Fuji X Lenses

[Slobodan Blagojevic]

There is really no need to mix sensel sizes to this at all. Everything related to DOF and sensor/film size can be calculated with basic geometry and/or visualized by using a ruler and a pencil. There is nothing esoteric about it, nor even a camera, film or sensor are needed at all. Just use a DOF calculator if you skipped geometry in school...

Seriously!?

[Petrus]

Seriously!?

Ray angles from points in focus and out-of-focus, determined by the distance, focal length and aperture. Maximum allowed circle of confusion determined from viewing distance, enlargement factor and definition of sharpness. No film, sensor, sensels needed, just paper an pencil. If you want to visualize it, use a ruler.

[Martin Ranger]

The bigger your sensor, the bigger the IQ (and the tinnier is your wallet... but it's always been like that).

Yay, the format wars have moved from the Medium Format Forum to Compact System Cameras. It was only a matter of time, I suppose. Now all repeat after me: "My sensor is bigger than yours". 

One day I went to a photographer to learn more, just with my DP2s (http://www.francois-rommens-photographie.fr/ and http://www.sensual-photography.eu/index.php?lg=fr). This photographer allowed me to use MF, 4x5 and 5D2 with 90TS and said : Once you will taste bigger sensor, you'll never come back... proof in the picture. He was right. Now, especially in my workshops, I prove it "by the picture" to my patients and it always work (and will always work).

Have a close look at sensual photography and come here saying me that you can achieve the same rendering without PP with your XT-1

Now I have some clients to take care of. See you later.

Actually, unless all the FF photos on the sensual-photography website are shot wide open, the look of them can be achieved with an APS-C camera. Now film MF or even 4x5 is a different matter. If you want to argue that FF allows you to get shallower DOF and you absolutely need it for your images, I don't thing anyone is going to argue with you. Making blanket statements about bokeh and formats, on the other hand, is hyperbole.

All IMO of course.

[Slobodan Blagojevic]

Ray angles from points in focus and out-of-focus, determined by the distance, focal length and aperture. Maximum allowed circle of confusion determined from viewing distance, enlargement factor and definition of sharpness. No film, sensor, sensels needed, just paper an pencil. If you want to visualize it, use a ruler.

Ah, the fly in your ointment: the definition of sharpness. In my post, I actually and directly quoted an explanation for the link between "the definition of sharpness" and circle of confusion that explains the role of sensor/sensel size. I even provided a link to the relevant article, written by a guy who is technically much smarter than I am (he holds a PhD in a related discipline).

[BJL]

... take a 200 mm F/2 lens and you mount it on a D750 and on D7100. Then you shot the same subject from the same position, which one will have more blur/less DOF?

I think that comparisons like this with very different field of view are of little practical interest.

I prefer comparing formats with "the same scene", meaning with the same camera position relative to the subjects, and the same field of view (same subjects in view, at the same positions relative to the composition as a whole, same apparent sizes, etc.). This of course involves the familiar pattern of focal length adjusted in proportion to linear format size.  Then there is simple guideline that is reasonably accurate (except at the extremes of very near or very far; where "very near" means magnification about 1/10 or larger and "very far" means focusing at or beyond hyperfocal distance):

With equal field of view and equal camera position relative to the subjects, the DOF is measured by the entrance pupil size, a.k.a. effective aperture diameter: focal length divided by aperture ratio.

This by the way means roughly equal lens size and weight, due to requiring the big front lens elements to be similar in size.  When a lens does not give shallow enough DOF even wide open, getting less DOF on the same scene always requires "bigger glass", whether by changing lens in the same format or by changing to a larger format.

The main way that format size comes into this is that the when using a larger format and proportionately longer focal length, the entrance pupil size needed to get a given DOF is achieved with a higher f-stop, making it easier for the lens to have good control of aberrations.

[BJL]

"The depth of field can be based on when the circle of confusion becomes larger than the size of your digital camera's pixels" (source: Cambridge in Color).

That measure of DOF might have its place, but it is quite different from the one that most photographers (and on-lens DOF scales) have been using for a century or more, so we should at least explain which version we are using when making claims.

That "CoC = pixel size" measures a "minimum depth of field": the distance from the plane of exact focus within which OOF effects are never to be seen, no matter how large you display the image and how closely one views it, due to any OOF effects being buried under sensor resolution limits.  The far more common concept is measuring the distance from exact focus beyond which OOF effects are visible under certain viewing conditions, with a certain ratio of image size to viewing distance and a certain level of visual acuity.  The latter is the version I was assuming in my previous post about entrance pupil size measuring DOF.

