Batis 25mm Oled DOF display

[Massimo]

So I just bit the bullet and ordered one of the first Batis 25mm to surface here in Rome

It is now time to ask your expert opinion on the inner workings of the DOF display on the Batis: as far as I know, the DOF calculation depends on the CoC (Circle of Confusion), which in turn depends on the image format.

Now, all the A7 cameras share the same FF image format, but they very much differ in sensor resolution; does this fact influence the acceptable CoC, and if so, does the Batis firmware apply the necessary corrections to its DOF computation?

 

[pegelli]

The approximation of DOF is only a function of output size and viewing distance. As far as I know sensor resolution doesn't influence the DOF of the final output (screen or print).

 

[ErikKaffehr]

Hi,

Yes, that is the case.

If you shoot crop frame, the image needs more enlargement so CoC would be smaller. The Batis lenses take this into account, AFAIK.

Best regards
Erik

The approximation of DOF is only a function of output size and viewing distance. As far as I know sensor resolution doesn't influence the DOF of the final output (screen or print).

 

[Barry Haines]

So I just bit the bullet and ordered one of the first Batis 25mm to surface here in Rome

It is now time to ask your expert opinion on the inner workings of the DOF display on the Batis: as far as I know, the DOF calculation depends on the CoC (Circle of Confusion), which in turn depends on the image format.

Now, all the A7 cameras share the same FF image format, but they very much differ in sensor resolution; does this fact influence the acceptable CoC, and if so, does the Batis firmware apply the necessary corrections to its DOF computation?

My understanding is that the DoF scale whether OLED or engraved on a particular fixed/prime FL lens stays the same no matter what the format is (FF or APS-C)...The CoC is calculated on what the lens can aspire to, not the size of the sensor or film (or any post cropping).

In fact several of the A7 series camera sensors are very slightly different in size from one another.

 

[dmward]

Looking at the iPhone App DOFMaster, written by Don Fleming, he lists the CoC diameter used by the calculator for each digital camera and various film sizes.
Based on this the CoC based on sensor size so the only adjustment would have to be when a camera is changed to APS-C. However, since that is a crop factor that is only applied to the in-camera JPG its likely that the lens, like those with engraved DoF scales, will only show the DoF for the full frame.

The difference between APS and 35mm film formats is .005mm so not a major consideration any way.

 

[Annna T]

The CoC is a constant that takes in account the magnification needed for a given output size, the distance of viewing and the negative/sensor format.

So the CoC is different for each format, because for the same output size and viewing distance smaller formats need more magnification.

As an example, for MFT, the size of the CoC is half that of the 35mm film format, because you need twice the magnification of a 35mm body to print at the same size.

The conventional CoC is based on quite restricting assumptions concerning the relationship between size of output and the viewing distance and recently I have seen some people claiming that with high pixels density, the CoC needed to be smaller. This also implies that you change the standard assumptions made with film : aka you accept that the viewer will get nearer to admire the details of a picture even if it is printed big. But you also have to use a high resolution printer.

At least his is my understanding. I bet that the Zeiss DOF scale is computed in the conventional manner like during film time.

 

[ErikKaffehr]

Hi,

That is my guess, too, more or less. I read an article by Dr. Nasse of Zeiss and he mentioned that they use a smaller CoC on some wide angles.

Best regards
Erik

At least his is my understanding. I bet that the Zeiss DOF scale is computed in the conventional manner like during film time.

 

[Barry Haines]

Hi,

That is my guess, too, more or less. I read an article by Dr. Nasse of Zeiss and he mentioned that they use a smaller CoC on some wide angles.

Best regards
Erik

That makes sense to what I read here a while back.
http://forum.mflenses.com/hyperfocal-distance-a-coc-for-the-21st-century-t48271.html

 

[pegelli]

I think any DOF calculation is an approximation since it calculates what can still be perceived as sharp by the human eye under a given set of circumstances.

Theoretically only one plane is in perfect focus and what can be perceived as sharp depends on the presentation medium (and surface), image size, viewing distance and the abilities of the viewer. Since neither of these are known by lens manufacturers they will use CoC assumptions that work OK "on average" but should never be taken as exact values.

Also when pixel peeping at 1:1 you might think pictures from a higher resolution sensor have less DOF vs. one from a lower resolution sensor but when you print the to the same size, same paper and view them from the same distance the difference is no longer visible and for practical purposes the DOF is the same (assuming the same aperture, lens and focus point).

