Discuss - Sigma 56mm f1.4 DC DN

speedy

Mu-43 Hall of Famer
Joined
Nov 27, 2015
Messages
2,071
I tried it again just now (with just indoor lighting) and weirdly enough I did not get any "false positive" confirmation or misfocus.
I don’t know if this applies to CDAF AF, but I’ve read quite a bit of research on how different temperature or wavelength light can affect PDAF. There seem to be a few Canon models that were affected by this. By what degree, and how often, I really can’t remember. Maybe something to keep in mind, & perhaps do a little test or 2, if it continues its random appearances
 

NIlaga

Mu-43 Regular
Joined
Feb 27, 2019
Messages
61
Location
Canada
Does Olympus simply find it more difficult with very fast aperture telephoto primes for some reason?
Missed focus with E-M1 mkII and 45mm Pro?
Interesting. I just tried a test this morning using books with contrasty titles and got 2 out of 10 that had focus confirmation but were actually out of focus.

He said he encounters back focus or front focus issues from his em1mkii and 45 1.2. I get totally out of focus images from the my em10mkii and 56 1.4.

Am I expecting too much in that there should be no focus confirmation at all if the subject is not in focus? :hmmm:
 

Baenwort

Mu-43 Regular
Joined
Aug 22, 2017
Messages
125
Location
Wisconsin, USA
Remember how computers work. The camera can't know what focus should look like so what it is doing is sampling the values of the pixels in the focus box and measuring when it has maximum contrast (difference between parts of the focus box) that reaches a mathematical maximum between each side of the focus movement.

Now in reality it is a lot more complex than that but it should help understand that due to the way the math works, with small focus boxes and lenses with high microcontrast, looking at high contrast subjects it might think it has found a suffiently contrasting focus position but be wrong.

This is purely a camera issue.
 

x_holger

Mu-43 Regular
Joined
Aug 14, 2012
Messages
94
Location
Berlin, Germany
Given the way CDAF works this doesn't make a lot of sense. The camera body just stops driving the lens if it considers the local maximum of contrast has been reached, by the body's own measurements. The lens has no idea what's going on.

If the body is asserting focus is reached when it isn't, then it's probably the body's fault. I had this happen a number of times with the 45mm f/1.8 on my old E-M5. I have also experienced it with the 8-18mm on my E-M1. The four Panasonic bodies that I've had (latest is GX850) never have a problem, and in fact focus all my lenses (including Olympus lenses) noticeably better than my E-M1. Based on that experience with two Olympus bodies and four Panasonic with numerous lenses from all manufacturers, it's two strikes against Olympus bodies and none against Panasonic bodies for S-AF.

That said, I suppose there could be a defect where the lens stops driving during AF, and so the body thinks it's reached the maximum attainable contrast simply because the lens won't adjust further.
Your point of view is too simplistic.
1. The E-M1 series has a hybrid AF system, a combination of CDAF and PDAF. The fine-tuning of this hybrid AF is not perfect and could be improved. Sometimes there are surprising errors /failures, hardly predictable.
2. CDAF has many limitations and needs a lot of innovative software to be improved in reliability. Panasonic developed DFD for that reason and Olympus was slow to introduce AI improved CDAF, just started that with the E-M1X really.
3. CDAF on Olympus cameras is reacting as to be expected for such a limited approach. It's not faulty in itself, just has many limitations that most people are aware of who use mFT since 2009. All early CDAF only mFT cameras had these limitations and DFD only works well in the newest top of the line cameras of Panasonic, newer than the GX8... like the G9.
 

