K70 and Sigma 18-35 1.8 ART

AntonioS · 03-14-2023, 08:54 AM

Hello,

I'm planning to buy an used K70 but I had a bad time with the Sigma 18-35 F1.8 ART when used with the K3-II. The AF missed to properly fosus about 50% of the times. Strangely, this lens always worked perfectly with the K5-II.

Does anyone have experienced AF issues with the K70 and the Sigma 18-35 F1.8 ART together ?

Cheers,

Antonio

AfterPentax Mark II · 03-14-2023, 09:07 AM

The problem is not the camera, but the lens. Chances are it does not perform well on your K-70. It is widely documented that with all mounts AF is terrible. I just bought one , tried it on my K-3 II and KP and although most went well, I returned it because the problem was each time between one photo and the next, no steady performance. The K-70 has some similarities with the KP (yes, I know they are both camera's

) in its innards. So I am afraid, you are in for a troubled journey with that K-70 / 18-35 combo. I was not able to detect a system in its failures and felt obliged to look for a better performing lens.

AntonioS · 03-14-2023, 10:03 AM

Originally posted by AfterPentax Mark II

The problem is not the camera, but the lens. Chances are it does not perform well on your K-70. It is widely documented that with all mounts AF is terrible. I just bought one , tried it on my K-3 II and KP and although most went well, I returned it because the problem was each time between one photo and the next, no steady performance. The K-70 has some similarities with the KP (yes, I know they are both camera's

) in its innards. So I am afraid, you are in for a troubled journey with that K-70 / 18-35 combo. I was not able to detect a system in its failures and felt obliged to look for a better performing lens.

So, basically bad news... I just read about the solenoid problem. Maybe it would be better to avoid it.

The K70 has the Safox X AF system, the same of the K5 II.. It should work...

Thanks !

**pres589** · 03-14-2023, 10:19 AM

Sigma glass is "fun" in that sometimes it is that specific copy of the lens that doesn't perform well with regard to autofocus. Also sometimes it's the body and how it works with that copy of the lens. The best thing, which is often difficult, would be to try the copy of the lens you want to buy on the copy of the body you own.

I love some Sigma lenses but they do make it difficult sometimes... It does seem like they've done a better job about this in recent years, especially in mirrorless mounts.

leekil · 03-14-2023, 10:36 AM

Originally posted by AntonioS

The K70 has the Safox X AF system, the same of the K5 II.. It should work...

I believe the AF issues he is referring to are on the Sigma side, not the Pentax one.

gatorguy · 03-14-2023, 10:48 AM

Originally posted by AntonioS

So, basically bad news... I just read about the solenoid problem. Maybe it would be better to avoid it.

The K70 has the Safox X AF system, the same of the K5 II.. It should work...

Thanks !

I would not worry about a K-70 and aperture failure for even a moment. All existing evidence points to it being a rarity, no more prevalent than other causes of failure across camera brands.

As for the Sigma lens it may come down to what your intended use is. If it's for low-light interiors, not much action/movement, I think you would be fine. Sometimes it just needs another tap on the focus to lock it in. I have the lens (and the camera) and like it. I've used it under a variety of scenarios from architecture to stage events. You just have to be willing to accept a slightly lower hit count for those fast-moving musicians 'cause there's probably going to be some misfocused. Not like most or even many, but more than you might be accustomed to. Or not. Much depends on how good you are with the camera.

AntonioS · 03-14-2023, 10:59 AM

Originally posted by gatorguy

I would not worry about a K-70 and aperture failure for even a moment. All existing evidence points to it being a rarity, no more prevalent than other causes of failure across camera brands.

As for the Sigma lens it may come down to what your intended use is. If it's for low-light interiors, not much action/movement, I think you would be fine. Sometimes it just needs another tap on the focus to lock it in. I have the lens (and the camera) and like it. I've used it under a variety of scenarios from architecture to stage events. You just have to be willing to accept a slightly lower hit count for those fast-moving musicians 'cause there's probably going to be some misfocused. Not like most or even many, but more than you might be accustomed to. Or not. Much depends on how good you are with the camera.

