FA 50/1.7 vs. 77 ltd autofocus speed...

jinskeep · 08-09-2015, 07:26 AM

Hello, I am somewhat new to Pentax, at least the digital world of Pentax. I have been using a K200D with legacy glass and started to believe that I needed auto focus for two reasons. 1) my favorite two subjects run around the house and are hard to catch with manual focus, 2) those lenses are a little difficult to focus accurately consistently. I recently purchased a 20-40 ltd ( about a year ago) and really like that lens for the most part, its pretty slow but very nice otherwise. The Autofocus seems pretty quick though I have had a few times where it hunts and wont focus at all, this isn't the norm.
So, in my hunt for a slightly longer lens to replace my 100/2.8 smc-m with, I have been considering a 77/1.8, 70/2.4, and at one time the 100/2.8 macro. I have pretty much settled on purchasing a 77/1.8. The 100/2.8 ended up off the list because its a macro and is a little slower in the auto focus speed department. However, a local store had one of those as well as an FA 50/1.7, so I looked at both. Both were REALLY slow and neither wanted to lock focus, except on stationary targets and even then the 100/2.8 needed a bit of assistance. The 50mm being the better of the two which I expected, but both lenses left me feeling like they weren't up to the task. I am seriously wondering if this is just an FA series lens thing or maybe these two lenses focus that slow...
MY real question is, how does the 77/1.8 compare with the 50/1.7 for auto focus speed? I know the 70/2.4 is supposed to faster, but not by much, than the 77. With what I was seeing yesterday, I am wondering if I am better off with manual focus glass, in which case it may be better to save up for the Ziess 85/1.4. I really hate to do that however.
Any suggestions/ input would be greatly appreciated.

stevebrot · 08-09-2015, 01:23 PM

Welcome to the Pentax Forums!

You will pay a premium price for the FA 50/1.7 beyond the actual value/performance of the lens. As for the FA 77/1.8, I own that lens and while the AF is not slow, it is not particularly quick either. For my money, I would get the DA 50/1.8 and even then I would not expect the AF to keep up with children or pets when mounted to the K200D. To be honest, I would not expect any currently available K-mount AF lens to be particularly fast focus on your camera.

Steve

**boriscleto** · 08-09-2015, 01:52 PM

Originally posted by stevebrot

You will pay a premium price for the FA 50/1.7 beyond the actual value/performance of the lens.

Unless you get lucky like I did and find it for $100 with a PZ-70 and Tamron 28-200.

At this point you might be better off investing in a camera with better AF, like the K-3.

virusn3t · 08-09-2015, 02:16 PM

Maybe is the camera fault, even my K30 haunts with dime light on interiors... I have the 77, a Smc-F 50 1.4, and the zeiss 85, the most fastest in good light is the 50, on bad light theyre even on AF speed, if something moves i cant focus anything at 1.4 on the zeiss

normhead · 08-09-2015, 02:21 PM

Originally posted by virusn3t

my K30 haunts with dime light on interiors..

Your K-30 is a ghost camera? Does it also go bump in the night?

You gotta love spell check.

virusn3t · 08-09-2015, 02:27 PM

Originally posted by normhead

Your K-30 is a ghost camera? Does it also go bump in the night?

You gotta love spell check.

Is even worse when your phone is in spanish (my Mother language), you are trying to write in english, and autocowreck to spanish or to some kind of spanglish

jinskeep · 08-09-2015, 02:54 PM

Awesome... Love the auto correct thing.
SO, the camera is really the big issue? That is a real problem.
Is the K-3 or even the K-5ii or k-50 really significantly better in this regard?

**boriscleto** · 08-09-2015, 03:07 PM

Originally posted by jinskeep

Awesome... Love the auto correct thing.
SO, the camera is really the big issue? That is a real problem.
Is the K-3 or even the K-5ii or k-50 really significantly better in this regard?

The AF in the K200D is SAFOX VIII, designed in 2003. The AF in the K-5 II or K-3 is SAFOX X, 2 generations newer. The K-5 II has 1 F/2.8 focus point, the K-3 has 3. The K-3 has predictive AF as well, it isn't as good as Canikon yet, but at least it has it.

virusn3t · 08-09-2015, 03:11 PM

Originally posted by jinskeep

Awesome... Love the auto correct thing.
SO, the camera is really the big issue? That is a real problem.
Is the K-3 or even the K-5ii or k-50 really significantly better in this regard?

