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10-01-2016, 12:06 PM   #1
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K-1 AF - does it get better?

So after few weeks with K-1 I have definitely noticed not-so-stellar AF performance with the SMC 50 1.8 prime. I haven't tried any other AF lenses yet, so wanted to ask if more modern lenses (D FA zooms for example) are significantly better at focusing with K-1? My hit rate is definitely lower than with my previous mft body (and mirrorless are supposedly worse at focusing than dslr's, at least before a6300 and x-t2 were released). I'm not trying to lit fires, I love K-1's image quality and many other features, I just want to know if AF would be better with other lenses. I'm just starting to build my collection now.

Thanks

10-01-2016, 12:12 PM   #2
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I noticed a big improvement on my 55mm 1.4 when I jumped from the K3 to the K1. The DFA 70-200 also focuses faster on my K1 compared to the K3.

My only screw drive AF is the 35 2.4 which is quite snappy on the k1
10-01-2016, 12:25 PM   #3
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QuoteOriginally posted by awscreo Quote
not-so-stellar AF performance with the SMC 50 1.8 prime.
That's a pretty generic statement for a 50mm screwdrive lens. What do you mean by performance? Speed? Accuracy? Tracking?

Last edited by biz-engineer; 10-01-2016 at 12:32 PM.
10-01-2016, 12:36 PM   #4
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With an aperture set at 1.8, the depth of field is super narrow, especially on full frame. If by 'performance', you mean missing focus, this may be the reason.

10-01-2016, 12:37 PM   #5
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Awscreo, as Kenspo points out, the new D FA f2.8 zooms are perfect for the K-1. Save your pennies.😀

But I've used both the DA50 and its sibling the DA35.

Care to post photos that illustrate your problem?
10-01-2016, 12:40 PM   #6
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I noticed a improvement over the K-3 with the DA560 for birds in flight but I still miss shots because it wants to focus on trees or rocks in the back ground.

With bif coming directly at me it's very difficult to get it to focus unless there's a clear sky behind the bird. It can be very frustrating when you have a chance to get a eagle or osprey coming in towards you to grab a fish in the river and all the camera wants to focus on is the rocks on the other side of the river.

I have no experience with other brands so not sure how well they do. I am still very happy with the K-1's performance, it is better than the K-3 and I have been able to get some good shots when birds are going in from side to side.
10-01-2016, 12:40 PM   #7
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I can't comment on the K-1 but the 50mm 1.8 focuses pretty poorly on my K-3, unlike the 35mm 2.4. The focus ring on the DA50 is a little long imo, which probably causes the performance "issue" you speak of.
10-01-2016, 02:07 PM   #8
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QuoteOriginally posted by KiloHotelphoto Quote
I noticed a improvement over the K-3 with the DA560 for birds in flight but I still miss shots because it wants to focus on trees or rocks in the back ground.
But you need to keep your selected AF point on the eagle, KiloHotelphoto ... it must be straying over the background. Remember since you have the K-1 and K-3 turn on AF Hold (say, to Medium) so it will forgive you every now and again when you make a mistake.

10-01-2016, 02:40 PM   #9
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My main issue is accuracy. Speed is on a slow side, but it's understandable due to the smc motor. Basically, in good day light conditions, I'd be focusing on things 2-3m away from me and would miss focus at least half the time at 2.8, which isn't that shallow, comparable to 25 1.4 i used on my mft setup. I mean i get that the lens is cheap, and if more expensive and newer models perform better, I'm ok with a 100$ lens having af issues. I mean at least optically it's very good for the money, so I consider my money well spent. I got few suggestions regarding tuning the af of the lens, and I will certainly do that too. But sometimes i'd nail focus from first attempt, then try to focus to the exact spot again and get 3 misses in a row (meaning focus missed by a bit, not complete miss like focusing on a background).

---------- Post added 10-01-16 at 02:41 PM ----------

QuoteOriginally posted by Ron_Man Quote
I can't comment on the K-1 but the 50mm 1.8 focuses pretty poorly on my K-3, unlike the 35mm 2.4. The focus ring on the DA50 is a little long imo, which probably causes the performance "issue" you speak of.
That might be it. I mean it's a fairly cheap lens and I wasn't expecting pro grade results. I mainly want to know if actual pro grade lenses perform significantly better (faster/more accurate)

---------- Post added 10-01-16 at 02:42 PM ----------

QuoteOriginally posted by clackers Quote
Awscreo, as Kenspo points out, the new D FA f2.8 zooms are perfect for the K-1. Save your pennies.😀

But I've used both the DA50 and its sibling the DA35.

