Depth of field comparison XF 56 vs XF 90

[nzl]

I have looked everywhere I can think of to see if there is a depth of field comparison between the XF 56 and the XF 90 for taking a similarly framed photo - i.e. a head and shoulders photo or full length photo where the subject takes the same amount of space in the final photo.  For this to occur obviously the distance from the camera to the subject would need to change given the different focal lengths of the lenses and I don't know how much impact this would have.  I can imagine the XF 56mm may have the shallower depth of field because of the faster aperture and closer focus distance but then again the XF 90mm may have the shallower depth of field because of the longer focal length of the lens, even though it has a slightly slower maximum aperture and further distance from the subject.  

 

I don't know if there are formulae for these calculations, I have only seen formulae where the subject and the camera are the same distance apart and I don't know how much impact the narrower field of view of the longer lens would cause you to move back.  It may be possible that for close up photos one lens has shallower depth of field and it swaps around as you move further away.

 

Obviously depth of field is not everything.  The 56mm will be better suited to indoors where there is typically less light and less space and will give a different 'look' compared to the 90mm.  I am just not sure which look I prefer between the 56mm and 90mm.

 

Thanks for any tips.

[CRAusmus]

Sounds like a perfect excuse to go to a local shop and try them both out....

[val]

I've tried out both and I prefer the 90mm, I don't have any samples to share though.

[Tikcus]

http://fujifilmxmount.com/comparison/en/test-our-lenses/?o=XF56

edit

 

seems that the 90 is not listed, but you can compare others

[nzl]

Sounds like a perfect excuse to go to a local shop and try them both out....

I have thought of this myself but it is reasonably difficult in New Zealand to find shops that regularly have both of these lenses in stock and even if they do i then need to find someone or something to stand still and be photographed several times.  It also relies on me to be able to frame accurately from one photo to the next which is dubious.

[nzl]

http://fujifilmxmount.com/comparison/en/test-our-lenses/?o=XF56

edit

 

seems that the 90 is not listed, but you can compare others

Yeah, I have used this before and found it interesting but the way these photos are taken the photos are taken from the same position and the subject obviously stays static as well so as you move from lens to lens you get different content in the photos because the field of view changes.  I was hoping there might be something online like this tool, or even some simple calculations, where the subject (say the crown) fills the same amount of the photo for each lens.

[frod]

http://howmuchblur.com/#compare-1.5x-90mm-f2-and-1.5x-56mm-f1.2-on-a-0.9m-wide-subject

 

Of course, bokeh quality is subjective and neither of these lenses are at their sharpest wide open.

[quincy]

This might help:

http://dofsimulator.net/en/

 

 

Otherwise, you could always rearrange the equations found on wikipedia or in books on optics. You'll end up with something that looks like

 

T = {2*(f^2)*g*k*Z*(f-g)}/{(f^4)-(k^2)*(Z^2)*[(f-g)^2]}

 

or

 

T = 2*k*Z*{g*(g-f)}/{(f^2)-[k*Z*(g-f)/f]^2}

 

depending on what assumptions and simplifications you make. You'll then have to either calculate your object distance depending on the focal lenght to get the same magnification before you insert it into the formula, or you could replace the object distance from the formula by a term that gives you the relation between object distance, focal lenght and magnification. (Should be a simple angular relation)

 

 

With

T: Depth of Field

k: Aperture (f-stop)

Z: acceptable circle of confusion (determined by e.g. pixel size)

g: object distance (from the center of your optical system, not from the sensor)

f: focal lenght

[val]

Proof that I had the gear to do this test

 

DSCF2010 by Will Solis, on Flickr

 

90mm F2 at F2

 

DSCF7038 by Will Solis, on Flickr

 

56mm F1.2 at F1.2

 

DSCF7039 by Will Solis, on Flickr

I chose the bag because its the closest thing I have to a human head size.

 

I prefer the compression of the 90mm but both are good

[mdm]

The picture taken by 56f1.2 looks underexposed and a bit out of focus.

[johant]

The picture taken by 56f1.2 looks underexposed and a bit out of focus.

 

Maybe, but they were very useful to me.

[andrewv8]

I just got the 56... I love it.  Haven't taken it off the camera in a week.  I wouldn't hesitate to recommend it.  I was also torn between the 56 and the 90... I decided that the 90 was just sooo big and the 56 was more versatile in that it has reach but can still be used as a walkin around lens.... + that 1.2 is just unreal. 

