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08-01-2019, 08:03 AM   #1
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"Catch in Focus" question

I use "catch in focus" quite frequently and successfully with many of my manual focus lenses, but occasionally I find the limitation of having only the central focus-point active to be a nuisance.


However, I've found, by accident, that a couple of my Sigma zooms, that have an AF/MF switch, will allow the camera to perform "catch-in-focus" when the lens is set to "MF" and use multiple focus points. The lenses in question are the Sigma 70-200mm f/2.8 and the Sigma 150-500mm f/5.6-f/6.3. Unfortunately neither of these is capable of close focus, 6ft and 7.5ft respectively.


I can envisage that "multiple-point catch in focus" could be advantageous in some circumstances, so my question is twofold :
a) does anyone else use this capability?
b) which lenses, ideally not quite as bulky as my two Sigmas and preferably with a degree of close-up if not macro capability, have an AF/MF switch?

08-01-2019, 11:02 AM   #2
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That last question is easy

Lenses with AF/MF Switch | PentaxForums.com

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08-01-2019, 11:41 AM   #3
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I also use CIF frequently and have lamented that I was limited to central focus point. Good to know that this works. I don't own a lens with the AF/MF switch, but I'll store that away.

CIF is a feature that I think clearly makes Pentax stand out above competitors. There are decades of amazing glass that is much more useful because of this. I have been shooting little league baseball with a MF Tokina AT-X 100-300/f4 that I bought for $120. I'd love an equivalent AF lens, but it would cost me 5 - 10x.
08-01-2019, 02:03 PM   #4
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QuoteOriginally posted by Adam Quote


Excellent Thank you for exactly what I was looking for (but had been unable to find)!

08-01-2019, 11:10 PM   #5
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QuoteOriginally posted by kypfer Quote
I use "catch in focus" quite frequently and successfully with many of my manual focus lenses, but occasionally I find the limitation of having only the central focus-point active to be a nuisance.


However, I've found, by accident, that a couple of my Sigma zooms, that have an AF/MF switch, will allow the camera to perform "catch-in-focus" when the lens is set to "MF" and use multiple focus points. The lenses in question are the Sigma 70-200mm f/2.8 and the Sigma 150-500mm f/5.6-f/6.3. Unfortunately neither of these is capable of close focus, 6ft and 7.5ft respectively.


I can envisage that "multiple-point catch in focus" could be advantageous in some circumstances, so my question is twofold :
a) does anyone else use this capability?
b) which lenses, ideally not quite as bulky as my two Sigmas and preferably with a degree of close-up if not macro capability, have an AF/MF switch?
i have the sigma tele macro 400mm,, works nicely with catch in focus, like you describe it. min. working distance for focus is about 150 cm.
08-01-2019, 11:29 PM   #6
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I have the opposite problem with K1ii. I try to set AF to spot, but feel that CIF reads from too large area. I have a much better hit rate with K30 when shooting sports. Too often K1ii seems to find a way to lock into background behind the target thought the center square stays on athlete. With fast moving subjects you really don't have time to see weather it locks on target or behind it while you shoot, so I've lost a lot of sequnces due to backfocus.
08-02-2019, 01:55 AM   #7
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QuoteOriginally posted by iheiramo Quote
I have the opposite problem with K1ii. I try to set AF to spot, but feel that CIF reads from too large area. I have a much better hit rate with K30 when shooting sports. Too often K1ii seems to find a way to lock into background behind the target thought the center square stays on athlete. With fast moving subjects you really don't have time to see weather it locks on target or behind it while you shoot, so I've lost a lot of sequnces due to backfocus.
With a manual-focus lens "back-focus" is not a problem, which can be the attraction of using it.