wjiang

Mu-43 Legend
Joined
Sep 7, 2013
Messages
7,175
Location
Christchurch, New Zealand
Your point of view is too simplistic.
1. The E-M1 series has a hybrid AF system, a combination of CDAF and PDAF. The fine-tuning of this hybrid AF is not perfect and could be improved. Sometimes there are surprising errors /failures, hardly predictable.
2. CDAF has many limitations and needs a lot of innovative software to be improved in reliability. Panasonic developed DFD for that reason and Olympus was slow to introduce AI improved CDAF, just started that with the E-M1X really.
3. CDAF on Olympus cameras is reacting as to be expected for such a limited approach. It's not faulty in itself, just has many limitations that most people are aware of who use mFT since 2009. All early CDAF only mFT cameras had these limitations and DFD only works well in the newest top of the line cameras of Panasonic, newer than the GX8... like the G9.
What I described is CDAF by itself. Sure there are enhancements to it, but all such techniques are done by the body. My argument still stands that CDAF by itself is very simple, and when it gets wrong, it's usually the body (and whatever it tries to do to improve CDAF) at fault.

As you say, I've simply gotten used to it and make sure to always focus on high contrast.
 

NIlaga

Mu-43 Regular
Joined
Feb 27, 2019
Messages
61
Location
Canada
Went to the store to return the lens. Tried it on an EM10iii and the issue is also present on that body. It appears to be focus drive issue as per the camera store staff.
 

x_holger

Mu-43 Regular
Joined
Aug 14, 2012
Messages
94
Location
Berlin, Germany
Went to the store to return the lens. Tried it on an EM10iii and the issue is also present on that body. It appears to be focus drive issue as per the camera store staff.
Good to know. I had the same impression with my sample of the 1.4/56mm, some kind of focus drive issue of the lens.
 

speedy

Mu-43 Hall of Famer
Joined
Nov 27, 2015
Messages
2,071
Good to know. I had the same impression with my sample of the 1.4/56mm, some kind of focus drive issue of the lens.
Must be an Olympus issue. I've yet to give it a spin on my GX8, but I'm not anticipating any weirdness as it's pretty much the same AF system as my G9, with which I'm not seeing any issues at all.

People were talking about CA earlier in the thread, I think it's extremely well controlled. Wide open, or there abouts, it's far better than my Panasonic 42.5 f/1.7 -even after running the raw's through software. The Lumix 42.5 has a more smeared appearance to the CA, which is much more difficult to remove, whereas the Siggy has only the tiniest, narrow halo of blue/green in spots, which is very very simple to remove with a click, in SilkyPix. One such example around the roof line, in an extremely high contrast area, slightly behind the focal plane.
Subscribe to see EXIF info for this image (if available)

Nothing at all showed up in any of the other test shots, similar to this.

Subscribe to see EXIF info for this image (if available)


I think the Bokeh is very nice & smooth looking.
 

mnhoj

There and back again and again
Joined
Dec 3, 2011
Messages
1,602
Location
Los Angeles
Real Name
John M
Went to the store to return the lens. Tried it on an EM10iii and the issue is also present on that body. It appears to be focus drive issue as per the camera store staff.
Did you get to try a different lens?
So is their conclusion that the lens is incompatible with Olympus bodies?

Edit: Or did you get to try the lens in question on a Panny body?
 
Last edited:

NIlaga

Mu-43 Regular
Joined
Feb 27, 2019
Messages
61
Location
Canada
Did you get to try a different lens?
So is their conclusion that the lens is incompatible with Olympus bodies?
The store ordered another copy from their warehouse with ETA of around April 1st so I was not able to try another copy yet.

I contacted Sigma Canada's support and received the following response (Gentec is Canada's Sigma distributor):

"Hello Mr. NIlaga,

We haven’t seen this before or had any bulletins from Sigma about the lens. Usually mirrorless cameras have very accurate hybrid focusing using the main sensor. If the result was the same on another body then a second copy of the lens should operate correctly."

So no mention of incompatibility with Olympus.

Now after I returned the lens yesterday I've actually decided to skip the 56 and look for a 75. But with the support's reply, I'm willing to try another copy. I really like the output of the 56 1.4 from the few photos I took when I had the lens.

Edit: and from the photos shared by other members in the Showcase thread as well as on this post.
 
Last edited:

mnhoj

There and back again and again
Joined
Dec 3, 2011
Messages
1,602
Location
Los Angeles
Real Name
John M
The store ordered another copy and will arive sometime around April 1st so I was not able to try another copy yet. No mention of incompatibility with Olympus but the staff yesterday mentioned his experience using Sigma on his Nikon which is "hit or miss".