Hi Gatorguy,

I've been using the K5-II with the 18-35 without any issues and the AF is working perfectly for my kind of use. But on the K3-II it misses a lot and enough to ruin the image, no matter if the subject is still, moving, under good light, etc... It's random.

I'll see with the seller if it would be possible to return the camera in case of problems. There are no Pentax dealers or service in my country.

Grimmus · 03-14-2023, 11:23 AM

What @gatorguy said! And if you are interested in nightscapes, the sigma 18-35 is about as good as it gets - great combo with flippy screen K-70. I don't find my sigma significantly different to other pentax lenses (on a Kp or K-3)

colten.photo · 03-14-2023, 12:17 PM

I never had issues with mine. The AF was slow but usually accurate and the combo did take beautiful pictures.

I would not recommend it for moving subjects.

**UncleVanya** · 03-14-2023, 03:46 PM

Talk to @Digitalis about this lens. It has a reputation even on other brands for unreliable focus.

PardonMyShutterSound · 03-14-2023, 04:56 PM

I have used my Sigma on K-70 and on K1-I (in FF mode from 28-35mm with small cropping in post). I didn't have any problem with AF in both cases.
There is a lot of stories about problem with AF with this lens at Pentax bodies, my personal experience do not confirm those stories.
What I have to highlight that when I start to use lens with K1 at beginning I had problems with AF, but it was my wrong setup of camera. As soon as I understood it, I had no problems.

**tonyzoc** · 03-14-2023, 05:34 PM

I'm wondering if those with focus issues tried micro adjustments to the focus? I was having problem with the Tamron 10-24 only on my K10D. After adjusting micro focus settings I got it working better.

**UncleVanya** · 03-14-2023, 05:39 PM

Originally posted by tonyzoc

I'm wondering if those with focus issues tried micro adjustments to the focus? I was having problem with the Tamron 10-24 only on my K10D. After adjusting micro focus settings I got it working better.

Not as I understand it. Zooms tend to be more of an issue as they don’t always have the same adjustment required at different focal lengths. But in this case it was just inconsistent. I think Digitalis can detail it more effectively. I believe he tried multiple copies.

**tabz** · 03-15-2023, 01:10 AM

Originally posted by UncleVanya

Not as I understand it. Zooms tend to be more of an issue as they don’t always have the same adjustment required at different focal lengths. But in this case it was just inconsistent. I think Digitalis can detail it more effectively. I believe he tried multiple copies.

There are a USB docker for sigma lenses to tune AF four section of zoom range and four section of subject distance.

USB DOCK UD-01 | USB DOCK | Accessories | SIGMA Corporation

syyrmb · 03-15-2023, 02:54 AM

I used to have the K70 + Sigma 18-35 combo. When I first received the lens I found the focus through viewfinder very inconsistent, it's basically 50/50 hit and miss, so I put the lens to collect dust for a few weeks. Then one day I decided to try the lens again and the AF surprisingly works pretty well this time, and I used it more often, though not long enough the lens went back to its former state so I sold it. If you can tolerate holding the 800g lens and use live-view focus, then this lens doesn't have any AF issue as long as you don't need to track subjects. Holding the combo at night can be a physical exercise since LV focus is pretty slow when it gets dim.

03-14-2023, 08:54 AM	#1
AntonioS Senior Member Join Date: Dec 2018 Location: Rio de Janeiro Photos: Albums Posts: 113	K70 and Sigma 18-35 1.8 ART Hello, I'm planning to buy an used K70 but I had a bad time with the Sigma 18-35 F1.8 ART when used with the K3-II. The AF missed to properly fosus about 50% of the times. Strangely, this lens always worked perfectly with the K5-II. Does anyone have experienced AF issues with the K70 and the Sigma 18-35 F1.8 ART together ? Cheers, Antonio

