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REQUEST = M9 & M8 bokeh/DOF comparison


usccharles

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Hi,

 

I so i keep hearing from people that the DOF for a given lens (say at f/1.4) is different on a cropped sensor compared to a FF sensor, that actually there is more depth of field on the cropped sensor compared to a FF sensor, even though it is shot with the same lens and at the same aperture.

 

Is this true? personally i don't see how a cropped sensor can affect DOF a lens creates for a given aperture.

 

any body with both M8 and M9, and a wide aperture lens, care to take a comparision shoot??

 

thanks :)

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There is less:

DoF is smaller while focal length is larger (bigger lenses) and/or Larger apertures used (F=1.4, 1.0 etc) which means more oof areas or more Bokeh as you all say

 

So, if you have the same lens, you get more bokeh with M8

 

Edit: Ah, remember that DoF is a zone of 2 distances like: s1-s2. The smaller the difference the more the oof areas in your shots

Edited by diogenis
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So, if you have the same lens, you get more bokeh with M8

 

Actually i think you got that backwards, the smaller the sensor the more DoF. Larger sensor you have an easier time blurring out the background, try shooting at f 2 on a medium format camera focal plane is extremely narrow. For that reason the S2 would make for a difficult camer a to documentary work as would have to stop down to f/16 to put a lot in focus but with out high ISO support it becomes much more a challenge.

 

Just like aperture, stop down (make smaller) more in focus, open up (make bigger) and small area in focus...

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Imho, the evaluation of DOF must be done for a CERTAIN subject taken into the same frame M8 and M9, so the question is this :

 

- With M8, for having a certain frame of a certain subject, you have to use, for instance, a 35 mm lens

- With M9, to have the same frame, you must use a 50 mm -----> less DOF.

 

It has always been so, even at film's times... Large Format cameras had "movements" for film plane and lens plate to achieve the needed DOF, for they need long focals and the issue was often significant, much more than with 35 mm film cameras.

Edited by luigi bertolotti
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Dof is quite complicated, mathematically speaking. The Wikipedia article is quite interesting, but be prepared to delve back into what you were taught about algebra in your youth. Anyway, eyeballing it is good enough for practical photographers.

 

Depth of field - Wikipedia, the free encyclopedia

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Actually i think you got that backwards, the smaller the sensor the more DoF. Larger sensor you have an easier time blurring out the background, try shooting at f 2 on a medium format camera focal plane is extremely narrow. For that reason the S2 would make for a difficult camer a to documentary work as would have to stop down to f/16 to put a lot in focus but with out high ISO support it becomes much more a challenge.

 

Just like aperture, stop down (make smaller) more in focus, open up (make bigger) and small area in focus...

 

DoF has nothing to do with sensor sizes.

DoF as Jaap indicates into his link is only relevant to focal lens distances and lens Apertures used. If you keep Aperture constant, and only play with lenses, you get LESS dof the bigger the lens. Less DoF means more bokeh or oof areas.

Now if you have two cameras say an M8 and an M9, and the same lens 50mm and same aperture F=1.4, then because of the crop thingy of the M8 (1.33x) the same 50mm lens gets bigger and so you get more bokeh.

But if you used the 35mm on the M8 and the 50mm on the M9, the bokeh would be the same, the DoF would be the same

 

Edit: one more time: DoF is an area or a zone that is calulated by two distances. Wiki refers to them as Sf -Sn for far and near in focus distances. So the less this difference is the less the DoF zone and the more bokeh

Edited by diogenis
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And subject distance, don't forget that! Having said that, if you go for the least simplified formula (which isn't in the Wiki article), there is a parameter for receptor size introduced. However it is better ignored.

More relevant is that the standarized COC value is far too large for present-day digital photography. I would advocate 0.015 for full format.

Edited by jaapv
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I won't get into the confusion of circles - but there is a difference between what is apparently sharp or not (Depth of field), and how much the background or foreground that is obviously blurred - is blurred. And the character of that blur. (bo-ke)

 

I can shoot a picture with a 35 @ f/1.4 on either M8 or M9 - where there is obviously only a single plane that is perfectly sharp. But the most extreme blurs will still be fairly small overall.

 

Conversely, I can shoot a picture with a 135 @ f/5.6, and get, say, most of a face all sharp, but with a much more strongly blurred background.

 

Your basic intuition is right, that at the moment of capture, the image thrown on the sensor (of any size) is the same from any given lens. Things are sharp - or they aren't.

 

From this point on, a lot of other factors come into play. Would you really use the same lens on the M8 and the M9, from the same shooting spot - and accept two different compositions - or would you move back with the M8 to get the same framing as the M9. That move will affect final DoF.