Care to post photos that illustrate your problem?
I'll try to shoot a sequence of shots when I have time to illustrate the hit rate. Need to think of some sort of methodology to keep it semi-consistent.

---------- Post added 10-01-16 at 02:43 PM ----------

QuoteOriginally posted by biz-engineer Quote
That's a pretty generic statement for a 50mm screwdrive lens. What do you mean by performance? Speed? Accuracy? Tracking?
Mainly concerned with accuracy
10-01-2016, 04:02 PM   #10
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QuoteOriginally posted by clackers Quote
But you need to keep your selected AF point on the eagle, KiloHotelphoto ... it must be straying over the background. Remember since you have the K-1 and K-3 turn on AF Hold (say, to Medium) so it will forgive you every now and again when you make a mistake.
I will give that a try, got about six to seven weeks until the eagles really start to show up in the hundreds. Hopefully I will be able to get some shots to share.
10-01-2016, 04:59 PM   #11
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QuoteOriginally posted by awscreo Quote
That might be it. I mean it's a fairly cheap lens and I wasn't expecting pro grade results. I mainly want to know if actual pro grade lenses perform significantly better (faster/more accurate)
Unless something has changed the DA 50/1.8 is not on the list of official FF compatible lenses, though some users are happy with its performance on the K-1. My experience on 35mm film is that the lens has significant vignette unless stopped down and is noticeably soft in the corners. Whether the corner softness is due to field curvature, I did not explore.

My conclusion was that I have better fast 50s in my bag for shooting 35mm film and if I had a K-1, the DA 50/1.8 would not be in the bag, but it would not be due to deficiencies in its AF performance.

QuoteOriginally posted by awscreo Quote
I'll try to shoot a sequence of shots when I have time to illustrate the hit rate. Need to think of some sort of methodology to keep it semi-consistent.
Some examples of what you consider "missed" focus would be helpful along with some indication as to why you believe focus to be the issue.

QuoteOriginally posted by awscreo Quote
Mainly concerned with accuracy
Define accuracy. Remember that MFT (your point of comparison in the original post) provides significantly greater DOF for a given FOV and focus distance. Remember too that lack of precision can mask accuracy and that the PDAF detectors on your K-1 will detect an OOF condition at f/1.8 the same as at f/2.8. If exposure aperture is wider than f/2.8 the incidence of missed focus will be higher than if you were using the same setting in live view using CDAF.

FWIW, I don't use PDAF if fine focus and accuracy are the goals.

A few more things:
1. What is a "smc motor"? SMC is a coating technology (Super Multi Coating) dating back to about 1969.
2. In an AF system, the responsibility of attaining focus falls to the body AF system or the user. The lens does what it can to follow those orders.
3. DOF with a 50mm lens and f/2.8 on the K-1 for a subject at 2m is 2.7cm for acceptable focus at moderate enlargement (8x10" print) and "normal" viewing distance (~20"). That is fairly thin. A 25mm lens for MFT provides almost twice that.


Steve

Last edited by stevebrot; 10-01-2016 at 05:19 PM.
10-01-2016, 06:24 PM   #12
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QuoteOriginally posted by stevebrot Quote
Unless something has changed the DA 50/1.8 is not on the list of official FF compatible lenses, though some users are happy with its performance on the K-1. My experience on 35mm film is that the lens has significant vignette unless stopped down and is noticeably soft in the corners. Whether the corner softness is due to field curvature, I did not explore.

My conclusion was that I have better fast 50s in my bag for shooting 35mm film and if I had a K-1, the DA 50/1.8 would not be in the bag, but it would not be due to deficiencies in its AF performance.



Some examples of what you consider "missed" focus would be helpful along with some indication as to why you believe focus to be the issue.



Define accuracy. Remember that MFT (your point of comparison in the original post) provides significantly greater DOF for a given FOV and focus distance. Remember too that lack of precision can mask accuracy and that the PDAF detectors on your K-1 will detect an OOF condition at f/1.8 the same as at f/2.8. If exposure aperture is wider than f/2.8 the incidence of missed focus will be higher than if you were using the same setting in live view using CDAF.

FWIW, I don't use PDAF if fine focus and accuracy are the goals.

A few more things:
1. What is a "smc motor"? SMC is a coating technology (Super Multi Coating) dating back to about 1969.
2. In an AF system, the responsibility of attaining focus falls to the body AF system or the user. The lens does what it can to follow those orders.
3. DOF with a 50mm lens and f/2.8 on the K-1 for a subject at 2m is 2.7cm for acceptable focus at moderate enlargement (8x10" print) and "normal" viewing distance (~20"). That is fairly thin. A 25mm lens for MFT provides almost twice that.