03-14-2023, 10:03 AM	#3
AntonioS Senior Member Join Date: Dec 2018 Location: Rio de Janeiro Photos: Albums Posts: 113 Original Poster	Originally posted by AfterPentax Mark II The problem is not the camera, but the lens. Chances are it does not perform well on your K-70. It is widely documented that with all mounts AF is terrible. I just bought one , tried it on my K-3 II and KP and although most went well, I returned it because the problem was each time between one photo and the next, no steady performance. The K-70 has some similarities with the KP (yes, I know they are both camera's ) in its innards. So I am afraid, you are in for a troubled journey with that K-70 / 18-35 combo. I was not able to detect a system in its failures and felt obliged to look for a better performing lens. So, basically bad news... I just read about the solenoid problem. Maybe it would be better to avoid it. The K70 has the Safox X AF system, the same of the K5 II.. It should work... Thanks ! Last edited by AntonioS; 03-14-2023 at 10:21 AM.

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03-14-2023, 09:07 AM	#2
AfterPentax Mark II Pentaxian Join Date: Mar 2021 Posts: 1,467	The problem is not the camera, but the lens. Chances are it does not perform well on your K-70. It is widely documented that with all mounts AF is terrible. I just bought one , tried it on my K-3 II and KP and although most went well, I returned it because the problem was each time between one photo and the next, no steady performance. The K-70 has some similarities with the KP (yes, I know they are both camera's ) in its innards. So I am afraid, you are in for a troubled journey with that K-70 / 18-35 combo. I was not able to detect a system in its failures and felt obliged to look for a better performing lens.

03-14-2023, 10:19 AM	#4
pres589 Site Supporter Join Date: Jan 2014 Location: Wichita, KS Photos: Albums Posts: 4,533	Sigma glass is "fun" in that sometimes it is that specific copy of the lens that doesn't perform well with regard to autofocus. Also sometimes it's the body and how it works with that copy of the lens. The best thing, which is often difficult, would be to try the copy of the lens you want to buy on the copy of the body you own. I love some Sigma lenses but they do make it difficult sometimes... It does seem like they've done a better job about this in recent years, especially in mirrorless mounts.

03-14-2023, 10:36 AM	#5
leekil Pentaxian Join Date: May 2016 Photos: Albums Posts: 2,003	Originally posted by AntonioS The K70 has the Safox X AF system, the same of the K5 II.. It should work... I believe the AF issues he is referring to are on the Sigma side, not the Pentax one.

03-14-2023, 10:48 AM	#6
gatorguy Moderator Join Date: Feb 2015 Location: Central Florida Photos: Gallery Posts: 6,094	Originally posted by AntonioS So, basically bad news... I just read about the solenoid problem. Maybe it would be better to avoid it. The K70 has the Safox X AF system, the same of the K5 II.. It should work... Thanks ! I would not worry about a K-70 and aperture failure for even a moment. All existing evidence points to it being a rarity, no more prevalent than other causes of failure across camera brands. As for the Sigma lens it may come down to what your intended use is. If it's for low-light interiors, not much action/movement, I think you would be fine. Sometimes it just needs another tap on the focus to lock it in. I have the lens (and the camera) and like it. I've used it under a variety of scenarios from architecture to stage events. You just have to be willing to accept a slightly lower hit count for those fast-moving musicians 'cause there's probably going to be some misfocused. Not like most or even many, but more than you might be accustomed to. Or not. Much depends on how good you are with the camera.

03-14-2023, 10:59 AM	#7
AntonioS Senior Member Join Date: Dec 2018 Location: Rio de Janeiro Photos: Albums Posts: 113 Original Poster	Originally posted by gatorguy I would not worry about a K-70 and aperture failure for even a moment. All existing evidence points to it being a rarity, no more prevalent than other causes of failure across camera brands. As for the Sigma lens it may come down to what your intended use is. If it's for low-light interiors, not much action/movement, I think you would be fine. Sometimes it just needs another tap on the focus to lock it in. I have the lens (and the camera) and like it. I've used it under a variety of scenarios from architecture to stage events. You just have to be willing to accept a slightly lower hit count for those fast-moving musicians 'cause there's probably going to be some misfocused. Not like most or even many, but more than you might be accustomed to. Or not. Much depends on how good you are with the camera. Hi Gatorguy, I've been using the K5-II with the 18-35 without any issues and the AF is working perfectly for my kind of use. But on the K3-II it misses a lot and enough to ruin the image, no matter if the subject is still, moving, under good light, etc... It's random. I'll see with the seller if it would be possible to return the camera in case of problems. There are no Pentax dealers or service in my country.