There is a potentially big gap between such measures of DOF and the extent of OOF effects on the background of an image. This "minimum DOF" is decreased by reducing the pixel size on a sensor of the same size, but that will have no effect on how strong the OOF effect is on subjects falling outside this "absolutely in-focus" region; in particular, smaller pixels will have no effect on how strong the OOF effects are on the background well behind the main subject, which is what people are commonly referring to of when they talk about "bokeh".

This is yet another case where "extent of background blur" and "depth of field" are not the same thing, so it is strange to read experienced photographers using "bokeh" to mean "DOF", and even strange to read "good bokeh" used to mean simply "shallow DOF".  Another example is the effect of moving back from the main subject and increasing the focal length (or cropping!) to keep its image occupying the same portion of the frame.  Because if you then adjust the aperture to give the same DOF, you will have more pronounced background blur.  (This move also decreases how much of the background is even visible, so for two reasons backing off can be useful for reducing the effects of a distracting background. I pity the portrait photographers working in cramped studios who have to spend a lot more on cameras and lenses to achieve the "background control" that an outdoor photographer like me can usually get by just taking a few step back!)

[Slobodan Blagojevic]

...it is strange to read experienced photographers using "bokeh" to mean "DOF", and even strange to read "good bokeh" used to mean simply "shallow DOF"...

Out of curiosity, which "experienced photographers" said that?

[barryfitzgerald]

Nobody said that I dislike the term "bokeh" anyway blur does the job nicely in my view
Depth of field is a technical aspect it does not always indicate how the rendering will fall it's possible to blur the background out significantly with a slower lens under the right conditions, sometimes a few stops in aperture don't make a huge difference to the background (for closer head shots esp true)

[BJL]

In response to my comment that

... it is strange to read experienced photographers using "bokeh" to mean "DOF", and even stranger to read "good bokeh" used to mean simply "shallow DOF".

Slobodan asks

Out of curiosity, which "experienced photographers" said that?

I certainly did not mean you, Slobodan! Surely you have seen this usage many times in forum discussions, and there seems to be a bit of it earlier in this thread:

You can't dream much about bokeh on an APS-C sensor, or you really need to shoot a bit close range with studied backgrounds (not to messy). Fighting with bokeh on APS-C is a vast waste of time.

Note that "close range" is good for reducing DOF, but moving further away and increasing focal length is instead more useful for increasing background blur.

[Manoli]

Thanks to BJL for that comprehensive dissertation on DOF. Seeing as this thread started off discussing FujiFilm aps-c and has meandered off to the inevitable MF v FF v APS discussion, perhaps it's worth putting things into a practical DOF context.

Rather than use the term DOF in the CoC/pixel size discussion, I prefer the term 'critical focus'. It's more descriptive.
Taking as an example the Fuji 56/1.2 and comparing it to a FF 85/1.4 - both focused at 3M,  Bart's on-line DOF planner gives the following DOF measurements:

<56>
f1.2:  3.70  - cms
f2 :    5.80 
f8  :   23.9
<85>
f1.4 : 1.64
f2 :    2.39
f2.8 : 3.37
f8 :    9.60

For portraiture, seeing as the 'average' head will have a DOF of at least 10 inches (25.4 cms), the minimum you'll need is an aps-c at f8, anything less and you'll need to be careful where you place that focus point ...

Despite the complaints it is possible to achieve satisfactory or shallow DOF on smaller formats (subject to faster apertures, distances)  ... As for Fuji some lenses like the 58mm F1.2 are designed to cater for those who want thin DOF and portraits

[Slobodan Blagojevic]

If the above table is correct, it seems that at NO POINT can an APS-C lens achieve the same shallow DOF as a full frame lens at 2.8?! It would need something like f/1.0, i.e., full three f/stops. Interesting. If you need more DOF, however...

[Manoli]

Yup, I'd say that's true but you've already got razor thin depth of field (actually critical focus, since the traditional DOF will include variables such as coc diameter, viewing distance, output size, visual acuity).

Here's the link to Bart's online DOF output quality planner.

[armand]

This is confusing. So DOF is dependent on the MPixels also not only on the sensor size?