Envisage a butterfly (or pair of butterflies, to get optimistic) flitting about in a flowery glade lit by dappled sunlight. An autofocus nightmare, at least in my experience. However, fit a manual-focus lens, set it to the sort of range to give an appropriate image size of your subject in the viewfinder, then effectively wave it all about with the shutter button pressed (or park it on a tripod with the cable release locked down). When something flies into the pre-chosen range the shutter will fire Assuming the various other parameters such as depth-of-field, subject movement speed, sensitivity etc. have all been considered, something like an acceptable photograph may well be the result


With multiple focus points available to trigger the shutter, the need for having the subject absolutely dead-centre to trigger the shutter is eliminated!


No, I've not had a lot of success yet, but my incidence of "near misses" is a lot higher than it used to be, so I'm hopeful practice and a more suitable lens will improve things
08-02-2019, 08:02 AM   #8
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QuoteOriginally posted by iheiramo Quote
I have the opposite problem with K1ii. I try to set AF to spot, but feel that CIF reads from too large area. I have a much better hit rate with K30 when shooting sports. Too often K1ii seems to find a way to lock into background behind the target thought the center square stays on athlete. With fast moving subjects you really don't have time to see weather it locks on target or behind it while you shoot, so I've lost a lot of sequnces due to backfocus.
The actual size of the AF area in spot autofocus can vary between models

But if you find the camera is locking into the background and not the subject you are not using CIF correctly

CIF requires you to focus the lens and anticipate where the subject will be in focus. If you are focussing on the background that is hardly the cameras fault

08-02-2019, 01:21 PM - 1 Like   #9
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QuoteOriginally posted by pschlute Quote
CIF requires you to focus the lens and anticipate where the subject will be in focus.
That doesn't work in sports. If you prefocus, it's better to shoot burst without CIF. You get results much more reliably that way.

CIF is good when you don't know where the action is and you follow the target with center spot. Once I learnt the technique I got really good hit rate with K30. At best day about 90% were in focus. With K5 hit rate was about the same, but it didn't lock on target as well as K30. With K1ii I've been well below 50% when I expected it to perform even better, but I think it's best to lock on target. So where K30 didn't take a shot until I had correct focus on target, K1ii manages to lock behind the target if gets a slightest chance for it. But missed shots are worht the succesfull one's with K1ii I just wish I could set the focus to read only from within the small square in the center.

I mean shots like these taken with K1ii & M'300/4:







08-02-2019, 02:35 PM   #10
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QuoteOriginally posted by kypfer Quote
With a manual-focus lens "back-focus" is not a problem, which can be the attraction of using it.
If one is using the PDAF system (CIF or focus confirm) back-focus* is just as likely with a manual focus lens as with regular PDAF with an AF lens. That is one of the cautions that goes with both CIF and focus confirm; both focus accuracy and precision are no better than the PDAF system driving both techniques. If the lens provides an ambiguous image to the PDAF prisms, back or front focus or inability to detect OOF will be the result.

In other words, back-focus is not the same as the AF system locking on a background feature, though that is quite possible with a manual lens too, since sometimes the PDAF system will err on the side of calling fuzzy sharp if contrast is high enough. CIF is fine and can work quite well, but has few intrinsic strong points. As for the butterfly example, chances are that the insect will be OOF by the time the system reacts and releases the shutter. Be aware too, that the AF points away from the center points have much lower focus sensitivity (f/5.6 vs. f/2.8) meaning that using them is like assessing focus with a lens maximum aperture of f/5.6.


Steve

* By the usual definition, that being the focus system indicating an in-focus condition when the actual plane of focus is beyond the indicated point of focus.

Last edited by stevebrot; 08-02-2019 at 02:41 PM.
08-02-2019, 02:45 PM   #11
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QuoteOriginally posted by iheiramo Quote
That doesn't work in sports. If you prefocus, it's better to shoot burst without CIF. You get results much more reliably that way.
Yep, and similar applies to bird and wildlife photography; depending, of course on the subject, its anticipated motion, and kit used. The old school approach works amazingly well. CIF comes onto its own for certain types of macro photography with slow-moving subjects or when the photographer's vision is poor and when regular AF does not work well.


Steve
08-02-2019, 10:49 PM   #12
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I use it for macro and bug shots.
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