It can be a big issue, from the 3 cameras you listed, the K3 have better AF motor and software, but i cant tell how much better is against the K200D.

waterfall · 08-09-2015, 04:40 PM

AF lock time on my FA 77, mounted on a K-3, is inversely proportional to the shutter speed. At 1/500 or >, focus lock on a moving target like my Grandson is instantaneous. At 1/100 or less, AF will search for a moving target and fail to lock. I use TAV mode in poor light or with fast moving subjects.

stevebrot · 08-09-2015, 06:32 PM

Originally posted by waterfall

AF lock time on my FA 77, mounted on a K-3, is inversely proportional to the shutter speed. At 1/500 or >, focus lock on a moving target like my Grandson is instantaneous. At 1/100 or less, AF will search for a moving target and fail to lock. I use TAV mode in poor light or with fast moving subjects.

Is it the shutter speed or the amount of light? I just did a quick trial with my FA 77 and if there is a difference with shutter speed, it is subtle...at least on my K-3.

Steve

waterfall · 08-10-2015, 05:02 AM

Originally posted by stevebrot

Is it the shutter speed or the amount of light? I just did a quick trial with my FA 77 and if there is a difference with shutter speed, it is subtle...at least on my K-3.

Steve

Definitely the light, if using Av setting. Bumping the ISO with Tav setting at higher shutter speeds makes the AF quick.

jk333 · 08-10-2015, 05:30 AM

Originally posted by virusn3t

It can be a big issue, from the 3 cameras you listed, the K3 have better AF motor and software, but i cant tell how much better is against the K200D.

The K50 autofocus is better than the K200 as well. A used K5 is probably the better purchase if you can really get it close to $300. Also, the DA lenses focus faster than the FA lenses.

K5 & DA70 is my recommendation. Possibly DA50 as recommended above depending on focal length.

Nicolas06 · 08-26-2015, 12:25 AM

Originally posted by boriscleto

The AF in the K200D is SAFOX VIII, designed in 2003. The AF in the K-5 II or K-3 is SAFOX X, 2 generations newer. The K-5 II has 1 F/2.8 focus point, the K-3 has 3. The K-3 has predictive AF as well, it isn't as good as Canikon yet, but at least it has it.

I would not say that K5-II and K-3 are same generation AF whatever the marketing might say.

K5-II as 11 points, K3 27
K3 has faster screw drive motor
K3 focus faster and more decisively.
K5-II off center AF point are huge, this is detrimental for precise focusisng (like focussing on the eye for a portrait). K3 has small off center AF points. For K3, the bigger point is center AF while for K5-II it was the smallest one. The size of the center AF point didn't change.
K5-II as 77 point B&W metering and K3 has 86K+ RGB metering. Allowing for tracking of subject by color and shape.

The only improvement that K5-II has vs K5 for AF (and in general) is that the AF work well in low light and has improved accurary for fast lenses. K3 keep this.

Also whatever the marketing say, K3 has no predictive AF to me but it has indeed tracking thanks to its far greater metering system. To me tracking is being to follow the subject while predicitive AF is being to guess in advence where the subject will be soon. This in particular allow to continue to move the AF while the mirror is up, preparing to take the photo.

Nicolas06 · 08-26-2015, 12:35 AM

To get the OP question if you really need good AF K5 is okish if you don't plan to focus in low light or don't plan for shallow deph of field (like a few center deph of field). This mean no apperture faster than f/2.8 or if you are quite close like and headshot, not faster than f/4 - f/5.6. The AF point are too big to be precise on shallow deph of field shoots. People that use quite large apperture and need precise focus tend to correct the focus manually to nail it perfectly.

K5-II bring low light support and K3 is the first Pentax body with great still AF support. For moving subjects, some sigma lenses are good with K3 or K3-II and the newest DFA lenses should be good too. No Pentax body has the performance of the best Canikon for sports/action shoots.

FA77 and DA50 lenses are not especially great for AF but if the subject isn't moving fast and the apperture isn't too large with K3 is should work just fine. I'd expect a sigma 24-70 f/2.8 to perform significantly faster through.