 

[Barry Haines]

I think any DOF calculation is an approximation since it calculates what can still be perceived as sharp by the human eye under a given set of circumstances.

Theoretically only one plane is in perfect focus and what can be perceived as sharp depends on the presentation medium (and surface), image size, viewing distance and the abilities of the viewer. Since neither of these are known by lens manufacturers they will use CoC assumptions that work OK "on average" but should never be taken as exact values.

Also when pixel peeping at 1:1 you might think pictures from a higher resolution sensor have less DOF vs. one from a lower resolution sensor but when you print the to the same size, same paper and view them from the same distance the difference is no longer visible and for practical purposes the DOF is the same (assuming the same aperture, lens and focus point).

The perfect answer Pieter...I was just about to edit/add my post along the same lines as what you have just said :thumbs: :clap:

At the end of the day the only way is to run some tests with the Batis 25mm lens with your own camera and pixel peep or print out to see if you are happy enough to use/trust their DoF scales...It's all in the eye of the beholder what is acceptable or not

Now, all the A7 cameras share the same FF image format, but they very much differ in sensor resolution; does this fact influence the acceptable CoC, and if so, does the Batis firmware apply the necessary corrections to its DOF computation?

In all honesty, I think Zeiss themselves are probably the best people to ask to give you a definitive answer to your question.

 

[Annna T]

I looked at Zeiss German website, because for some lenses you can find DOF tables. I downloaded the Batis 25mm F2 "Datenblatt".

http://www.zeiss.de/content/dam/Photography/new/pdf/en/downloadcenter/datasheets_batis/batis_225.pdf


But here is what they say concerning DOF (English translation is theirs):

ZEISS Batis 2/25
Schärfentiefe / Depth of field (DoF)
Keine Angabe der Schärfentiefetabelle, da die Angaben vom verwendeten Kamerasensor abhängen. Schärfentiefewerte werden direkt am Display des Objektiv angezeigt.

No indication of depth of field, as data is depending on used camera sensor. Depth of field values are shown directly on the lens display.​

But they have DOF tables for the Loxia 21mm here :

http://www.zeiss.de/content/dam/Photography/new/pdf/en/downloadcenter/datasheets_loxia/loxia_2821.pdf

And there is a footnote explaining how they computed the table :

Depth-of-field table for sensor format 24x36mm, circle of confusion 0.030mm (D/1500), rounded to 0.01m​

Aka just the standard CoC of 0.03 for 24-36mm format.

 

[Barry Haines]

I looked at Zeiss German website, because for some lenses you can find DOF tables. I downloaded the Batis 25mm F2 "Datenblatt".

http://www.zeiss.de/content/dam/Photography/new/pdf/en/downloadcenter/datasheets_batis/batis_225.pdf


But here is what they say concerning DOF (English translation is theirs):

ZEISS Batis 2/25
Schärfentiefe / Depth of field (DoF)
Keine Angabe der Schärfentiefetabelle, da die Angaben vom verwendeten Kamerasensor abhängen. Schärfentiefewerte werden direkt am Display des Objektiv angezeigt.

No indication of depth of field, as data is depending on used camera sensor. Depth of field values are shown directly on the lens display.​

But they have DOF tables for the Loxia 21mm here :

http://www.zeiss.de/content/dam/Photography/new/pdf/en/downloadcenter/datasheets_loxia/loxia_2821.pdf

And there is a footnote explaining how they computed the table :

Depth-of-field table for sensor format 24x36mm, circle of confusion 0.030mm (D/1500), rounded to 0.01m​

Aka just the standard CoC of 0.03 for 24-36mm format.