 

Or would you swap lenses, to get the same framing from the same spot? I.E. a 50mm on the M8 and a 75mm on the M9. That change also affects DoF.

 

If you shoot with the M8, you start with a 18 x 27mm image. To get to a 180 x 270mm print, you enalrge it 10x. From the M9, you start with a 24 x 36 image, and for the same print you'd enlarge it only 7.5x. So there will be almost sharp spots that still look sharp with only a 7.5x enlargement, but are 1.33x more visibly blurry with 10x enlargement.

 

I.E. the dynamics of final DoF in the final print depend on many variables.

 

That's the broad-brush idea. I'll leave the two pages of various detailed calculations to others. Some day, I won't bother to actually take a picture - I'll just frame the DoF calculations instead.

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Is this true? personally i don't see how a cropped sensor can affect DOF a lens creates for a given aperture.

Sure it’s true. There is no such thing as the depth of field of a lens, just a depth of field in an image. The DoF is defined as the zone of acceptable sharpness which in turn is specified as a maximum acceptable circle of confusion. There are several ways of determining how big the circle of confusion can get without compromising apparent sharpness, but the standard way is to take the image diagonal and divide it by some factor – 1500 is commonly used, though one might argue that in digital photography, one should divide by 2000 or more. But whatever the divisor, the circle of confusion depends on the image – i.e. sensor – size, and so does the depth of field in the image.

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So, in short and to simplify things:

You got a series of lens with your M8/M9?

The bigger the lens, the more the Bokeh ;)

 

My problem is not the bokeh. My problem is which color should I go for: the anthracite or the black? ? I had decided but now someone said the anthracite is not nice :(

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whoa lots of difficult terms... my head hurts... examples would be good~ :)

 

The problem with all this is that there are an infinite number of variables that go into making an image and the bokeh effect that follows from it: every now and again I'm busy congratulating myself on the lovely OOF effect from the Nocti on the M8, thinking this or that effect wouldn't be possible on a smaller sensor camera, and then darnit if my eye doesn't fall on an image from my RD1s with the cheapy Canon 1,2 that has an even nicer effect!

 

And then the M8 + Jupiter3 almost refuses to take a photograph without the little devil throwing masses of bubble bokeh everywhere (which for some reason I love).

 

So the arguments about sensor-size alone are (as usual) a gross simplification of the processes involved.

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Ok I am trying to interpret yoiu here, so I might be wrong. By asking:

Hi,

 

I so i keep hearing from people that the DOF for a given lens (say at f/1.4) is different on a cropped sensor compared to a FF sensor, that actually there is more depth of field on the cropped sensor compared to a FF sensor, even though it is shot with the same lens and at the same aperture.

 

Is this true? personally i don't see how a cropped sensor can affect DOF a lens creates for a given aperture.

 

any body with both M8 and M9, and a wide aperture lens, care to take a comparision shoot??

 

thanks :)

To me it seems that you confuse DoF with blurring or Bokeh you get because of DoF.

If this is the case then:

 

The answer is that yes, the M8 gives you more Bokeh to your images with the same Lenses/Apertures used. It certainly IS different.

 

If you really meant DoF on the first place then the correct answer for M8 is that it gives you LESS DoF

 

 

In any way, whatever camera you might have and because all these are irrelevant when you take pictures, you simply need to know that:

You get more blur (or Bokeh) or Less DoF the bigger the lens you use AND/OR the bigger the aperture

 

 

Edit: Just try to imagine DoF as a moving stripe or area in front of you, that is defined (how big or small it is) by the lens you use and aperture, and that within it everything is in focus.

Edited by diogenis
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whoa lots of difficult terms... my head hurts... examples would be good~ :)

 

Indeed, amazing how much ernst pontification this subject generates, be it now in Leica circles, a few years ago in Nikon circles, or no doubt before that in Canon cirlces.

Talk about circles of confusion.

 

I dont have an M9 so cant help with samples from that. However a few years ago I did my own comparison of APS and FF, same tripod position, same subject, same aperture shot with a 300mm on FF and a 200mm on APS to give the same framing.

The FF had much shallower DOF and a steeper transition to OOF.

I guess the effect is somewhat exaggerated with these long lenses and maybe would be less apparent at Leica M typical focal lengths.

 

Like you say, where are those examples!? :D

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Ok I am trying to interpret yoiu here, so I might be wrong. By asking:

 

To me it seems that you confuse DoF with blurring or Bokeh you get because of DoF.

If this is the case then:

 

The answer is that yes, the M8 gives you more Bokeh to your images with the same Lenses/Apertures used. It certainly IS different.