03-14-2023, 11:23 AM	#8
Grimmus Pentaxian Join Date: Jun 2010 Location: Newcastle (Aust.) Photos: Gallery \| Albums Posts: 348	What @gatorguy said! And if you are interested in nightscapes, the sigma 18-35 is about as good as it gets - great combo with flippy screen K-70. I don't find my sigma significantly different to other pentax lenses (on a Kp or K-3)

03-14-2023, 12:17 PM	#9
colten.photo Junior Member Join Date: Jan 2023 Posts: 34	I never had issues with mine. The AF was slow but usually accurate and the combo did take beautiful pictures. I would not recommend it for moving subjects.

03-14-2023, 03:46 PM	#10
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,460	Talk to @Digitalis about this lens. It has a reputation even on other brands for unreliable focus.

03-14-2023, 04:56 PM	#11
PardonMyShutterSound New Member Join Date: Nov 2022 Location: Ceske Budejovice Photos: Gallery \| Albums Posts: 24	I have used my Sigma on K-70 and on K1-I (in FF mode from 28-35mm with small cropping in post). I didn't have any problem with AF in both cases. There is a lot of stories about problem with AF with this lens at Pentax bodies, my personal experience do not confirm those stories. What I have to highlight that when I start to use lens with K1 at beginning I had problems with AF, but it was my wrong setup of camera. As soon as I understood it, I had no problems.

03-14-2023, 05:34 PM	#12
tonyzoc Loyal Site Supporter Join Date: Jul 2018 Posts: 992	I'm wondering if those with focus issues tried micro adjustments to the focus? I was having problem with the Tamron 10-24 only on my K10D. After adjusting micro focus settings I got it working better.

03-14-2023, 05:39 PM	#13
UncleVanya Loyal Site Supporter Join Date: Jul 2014 Photos: Gallery \| Albums Posts: 28,460	Originally posted by tonyzoc I'm wondering if those with focus issues tried micro adjustments to the focus? I was having problem with the Tamron 10-24 only on my K10D. After adjusting micro focus settings I got it working better. Not as I understand it. Zooms tend to be more of an issue as they don’t always have the same adjustment required at different focal lengths. But in this case it was just inconsistent. I think Digitalis can detail it more effectively. I believe he tried multiple copies.

03-15-2023, 01:10 AM	#14
tabz Site Supporter Join Date: Sep 2009 Photos: Albums Posts: 42	Originally posted by UncleVanya Not as I understand it. Zooms tend to be more of an issue as they don’t always have the same adjustment required at different focal lengths. But in this case it was just inconsistent. I think Digitalis can detail it more effectively. I believe he tried multiple copies. There are a USB docker for sigma lenses to tune AF four section of zoom range and four section of subject distance. USB DOCK UD-01 \| USB DOCK \| Accessories \| SIGMA Corporation

03-15-2023, 02:54 AM	#15
syyrmb Forum Member Join Date: Sep 2020 Location: Qingdao Posts: 94	I used to have the K70 + Sigma 18-35 combo. When I first received the lens I found the focus through viewfinder very inconsistent, it's basically 50/50 hit and miss, so I put the lens to collect dust for a few weeks. Then one day I decided to try the lens again and the AF surprisingly works pretty well this time, and I used it more often, though not long enough the lens went back to its former state so I sold it. If you can tolerate holding the 800g lens and use live-view focus, then this lens doesn't have any AF issue as long as you don't need to track subjects. Holding the combo at night can be a physical exercise since LV focus is pretty slow when it gets dim.