Thanks for that Annna, so just to recap...
We now have 4 different types of Zeiss 21mm F2.8 designed lenses, which have at least 3 completely different CoC values for 36x24mm...
The Milvus 21mm and Loxia 21mm show 2 completely different DoF tables
This is why I carry out my own set of tests at the end of the day of what I deem acceptable or not
___________________________________________
Loxia (E mount) flavour...
http://www.zeiss.co.uk/content/dam/...ownloadcenter/datasheets_loxia/loxia_2821.pdf
Depth of field table for sensor format 24x36mm, circle of confusion 0.030mm (D/1500), rounded to 0.01m
As also confirmed on Zeiss UK (Eng)
___________________________________________
Milvus (ZE/ZF.2 mount)
http://www.zeiss.co.uk/content/dam/...wnloadcenter/datasheets_milvus/milvus2821.pdf
Depth of field table for sensor format 24x36mm, circle of confusion 0.033mm (D/1500), rounded to 0.01m
___________________________________________
Original Classic (ZE/ZF.2 mount)
Hyperfocal distance: a CoC for the 21st century
Traditionally, a circle of confusion of 0.03mm is used in depth of field charts or calculators.
The DoF scale engraved on manual lenses, also uses this value.
Carl Zeiss wrote:
When a 21mm lens is focused at 2m and f/8, the DOF goes up to 34m (with a circle of confusion of 0.03mm), but reaches not infinity. If a more critical circle of confusion (0.015mm) is used which is much more realistic for the criteria when looking at a 21MP image at 100%, the depth of field is even shallower.
So it is not possible to get a sharp image at infinity when the lens was focused to 2m.
___________________________________________
No DoF scales that I can find for the ZM 21mm Biogon F2.8
http://www.zeiss.de/content/dam/Pho...enter/datasheets_zm/biogon_t_28_21_zm_ger.pdf
___________________________________________

 

[Massimo]

I looked at Zeiss German website, because for some lenses you can find DOF tables. I downloaded the Batis 25mm F2 "Datenblatt".

http://www.zeiss.de/content/dam/Photography/new/pdf/en/downloadcenter/datasheets_batis/batis_225.pdf


But here is what they say concerning DOF (English translation is theirs):

ZEISS Batis 2/25
Schärfentiefe / Depth of field (DoF)
Keine Angabe der Schärfentiefetabelle, da die Angaben vom verwendeten Kamerasensor abhängen. Schärfentiefewerte werden direkt am Display des Objektiv angezeigt.

No indication of depth of field, as data is depending on used camera sensor. Depth of field values are shown directly on the lens display.​

But they have DOF tables for the Loxia 21mm here :

http://www.zeiss.de/content/dam/Photography/new/pdf/en/downloadcenter/datasheets_loxia/loxia_2821.pdf

And there is a footnote explaining how they computed the table :

Depth-of-field table for sensor format 24x36mm, circle of confusion 0.030mm (D/1500), rounded to 0.01m​

Aka just the standard CoC of 0.03 for 24-36mm format.

I wish to thank all the members who participated in this thread, and special thanks to Annna T ... I think the two documents she linked to clarify well how Zeiss went about their OLED DOF algorithm: IMO they consider the CoC in the standard sense, without any regard to the pixel density of the sensor.

I am used to stop down further than what the DOF tables advise for a given landscape shot of mine, and I will still be doing the same with the Batis.

 

[Barry Haines]

I thought this was relevant to just add...
http://betterphotography.in/reviews/zeiss-batis-25mm-f2-zeiss-at-its-zenith/42851/

"The 25mm is the also the first lens in the world to move away from the standard methods of calculating DOF, by taking sensor resolution and lens characteristics at different apertures into account. This is not mentioned anywhere in Zeiss factsheets. DOF calculation with the Sony Alpha 7R II is constrained to ensure that the zone of sharpness remains acceptably so, with the image being viewed at 100%. Given the same apertures, and depending on the camera used (from the Alpha 7 series), the Batis will display different DOF distances. For the purist, this is a huge leap forward."

 

[pegelli]

For the purist, this is a huge leap forward."

Barry thanks for the link and quoting this piece. I always thought the purists were the people that only looked at the final output presentation but now it seems pixel peepers are suddenly promoted to purists :ROTFL:

 

[Lars]

So... 0.03 mm CoC on 24x36 mm translates to 800x1200.
Still relevant?

 

[Annna T]

I read a little on the concept of DOF and CoC this morning :

Concerning DOF :
https://en.m.wikipedia.org/wiki/Depth_of_field
(There is an interesting paragraph concerning the relationship between DOF and format)

and concerning CoC
https://en.m.wikipedia.org/wiki/Circle_of_confusion

Someone earlier in this thread wrote that Zeiss was using D/1730 as opposed to D/1500 as the CoC.