A Nikon Df (16 MP) with the 85 mm at F/1.8 will have the same DOF as the Fuji X-T1 (16 MP) with the 56 mm at F/1.2.
If you use a higher megapixel camera, such as the D810, you will have less DOF. So for the opposite, if you need more DOF, a higher megapixel camera will be in disadvantage?! So I made the right choice choosing the D750 for landscape? 
Something doesn't add up.

[Hulyss]

DOF is a measurable constant. Bokeh regroup many other constants such as transitions. The bigger the sensor (and the color depth) the better is the bokeh (quality of the DOF). Strange fact is that all those formulas are not studied in art school (maybe roughly exposed) and I wonder why ? Maybe because they teach you how to get quality product out of YOU and not of the technical side of your camera (which is just an extension, a tool).

Just to disturb armand, a simple inexpensive Mamyia ZD (22MP), when used correctly, will give you far better pictures than your D750. How ? Well... I'm sure there is some associations around you that teach photo and own MF and even LF cameras. When you will try it, taste it, you will forget about those useless/endless forum conversations.

Now you need to find the willpower to go to register in this associations and finally, discovering/testing/experimenting the wide spectrum of photography tools. The goal is to open the eyes.

But armand, your avatar represent something interesting and I think some other over here should have a look at this

http://en.wikipedia.org/wiki/The_Myth_of_Sisyphus

"In the essay, Camus introduces his philosophy of the absurd: man's futile search for meaning, unity, and clarity in the face of an unintelligible world devoid of God and eternal truths or values."

See "God" and "eternal truths or values" as the deep meanings of photography. You'll never reach it, we'll never reach it, we'll never be able to describe nor quantify it. Today some peps think that DxO is god rofl !

This fact introduce another interesting constants such as Fatality and Resignation.
   
Back in the old days, I tried to convince Sisyphus, explaining him that even if he get the "truth" and the "meaning" he will not be more happy. I went to war, had children, accomplished things, got highs and downs... quite a full life, just accomplished my destiny while he was perpetually seeking ... seeking what ? This is the question I putted on the table one day he was resting. I brought him some goat cheese, wine and honey. Man... he was wreaked. His eyes was empty, stuck in time, empty of sense. He was unable to answer my question, unable to know what exactly he was seeking. He became crazy. Was a bad day, quite depressing to see a friend going this way, so far... I went on my own quest and I never seen him again.

[armand]

Again, it's not you who is able to create confusion here. For you bigger is better and I could care less to convince you otherwise as you seem happy with this knowledge.

In my experience with both APS-C and full frame you can get good results with both and others seem to agree with it. You go become famous with the Mamyia or whatever and I'll work with my own limitations.

PS. Your bokeh statements from prior posts (or this one before editing) were a little different than this last version; you remind me of Nikon, by correcting your mistakes without actually admitting to them 

[Petrus]

Why did we not fight over the effect film stock had on DOF in the good old days? Because nobody even thought film would matter at all, as DOF is an exact mathematical/optical phenomenon defined by a mathematical formula only.

If the sensor (film) resolution sets its own limits to sharpness, it has nothing to do with DOF calculations.

[JV]

In my experience with both APS-C and full frame you can get good results with both and others seem to agree with it.

+1.  For most people and for most applications (I am not saying for all) the differences in sensor size between MF, FF, APS-C and m43 will be completely negligible, certainly after post-processing.

[barryfitzgerald]

If the above table is correct, it seems that at NO POINT can an APS-C lens achieve the same shallow DOF as a full frame lens at 2.8?! It would need something like f/1.0, i.e., full three f/stops. Interesting. If you need more DOF, however...

It's about 1.3 stops difference from APS-C to FF roughly
Micro 4/3 is about 2 stops off FF DOF wise (shallow DOF)

The obvious variable here is the "distance to subject" you have to move back further with APS-C to get the same framing, even more so with micro 4/3
Real world I get similar DOF with my Fuji X10 to a bog standard kit lens for APS-C it's close enough (not quite but near) smaller sensor but faster lens speed lots of variables here

[BJL]

It's about 1.3 stops difference from APS-C to FF roughly
Micro 4/3 is about 2 stops off FF DOF wise (shallow DOF)

Sounds about right.

The obvious variable here is the "distance to subject" you have to move back further with APS-C to get the same framing, even more so with micro 4/3

Only if you use the same focal length in the different formats, which is not the way most of us do it.

[Slobodan Blagojevic]

It's about 1.3 stops difference...

2.8
2.0 - one stop difference
1.4 - two stop difference
1.0 - three stop difference