I contacted Sigma Canada's support and received the following response (Gentec is Canada's Sigma distributor):

"Hello Mr. NIlaga,

We haven’t seen this before or had any bulletins from Sigma about the lens. Usually mirrorless cameras have very accurate hybrid focusing using the main sensor. If the result was the same on another body then a second copy of the lens should operate correctly."

Now after I returned the lens yesterday I've actually decided to skip the 56 and look for a 75. But with the support's reply, I'm willing to try another copy. I really like the output of the 56 1.4 from the few photos I took when I had the lens.
Darn sorry to hear it.
After reading about your issues I decided to run my EM1.1 though a little testing. Staggered boxes with ingredients and chasing my cat around the house. It functions very well. My Em10ii(just sold it) seemed to be fine too.
I think that you and x_holger may have had bad copies which is two too many but hopefully you will have success with your next or with the excellent 75.
 

mnhoj

There and back again and again
Joined
Dec 3, 2011
Messages
1,602
Location
Los Angeles
Real Name
John M
Must be an Olympus issue. I've yet to give it a spin on my GX8, but I'm not anticipating any weirdness as it's pretty much the same AF system as my G9, with which I'm not seeing any issues at all.

People were talking about CA earlier in the thread, I think it's extremely well controlled. Wide open, or there abouts, it's far better than my Panasonic 42.5 f/1.7 -even after running the raw's through software. The Lumix 42.5 has a more smeared appearance to the CA, which is much more difficult to remove, whereas the Siggy has only the tiniest, narrow halo of blue/green in spots, which is very very simple to remove with a click, in SilkyPix. One such example around the roof line, in an extremely high contrast area, slightly behind the focal plane.View attachment 729617
Nothing at all showed up in any of the other test shots, similar to this.

View attachment 729618

I think the Bokeh is very nice & smooth looking.
I have similar findings as well concerning CA and the bokeh.
Hey wait. Aren't you supposed to be resting?!
 

speedy

Mu-43 Hall of Famer
Joined
Nov 27, 2015
Messages
2,071
I have similar findings as well concerning CA and the bokeh.
Hey wait. Aren't you supposed to be resting?!
He he he. Busted. Yep, I just think of it as part of my physio. Hung a small bag around my neck, popped the camera in, hobbled out the front door on the crutches, in my pyjamas, out onto the front lawn, and snapped a few shots. What a sight for sore eyes. One handed, balancing on my crutches. Thanks to the G9's lovely grip. Curiosity got the better of me :)
Obviously, I fared better than the cat :)
 

Reflector

Mu-43 Hall of Famer
Joined
Aug 31, 2013
Messages
2,107
For you guys with a fetish for Sigma lens. :biggrin:

Own three ones here myself unless you count the ghost designed (and produced?) lenses like the Olympus 25mm f/1.8 and Olympus 75mm f/1.8. I'd be happy to own more of them, Sigma ones or the ones that they made for Olympus with Olympus coatings and Olympus tech like the voice coil motor for the AF...

Must resist the urge to buy the 56mm at new prices even if I have the 45mm and 75mm...
 

speedy

Mu-43 Hall of Famer
Joined
Nov 27, 2015
Messages
2,071
Actually, I just managed to reproduce the false focus confirmation on my G9, but I had to deliberately try and do it. Smallest single point focus box, on a no contrast subject. It will very occasionally give a false green box focus confirmation/beep. But you have to try to force the issue. It won't do it with the pinpoint AF crosshair, or the larger sized focus boxes. I'd call that operator error personally.
 

Latest posts

Links on this page may be to our affiliates. Sales through affiliate links may benefit this site.
Mu-43 is a fan site and not associated with Olympus, Panasonic, or other manufacturers mentioned on this site.
Forum post reactions by Twemoji: https://github.com/twitter/twemoji
Copyright © 2009-2019 Amin Forums, LLC
Top Bottom