08-09-2015, 07:26 AM	#1
jinskeep New Member Join Date: Aug 2015 Posts: 8	FA 50/1.7 vs. 77 ltd autofocus speed... Hello, I am somewhat new to Pentax, at least the digital world of Pentax. I have been using a K200D with legacy glass and started to believe that I needed auto focus for two reasons. 1) my favorite two subjects run around the house and are hard to catch with manual focus, 2) those lenses are a little difficult to focus accurately consistently. I recently purchased a 20-40 ltd ( about a year ago) and really like that lens for the most part, its pretty slow but very nice otherwise. The Autofocus seems pretty quick though I have had a few times where it hunts and wont focus at all, this isn't the norm. So, in my hunt for a slightly longer lens to replace my 100/2.8 smc-m with, I have been considering a 77/1.8, 70/2.4, and at one time the 100/2.8 macro. I have pretty much settled on purchasing a 77/1.8. The 100/2.8 ended up off the list because its a macro and is a little slower in the auto focus speed department. However, a local store had one of those as well as an FA 50/1.7, so I looked at both. Both were REALLY slow and neither wanted to lock focus, except on stationary targets and even then the 100/2.8 needed a bit of assistance. The 50mm being the better of the two which I expected, but both lenses left me feeling like they weren't up to the task. I am seriously wondering if this is just an FA series lens thing or maybe these two lenses focus that slow... MY real question is, how does the 77/1.8 compare with the 50/1.7 for auto focus speed? I know the 70/2.4 is supposed to faster, but not by much, than the 77. With what I was seeing yesterday, I am wondering if I am better off with manual focus glass, in which case it may be better to save up for the Ziess 85/1.4. I really hate to do that however. Any suggestions/ input would be greatly appreciated.

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08-09-2015, 01:23 PM	#2
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Welcome to the Pentax Forums! You will pay a premium price for the FA 50/1.7 beyond the actual value/performance of the lens. As for the FA 77/1.8, I own that lens and while the AF is not slow, it is not particularly quick either. For my money, I would get the DA 50/1.8 and even then I would not expect the AF to keep up with children or pets when mounted to the K200D. To be honest, I would not expect any currently available K-mount AF lens to be particularly fast focus on your camera. Steve

08-09-2015, 01:52 PM	#3
boriscleto Loyal Site Supporter Join Date: Dec 2009 Location: North Syracuse, NY Photos: Gallery Posts: 16,475	Originally posted by stevebrot You will pay a premium price for the FA 50/1.7 beyond the actual value/performance of the lens. Unless you get lucky like I did and find it for $100 with a PZ-70 and Tamron 28-200. At this point you might be better off investing in a camera with better AF, like the K-3.

08-09-2015, 02:16 PM	#4
virusn3t Veteran Member Join Date: Jul 2014 Posts: 676	Maybe is the camera fault, even my K30 haunts with dime light on interiors... I have the 77, a Smc-F 50 1.4, and the zeiss 85, the most fastest in good light is the 50, on bad light theyre even on AF speed, if something moves i cant focus anything at 1.4 on the zeiss

08-09-2015, 02:21 PM	#5
normhead Pentaxian Join Date: Jun 2007 Location: Near Algonquin Park Photos: Gallery \| Albums Posts: 40,451	Originally posted by virusn3t my K30 haunts with dime light on interiors.. Your K-30 is a ghost camera? Does it also go bump in the night? You gotta love spell check.

08-09-2015, 02:27 PM	#6
virusn3t Veteran Member Join Date: Jul 2014 Posts: 676	Originally posted by normhead Your K-30 is a ghost camera? Does it also go bump in the night? You gotta love spell check. Is even worse when your phone is in spanish (my Mother language), you are trying to write in english, and autocowreck to spanish or to some kind of spanglish

08-09-2015, 02:54 PM	#7
jinskeep New Member Join Date: Aug 2015 Posts: 8 Original Poster	Awesome... Love the auto correct thing. SO, the camera is really the big issue? That is a real problem. Is the K-3 or even the K-5ii or k-50 really significantly better in this regard?

08-09-2015, 03:07 PM	#8
boriscleto Loyal Site Supporter Join Date: Dec 2009 Location: North Syracuse, NY Photos: Gallery Posts: 16,475	Originally posted by jinskeep Awesome... Love the auto correct thing. SO, the camera is really the big issue? That is a real problem. Is the K-3 or even the K-5ii or k-50 really significantly better in this regard? The AF in the K200D is SAFOX VIII, designed in 2003. The AF in the K-5 II or K-3 is SAFOX X, 2 generations newer. The K-5 II has 1 F/2.8 focus point, the K-3 has 3. The K-3 has predictive AF as well, it isn't as good as Canikon yet, but at least it has it.

08-09-2015, 03:11 PM	#9
virusn3t Veteran Member Join Date: Jul 2014 Posts: 676	Originally posted by jinskeep Awesome... Love the auto correct thing. SO, the camera is really the big issue? That is a real problem. Is the K-3 or even the K-5ii or k-50 really significantly better in this regard? It can be a big issue, from the 3 cameras you listed, the K3 have better AF motor and software, but i cant tell how much better is against the K200D.