Steve
1. My bad, I assumed that meant screw drive motor, wasn't paying attention.
2. If that's true, then I guess I'll never be able to get as many keepers as I had on mft
3. Dof of 25mm 1.4 lens on mft is the same as 50mm 2.8 on ff. EM1 was able to easily attain focus, whatever the reason was.

Accuracy - ability to aim the focus point on an eye of the subject (for example) and get good focus.
As for indications of missed focus - I aimed at a person's eye with single focus point, holding the camera steadily (with stabilization system on), in good light, and failed to attain good focus on the eye. Happened enough times to see some sort of a pattern.

50 1.8 is not FF rated, sure, but it only vignettes noticeably at 1.8, and when it does attain good focus is razor sharp f4 onwards (with 2.8 being quite sharp as well). I understand that there are better 50s, but this was a rush purchase for the upcoming trip, and I had no resources to purchase a higher grade lens at that moment. In any rate, i'm quite happy with it optically and do not feel the need to get another 50 for now, instead saving up for other lenses I want to buy.
10-01-2016, 07:53 PM   #13
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QuoteOriginally posted by awscreo Quote
Dof of 25mm 1.4 lens on mft is the same as 50mm 2.8 on ff.
That is true. To even the playing field, up-sample your MFT image to 36Mpx and see if you are still satisfied.

QuoteOriginally posted by awscreo Quote
Accuracy - ability to aim the focus point on an eye of the subject (for example) and get good focus.
Accuracy: whether the plane of focus and the subject plane are the same within the limits of detection
Precision: how frequently you can accomplish the above

Edit: The eye example is brought up frequently and when that happens, I tend to roll my eyes. There are mirrorless cameras that do subject evaluation and will do CDAF focus to the eye with amazing accuracy. Your K-1 will not do that. FWIW, neither will the Nikon D810. If given a non-ambiguous target within the bounds of the AF point, PDAF will nail your subject's eye. If the brow, cheek, or nose are within the scope of the AF point, any of those may fall to focus more strongly and you may be disappointed.

QuoteOriginally posted by awscreo Quote
50 1.8 is not FF rated, sure, but it only vignettes noticeably at 1.8, and when it does attain good focus is razor sharp f4 onwards (with 2.8 being quite sharp as well). I understand that there are better 50s...
Sorry for sending you down a rat hole. You were wondering if PDAF would be better with a different lens. For the currently available Pentax AF 50mm primes, I probably should have just said NO, unequivocally NO.* Sorry for going off on its quality and suitability for FF. It is a decent little lens and very fun to shoot with. FWIW, I have no complaints about AF results with my copy of the DA 50/1.8.


Steve


* The same is basically true even for legacy F 50/1.4, 50/1.7, and FA 50/1.7. At issue are the precision limitations of PDAF and those are the same across all brands.

Last edited by stevebrot; 10-01-2016 at 08:45 PM. Reason: Corrected terminology
10-01-2016, 08:17 PM   #14
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QuoteOriginally posted by stevebrot Quote
That is true. To even the playing field, up-sample your MFT image to 36Mpx and see if you are still satisfied.



Accuracy: whether the focus plane and the subject plane are the same within the limits of detection
Precision: how frequently you can accomplish the above

Edit: The eye example is brought up frequently and when that happens, I tend to roll my eyes. There are mirrorless cameras that do subject evaluation and will do CDAF focus to the eye with amazing accuracy. Your K-1 will not do that. FWIW, neither will the Nikon D810. If given a non-ambiguous target within the bounds of the focus point, PDAF will nail your subject's eye. If the brow, cheek, or nose are within the scope of the focus point, any of those may fall to focus more strongly and you may be disappointed.



Sorry for sending you down a rat hole. You were wondering if PDAF would be better with a different lens. For the currently available Pentax AF 50mm primes, I probably should have just said NO, unequivocally NO.* Sorry for going off on its quality and suitability for FF. It is a decent little lens and very fun to shoot with. FWIW, I have no complaints about AF results with my copy of the DA 50/1.8.


Steve


* The same is basically true even for legacy F 50/1.4, 50/1.7, and FA 50/1.7. At issue are the precision limitations of PDAF and those are the same across all brands.
EM1 actually has pdaf too, although I've never checked what it uses when focusing native mft lenses (such as 25 1.4).