[nzl]

This might help:

http://dofsimulator.net/en/

 

 

Otherwise, you could always rearrange the equations found on wikipedia or in books on optics. You'll end up with something that looks like

 

T = {2*(f^2)*g*k*Z*(f-g)}/{(f^4)-(k^2)*(Z^2)*[(f-g)^2]}

 

or

 

T = 2*k*Z*{g*(g-f)}/{(f^2)-[k*Z*(g-f)/f]^2}

 

depending on what assumptions and simplifications you make. You'll then have to either calculate your object distance depending on the focal lenght to get the same magnification before you insert it into the formula, or you could replace the object distance from the formula by a term that gives you the relation between object distance, focal lenght and magnification. (Should be a simple angular relation)

 

 

With

T: Depth of Field

k: Aperture (f-stop)

Z: acceptable circle of confusion (determined by e.g. pixel size)

g: object distance (from the center of your optical system, not from the sensor)

f: focal lenght

 

Thanks, this is exactly what I was hoping someone would have done and done far more comprehensively than I could ever have imagined doing myself.  Extremely versatile website and after doing some various testing it shows that for a 'locked frame' as they call it, where the size of the subject remains constant, the 56mm has a shallower depth of field than the 90mm.  As many others have noted the difference in perspective between photos from the two lenses is more pronounced in the simulations that the difference in depth of field but good to know that you don't need the longer focal length to get the shallow depth of field.  As much as I want the reported sharpness and quick focusing of the 90mm I think the first one I will buy will be the 56mm given the increased flexibility of the faster aperture and increased versatility from the smaller size.  I suspect the 90mm won't be far behind though.....

 

Thanks again for all of your comments.

[sir_c]

I only have the 56 and I like it a lot. The 90 does have the edge, also in sharpness. But the focal length is difficult for me. The 56 is already hard to use indoors, you get very tight shots. Just imagine the XF 90 here.

I think those kind of parameters are more important in deciding between the two than the quality of the blur or lens sharpness. The latter two are so close that you must think well of you use cases.

[aladroer]

I have both. The 90 is clearly better in terms of definition and focusing speed. Pictures made with it really stand out. But it has a big "con" vs. the 56, at least for me: Not being stabilized, as soon as light dims, you have to start raising ISO, losing the advantage gained with its better definition. You have not only a difference of 1,5 stops in terms of aperture but, on top, you have to shoot at a higher speed, which represents 2/3 of stop less light. Therefore, shooting hanheld, the XF 56 has an advantage of, at least, 2 stops of light.

[JLR]

But it has a big "con" vs. the 56, at least for me: Not being stabilized, as soon as light dims, you have to start raising ISO, losing the advantage gained with its better definition.

The 56 isn’t a stabilized lens either, but maybe you meant that if the 90 *was* stabilized it’d give you similar capabilities in terms of real-world ability to gather light?

 

I have the 56 and love the images it can produce, but find the slow autofocus an endless source of frustration on my X-T1. Not sure if it performs better on newer cameras. I also wish it could focus closer, I always find myself surprised that I’m too close to a subject and get a failed focus. Of course, it’s meant for portraiture, so I understand why Fuji sacrificed that if they needed to keep the size/weight down. Still, would’ve loved if it was speedier/ more versatile so I could have a 1.2 walkaround lens.

[Dwight]

I have the 56 and love it as well. Yes, there are limitations, but that's true of any lens. I get extremely sharp images at 1.2 and have few problems with focusing. For me, the 90mm is too long a focal length to work with on a regular basis as I shoot mostly weddings and can sometimes work in close quarters. I don't use it much at the reception as the focusing is slower, but my 35 f/2 is the right tool as is my 12mm Zeiss. I have a pawn shop Olympus 50mm 1.4 OM lens that is amazing matched up to either of my Fuji bodies, so it's a matter of what you are trying to do and the results you like. I also have a Jupiter 85mm f/2 that's amazing; round aperture blades, but you really have to be on your "A" game to make it sing. The beauty of this time is that you can use literally any lens of your liking, so don't limit yourself. I'm kinda spoiled by the autofocus technology but at one point, I shot large format, so I learned patience

[hjalmarg1]

I had the 90mm and it is in many aspects better than the 56mm, however I found more versatile the 56mm for my common uses, so I sold the 90mm and kept the 56mm.

Bokeh is very good with both but the extra stop, weight and size inclined me to keep the 56mm. 90mm provides more compression, focus faster and it's WR

[Hermelin]

I enjoy my 90. Fast AF, optically perfect. But yeah it's kinda big, and and it needs pretty fast shutterspeed. Shot from today.

 

Shot at f/2. ISO 2500. What would the ISO be @ f/1.2?

 

Edited September 24, 2017 by Hermelin