
10-31-2012, 04:32 AM   #12
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Southlander - Sorry, I was being sarcastic, there... Read in context, I said - "Certainly - the K30's AF works extremely well - the accuracy and speed is amazing, if you're used to Bridge cameras! However - that doesn't work too well with the manual lenses I really bought the K30 for....."

The comment was a joking reference to the K30's having very good AF - but which doesn't "work well" - with full manual lenses. I should have added a couple of Smilies after that comment...

Yes, I do know - there's a Tak SMC 55mm f/1.8 on my K30 at present - using the excellent, as-new, genuine 'Pentax-Japan' Adapter I just bought from 'Ddhytz' on this forum, after a run-in with a semi-jamming rather crude clone. Actually the Tak is on the camera along with a 1973 vintage M42 APS Auto Teleplus 2x TC my landlord gave me... No, I don't think I'm quite going to make the cover of "Nat Geo" by trying to convince the otherwise very neat little 55mm Tak that it's a 110mm lens - but I'm just having fun...

It's evening in Sydney now - but tomorrow I'm going to see just how much the Tak "55/110" improves my K30's Video....

That's "fun", y'see - I do have a somewhat warpy sense-of-humour....

Regards, Dave.
10-31-2012, 05:37 AM   #13
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No probs. Took you literally. I am growing fond of using manual lenses as they force you to properly think about what you are doing. Auto everything and its easy to snap away with little thought as to what that a particular photo is intended to achieve. You can see I've developed a bit of a thing about M series lenses, and about to start a month of Single in... with my M85! And with work commitments, 4 of those days are going to have to be Sydney subjects.
10-31-2012, 05:42 AM   #14
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Interesting that you are using a 2X teleconverter. I just did a shot yesterday (for LF forum) comparing a 2X with a "real" lens

SMC Pentax -M 1:2.8 100 mm at f/2.8 and 500th
https://www.box.com/s/ju9wiluwj57kimdlnx5f

SMC Pentax -A 1:1.4 50 mm with a Vivitar 2X_22 TC, lens at f/1.4 and 500th
https://www.box.com/s/bdwhdpz73x3fj28zmsqd

The camera was at fixed distance on a tripod for both shots.

The camaera was not able to give Focus Indication through the 2X TC, and as can be seen the 2 X TC image is not sharp through the DOF compared to the "real" lens
Also the colors are degraded by the TC.
My old TC looks OK visually except the glass is a slight pale yellow color. Maybe it has reached its use by date , or is this typical of a 2X TC ?
10-31-2012, 05:49 AM   #15
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I get the impression from reading on the net that 2x generally is a bit too much magnification for good results. A 1.4x seems more likely to preserve reasonable image quality. For AF, the 2x is taking away two stops of light and if sharpness is poor, contrast will also be suffering. Collectively sounds like its all too much for the AF to get a good lock.
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