08-09-2015, 04:40 PM	#10
waterfall Veteran Member Join Date: Apr 2013 Location: Northern Minnesota Photos: Gallery \| Albums Posts: 1,812	AF lock time on my FA 77, mounted on a K-3, is inversely proportional to the shutter speed. At 1/500 or >, focus lock on a moving target like my Grandson is instantaneous. At 1/100 or less, AF will search for a moving target and fail to lock. I use TAV mode in poor light or with fast moving subjects.

08-09-2015, 06:32 PM	#11
stevebrot Otis Memorial Pentaxian Join Date: Mar 2007 Location: Vancouver (USA) Photos: Gallery \| Albums Posts: 42,007	Originally posted by waterfall AF lock time on my FA 77, mounted on a K-3, is inversely proportional to the shutter speed. At 1/500 or >, focus lock on a moving target like my Grandson is instantaneous. At 1/100 or less, AF will search for a moving target and fail to lock. I use TAV mode in poor light or with fast moving subjects. Is it the shutter speed or the amount of light? I just did a quick trial with my FA 77 and if there is a difference with shutter speed, it is subtle...at least on my K-3. Steve

08-10-2015, 05:02 AM	#12
waterfall Veteran Member Join Date: Apr 2013 Location: Northern Minnesota Photos: Gallery \| Albums Posts: 1,812	Originally posted by stevebrot Is it the shutter speed or the amount of light? I just did a quick trial with my FA 77 and if there is a difference with shutter speed, it is subtle...at least on my K-3. Steve Definitely the light, if using Av setting. Bumping the ISO with Tav setting at higher shutter speeds makes the AF quick.

08-10-2015, 05:30 AM	#13
jk333 Senior Member Join Date: Oct 2008 Location: bev Posts: 181	Originally posted by virusn3t It can be a big issue, from the 3 cameras you listed, the K3 have better AF motor and software, but i cant tell how much better is against the K200D. The K50 autofocus is better than the K200 as well. A used K5 is probably the better purchase if you can really get it close to $300. Also, the DA lenses focus faster than the FA lenses. K5 & DA70 is my recommendation. Possibly DA50 as recommended above depending on focal length.

08-26-2015, 12:25 AM	#14
Nicolas06 Veteran Member Join Date: Nov 2013 Posts: 4,854	Originally posted by boriscleto The AF in the K200D is SAFOX VIII, designed in 2003. The AF in the K-5 II or K-3 is SAFOX X, 2 generations newer. The K-5 II has 1 F/2.8 focus point, the K-3 has 3. The K-3 has predictive AF as well, it isn't as good as Canikon yet, but at least it has it. I would not say that K5-II and K-3 are same generation AF whatever the marketing might say. K5-II as 11 points, K3 27 K3 has faster screw drive motor K3 focus faster and more decisively. K5-II off center AF point are huge, this is detrimental for precise focusisng (like focussing on the eye for a portrait). K3 has small off center AF points. For K3, the bigger point is center AF while for K5-II it was the smallest one. The size of the center AF point didn't change. K5-II as 77 point B&W metering and K3 has 86K+ RGB metering. Allowing for tracking of subject by color and shape. The only improvement that K5-II has vs K5 for AF (and in general) is that the AF work well in low light and has improved accurary for fast lenses. K3 keep this. Also whatever the marketing say, K3 has no predictive AF to me but it has indeed tracking thanks to its far greater metering system. To me tracking is being to follow the subject while predicitive AF is being to guess in advence where the subject will be soon. This in particular allow to continue to move the AF while the mirror is up, preparing to take the photo.

08-26-2015, 12:35 AM	#15
Nicolas06 Veteran Member Join Date: Nov 2013 Posts: 4,854	To get the OP question if you really need good AF K5 is okish if you don't plan to focus in low light or don't plan for shallow deph of field (like a few center deph of field). This mean no apperture faster than f/2.8 or if you are quite close like and headshot, not faster than f/4 - f/5.6. The AF point are too big to be precise on shallow deph of field shoots. People that use quite large apperture and need precise focus tend to correct the focus manually to nail it perfectly. K5-II bring low light support and K3 is the first Pentax body with great still AF support. For moving subjects, some sigma lenses are good with K3 or K3-II and the newest DFA lenses should be good too. No Pentax body has the performance of the best Canikon for sports/action shoots. FA77 and DA50 lenses are not especially great for AF but if the subject isn't moving fast and the apperture isn't too large with K3 is should work just fine. I'd expect a sigma 24-70 f/2.8 to perform significantly faster through.