Here is what one can read about the size of the CoC in the wikipedia pages linked above :

Using the “Zeiss formula”, the circle of confusion is sometimes calculated as d/1730 where d is the diagonal measure of the original image (the camera format). For full-frame 35 mm format (24 mm × 36 mm, 43 mm diagonal) this comes out to be 0.025 mm. A more widely used CoC is d/1500, or 0.029 mm for full-frame 35 mm format, which corresponds to resolving 5 lines per millimeter on a print of 30 cm diagonal. Values of 0.030 mm and 0.033 mm are also common for full-frame 35 mm format. For practical purposes, d/1730, a final-image CoC of 0.2 mm, and d/1500 give very similar results.​

But here is what I found about that Zeiss formula : it has nothing to do with the Zeiss Manufacture, but only with the fact that the tests conducted to compute that result were made using a Zeiss lens, as is explained there :

https://en.m.wikipedia.org/wiki/Zeiss_formula

Extract :

The Zeiss formula is apocryphal, in the sense that it has grown to be a well-known named concept by propagation through the internet, even though it has no official origin, little connection to Carl Zeiss Company, and no recognition or usage in the photographic industry outside the web community.​

 

[Barry Haines]

So... 0.03 mm CoC on 24x36 mm translates to 800x1200.
Still relevant?

I think I follow you...24x36mm divided by a CoC value of 0.03mm which would indeed give you 800x1200

It is well explained with examples on Wiki https://en.wikipedia.org/wiki/Circle_of_confusion

Or in case of Zeiss lenses you can just accept the figure that they give you from their website for each individual lens, it normally slightly fluctuates between their lenses which is commonly between 0.029mm and 0.033mm

For example
Click on the Loxia 21mm Link http://www.zeiss.co.uk/content/dam/...ownloadcenter/datasheets_loxia/loxia_2821.pdf

At the bottom of the PDF you have a DOF scale and at the bottom of that you will find the small print, which should read as...

Depth of field table for sensor format 24x36mm, circle of confusion 0.030mm (D/1500), rounded to 0.01m

Once you have the CoC value for a specific lens you can run that value through a third party program like DOFMASTER.

DOFMASTER is a good one that you can even add an app to your iphone Hyperfocal Distance and Depth of Field Calculator - DOFMaster

Click on...
For the calculator Online Depth of Field Calculator

or alternatively for a more detailed DoF table than what Zeiss gives you for printing out Depth of Field Table

Now enter the CoC value which you will find by scrolling to the bottom of the selection.
Now add the Focal length (mm), Selected f-stop and Subject distance (in a choice of metres or feet) then click calculate

This will now give you the all important hyperfocal distance to set on your lens

Cheers Barry

 

[Massimo]

I thought this was relevant to just add...
http://betterphotography.in/reviews/zeiss-batis-25mm-f2-zeiss-at-its-zenith/42851/

"The 25mm is the also the first lens in the world to move away from the standard methods of calculating DOF, by taking sensor resolution and lens characteristics at different apertures into account. This is not mentioned anywhere in Zeiss factsheets. DOF calculation with the Sony Alpha 7R II is constrained to ensure that the zone of sharpness remains acceptably so, with the image being viewed at 100%. Given the same apertures, and depending on the camera used (from the Alpha 7 series), the Batis will display different DOF distances. For the purist, this is a huge leap forward."

This is very, very interesting
Thank you Barry.

 

[Barry Haines]

This is very, very interesting
Thank you Barry.

You are most welcome Massimo...I like a challenge and didn’t want to particularly give up on finding the correct answer for you.
I have been continuing with the search because I was also intrigued how the Batis 25mm OLED DoF scale is computed.

After quite a bit of digging about, I have just found this, which I think is exactly what you wanted to know all along

ZEISS Batis lenses – Display Settings – LENSPIRE – The new ZEISS photography platform

See the 4 Responses on the right hand side

(The CoC value it seems is completely different from the conventional 0.03mm)

____________________________

Tarmo
18. October 2015 22:24
What definition of “sharp focus range” do you use in the Batis lens DoF measurest? Does it somehow take sensor resolution into account and indicate truly sharp range, or is it based on the classic “adequate” value, which is much below modern sensor resolution?

____________________________

ZEISS LENSPIRE Team
19. October 2015 11:57
Hi Tarmo,
We’ll get back to you about your question asap!
Your ZEISS LENSPIRE Team

____________________________

ZEISS LENSPIRE Team
20. October 2015 16:43
Hi Tarmo,
Depending on the camera model/sensor type/sensor resolution, the Batis display will show the DOF data coming from the camera body, based on critical circles of confusion in a range between 0.012 and 0.015 millimeters.
So the DOF data shown on a Batis display depends on the camera type/sensor resolution, the aperture setting and focusing distance.
Your ZEISS LENSPIRE Team

___________________________

Tarmo
24. October 2015 7:15
Thank you for the reply! That is a vastly superior method to the traditional dof scales.

___________________________

That concludes my search, I must get a life and some sleep :ROTFL:
Hope that helps...Cheers Barry