Erm, I'm sure up scaling the image from 16mp to 36mp would soften the entire image, but it won't change the fact that camera has indeed nailed focus on the eye (or wherever I've focused on with the pointer). 16mp is plenty of resolution to see whether you've missed by even a bit at 100% zoom.
When I say that focus with 50 1.8 missed I mean you can see another area (in front or behind the target) in focus, meaning that camera had misjudged the correct distance to the focused area.

If what you're saying is true then I guess I'd have to live with that, and I missed that in my research before switching to a dslr system. Ive watched and read several reviews for other ff bodies, and never heard anyone mention that this kind of focusing system is inferior to mirrorless ones (if I'm understanding correctly), and usually people praising af systems in say d750 for being able to quickly aquire focus even in dim environments. I've used d800 few times at my old work place, and don't remember it missing focus that much, although I've only used it with pro lenses such as 24-70 and 105 micro.

Maybe with time I'll figure out how to get more successful shots. But if Pentax pro zooms don't improve focusing accuracy compared to a 100$ screw drive prime, maybe I should switch my priorities in acquiring gear.

---------- Post added 10-01-16 at 08:21 PM ----------

QuoteOriginally posted by stevebrot Quote
That is true. To even the playing field, up-sample your MFT image to 36Mpx and see if you are still satisfied.



Accuracy: whether the focus plane and the subject plane are the same within the limits of detection
Precision: how frequently you can accomplish the above

Edit: The eye example is brought up frequently and when that happens, I tend to roll my eyes. There are mirrorless cameras that do subject evaluation and will do CDAF focus to the eye with amazing accuracy. Your K-1 will not do that. FWIW, neither will the Nikon D810. If given a non-ambiguous target within the bounds of the focus point, PDAF will nail your subject's eye. If the brow, cheek, or nose are within the scope of the focus point, any of those may fall to focus more strongly and you may be disappointed.



Sorry for sending you down a rat hole. You were wondering if PDAF would be better with a different lens. For the currently available Pentax AF 50mm primes, I probably should have just said NO, unequivocally NO.* Sorry for going off on its quality and suitability for FF. It is a decent little lens and very fun to shoot with. FWIW, I have no complaints about AF results with my copy of the DA 50/1.8.


Steve


* The same is basically true even for legacy F 50/1.4, 50/1.7, and FA 50/1.7. At issue are the precision limitations of PDAF and those are the same across all brands.
Just to clarify, I'm mainly trying to figure all this stuff out for D fa zooms such as 24-70 2.8 or 70-200 2.8, not other 50mm primes.
10-01-2016, 11:17 PM   #15
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QuoteOriginally posted by awscreo Quote
Mainly concerned with accuracy
Thanks for the clarification. I own a K1 and I went through focus issues. Two practical things to consider with the K1:
- Area of PDAF points: K1 points are larger than K3 (AF module was borrowed from the K3, but to cover a larger frame without additional AF points). When focusing on a surface that is smaller than actual size of AF point, random error is introduced by the non overlapping portion of the AF point area and subject.
- AF systematic error require fine tuning (same as other DSLR).
In order to distinguish what is the problem you are having, use a good sized subject, if focus error disappear, then you've got to consider AF point area in your shooting, if focus error does not disappear, then you've got to go through a AF fine adjust.

---------- Post added 02-10-16 at 08:54 ----------

QuoteOriginally posted by awscreo Quote
but it won't change the fact that camera has indeed nailed focus on the eye
If you are doing portrait shot with 50mm f1.8 on FF ("focus on the eye"), then your camera is positioned at about 5 feet from your subject, in that case K1 is capable of focusing on the eye without error (except if your camera copy is out of spec). If you want to focus on the eye and have shallow DoF with the eye in focus, and you are 30 feet from the subject, in that case, the K1 AF point area is too large to focus on the eye, but anyway DoF is so large (even at f1.8) that whether you focus on the eye or on the head does not matter much.

To be honest, if your K1 is within tolerances, AF fine tuned, you should not have issues within realistic shooting distance (given focal length). Now , if you try to explore the limits of K1 AF capabilities by using uncommon focus conditions, you'll defeat it faster than with some other brands of cameras. I mean, as a photographer, the goal is not to use conditions to make the camera AF fail. The amount of sharp photos with tiny DoF that have already been posted by many K1 owners in various threads of Pentax forum (shot with 77 f1.8, 85 f1.4, 300 f2.8, 450 f5.6) bring some evidence that K1 AF works well including with f1.4 lenses.

Last edited by biz-engineer; 10-02-2016 at 12:02 AM.
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