 

If you really meant DoF on the first place then the correct answer for M8 is that it gives you LESS DoF

 

 

In any way, whatever camera you might have and because all these are irrelevant when you take pictures, you simply need to know that:

You get more blur (or Bokeh) or Less DoF the bigger the lens you use AND/OR the bigger the aperture

 

Yes this is true, I was simply being anecdotal. I meant by my rambling that a photograph is more than a scientific table of numbers: lighting, dof, (mostly) lens, background, closeness to the subject and so on; these are all more critical imho than simply sensor size.

 

My edit: I just saw your additional edit - no need to explain Depth of Field. We're mostly not newbies here. I'm sorry I strayed from your scientific investigation of which camera will give you the narrowest 'stripe' of focus.

Edited by plasticman
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whoa lots of difficult terms... my head hurts... examples would be good~ :)

Actually you don’t even need M8/M9 comparison shots; just about any image taken with any camera would do the trick.

 

Take two prints of the same image, say a portrait shot, then crop one to 0.75 the size (representative of the M8 with its 1.33 crop factor). If you are looking at the larger, non-cropped image, you will view it from a typical viewing distance so you can appreciate the image in its entirety. You will come to the conclusion that, say, the eyes are in focus and that the tip of the nose and some strands of hair are still acceptably sharp and thus within the depth of field.

 

Now replace this image with the smaller, cropped image, and try again. As the image is smaller, you will prefer to look at it from a closer distance, so you take a step forward. This allows you to discern more detail, but also some slight blurriness that you didn’t notice before, when you were watching the exact same detail – it’s just a crop from the original image after all, so nothing has changed – from a larger distance. Now it appears to you that the tip of the nose isn’t quite that sharp, and some hair you initially judged to be sharp is actually a bit blurry. So the depth of field has become more shallow, even when nothing in the image itself has changed.

 

Obviously this result depends on the assumption that for the purposes of determining depth of field, acceptable sharpness should be defined based on what detail a typical viewer watching an image from a typical viewing distance (usually assumed to be the image diagonal) can still discern. This is in fact the standard assumption for depth of field calculations. One could still apply other standards, for example the “pixel-peeper standard” that defines acceptable sharpness as the maximum sharpness a given camera can deliver, leading to markedly different results. It is not like depth of field was some scientific term with a fixed meaning; rather it’s a measure defined pragmatically and its precise definition does and should depend on one’s requirements.

Edited by mjh
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.

 

My edit: I just saw your additional edit - no need to explain Depth of Field. We're mostly not newbies here. I'm sorry I strayed from your scientific investigation of which camera will give you the narrowest 'stripe' of focus.

Now that is an interesting remark. The "stripe of thickness" as you call it refers to what I term the "native DOF"of the sensor, where the enlargement is so high that the COC gets the same size (or smaller) than the pixel size. I found that with the 24 Summilux on the M8 that amounts to about 15 mm at 3 m. Mathematically inclined members will no doubt be able to calculate the exact value. On the M8 and on the M9 the pixel size is identical, so that value should be identical too.

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there is no difference in dof between the M8 and M9 sensors for any given lens

 

true enough in itself, but only relevant if you never actually look at your photos.

 

As MJH has pointed out above, how pictures are viewed also effects percieved DOF, and as a smaller sensor is, by definition, smaller the image it captures has to be enlarged more for a given viewing size.

So for a given subject, framed the same way with M8 and M9, either you use a wider lens on the M8 or you move further away, hence you get more DOF from the lens. But then to get the same viewing size you enlarge the M8 image more, and in doing so reduce the DOF.

Calculations suggest you get less DOF, for a given AOV and print size, from an APS sensor than FF. But my experiement as mentioned aboved showed the opposite. Since I am more interested in photos than maths, I'll stick with the results I see.

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So for a given subject, framed the same way with M8 and M9, either you use a wider lens on the M8 or you move further away, hence you get more DOF from the lens. But then to get the same viewing size you enlarge the M8 image more, and in doing so reduce the DOF.

Calculations suggest you get less DOF, for a given AOV and print size, from an APS sensor than FF. But my experiement as mentioned aboved showed the opposite. Since I am more interested in photos than maths, I'll stick with the results I see.

If you opt for a shorter focal length with the crop sensor to make up for its smaller angle of view, there are two opposing effects influencing depth of field: everything else being equal, a shorter focal length would increase DoF, while a smaller sensor (and thus smaller CoC / higher magnification), again everything else being equal, would result in a more shallow DoF. As the influence of the focal length is greater than that of the CoC (mathematically the CoC is a linear term in the DoF formula while the focal length is squared), in the end you will get more depth of field. So the theory is actually in agreement with your visual results.

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