Depth of Field (Bokeh) lesson

[Ysarex]

But, and it is a big but, it would be true to say that if you were to take the same photo, (same fov, same subject distance), but this time say same dof, then the photo on the smaller sensor will always be shot using a wider aperture, (except macro of course).

And now you're arguing my position -- glad you agree with me. This is a simple corollary of the general rule that all else equal smaller format cameras produce deeper dof. So of course if you've adjusted a smaller format camera for what you require as sufficient DOF in a specific scene you can take the photo at a lower ISO and/or faster shutter speed than would be possible with a larger format camera which would have to be stopped down further to achieve the same sufficient DOF to take the same photo.

And that's a good reason why this general rule is valuable to photographers. That's exactly why my little 1/1.7 sensor compact remains my favorite camera for general walking around -- it's more versatile as the light dims and I don't have a tripod. I'll get sufficient DOF at f/3.2 for a successful photo that just wouldn't work with a larger format.

Joe

 

[Tim Tucker]

Or I guess you could just leave your professor hat on and continue to lecture to an empty classroom. Whatever floats your boat I guess. Have fun posting your charts and arguing moot points for no apparent reason.

Still waiting on you to offer a simple explanation as to why any of this would matter to your average photographer, or what benefit it would be to capturing better images. Lets just say I won't hold my breath.

I'm learning to look at things from a different viewpoint. Even though I do not communicate Ysarex's opinion I still read it all and find it interesting and I will question it. I don't see this as OCD, I just like to learn and Ysarex's viewpoint does make me look at things differently even if it doesn't convince me.

I'm sorry you find it boring and can only apologise.

But, and it is a big but, it would be true to say that if you were to take the same photo, (same fov, same subject distance), but this time say same dof, then the photo on the smaller sensor will always be shot using a wider aperture, (except macro of course).

And now you're arguing my position -- glad you agree with me. This is a simple corollary of the general rule that all else equal smaller format cameras produce deeper dof. So of course if you've adjusted a smaller format camera for what you require as sufficient DOF in a specific scene you can take the photo at a lower ISO and/or faster shutter speed than would be possible with a larger format camera which would have to be stopped down further to achieve the same sufficient DOF to take the same photo.

And that's why this general rule is valuable to photographers. That's exactly why my little 1/1.7 sensor compact remains my favorite camera for general walking around -- it's more versatile as the light dims and I don't have a tripod. I'll get sufficient DOF at f/3.2 for a successful photo that just wouldn't work with a larger format.

Joe

I do in part agree with you, it's just that the relationship is not fully reversible because there are some very real limits.

than would be possible with a larger format camera which would have to be stopped down further to achieve the same sufficient DOF to take the same photo.

Not in all cases, and not generally true with landscapes. From your own dof calculator (albeit the online version) we have the following which is not an uncommon situation in landscape:

As you can see the difference in dof between the two format sizes is only 5.5ft at the closest distance, and as you are aware the calculator is a guide that does not take into consideration the aberrations or the difference in the rendering of close focus between each lens and thus both can be considered as pretty close to equal. With both lenses set to f8 and the subject at 45ft with the closest object at 25ft then there is no difference in dof for the same photo. Further to that, in practical terms my 55/3.5 can focus to f16 without showing any softening from diffraction whereas the APS-C systems at 35mm generally exhibit it above f11.

(Practical application part), In landscape with my 55mm lens I usually achieve the dof need for the shot. If I can do that then the smaller sensor will not give any increase for the same photo. However with the crop sensor I'm able to do the same at a faster shutter speed and so can shoot while the wind is rustling the trees a little more.

If there are areas in front and behind the dof in the photo then your rule will always hold true. Once the focus point hits the hyper-focal point to infinity the increase in dof from the crop sensor ceases to be proportional to sensor size, once the larger format hits it there is little difference in dof (for the same photo). This is the practical limit and I find this very common in the style of photography that I enjoy. I can also quote text from many books and have posted a link that agrees with my position that Stroebel's rule has very real limitations.

In my own experience I've always found the reverse situation to be the problem. In the above example where the two formats have pretty much the same dof then opening up the lenses produces a change in dof that is not linear or proportional to sensor size. The larger sensor will reduce the dof far faster than the smaller one as Stroebel's rule comes into effect.

 

[The_Traveler]

This is a bit like walking away from a discussion at a New Year's party only to return the next year and find the discussion still going.

I will return if it gets to page 8.
Or if some big guys with clubs and guns show up at my house and force me.

 

[robbins.photo]

I'm learning to look at things from a different viewpoint. Even though I do not communicate Ysarex's opinion I still read it all and find it interesting and I will question it. I don't see this as OCD, I just like to learn and Ysarex's viewpoint does make me look at things differently even if it doesn't convince me.

I'm sorry you find it boring and can only apologise.

Well, I'll leave you guys to have the exact same argument you've had so many times before when the topic of bokeh comes up. When your done one upping each other, there's popcorn.

Laters.

 

[pixmedic]

Isn't bokeh that swirly stuff behind the subject?

 

[snowbear]

Isn't bokeh that swirly stuff behind the subject?

Either that or a brand of macha or sushi flavored ice cream.

 

[Ysarex]

But, and it is a big but, it would be true to say that if you were to take the same photo, (same fov, same subject distance), but this time say same dof, then the photo on the smaller sensor will always be shot using a wider aperture, (except macro of course).

And now you're arguing my position -- glad you agree with me. This is a simple corollary of the general rule that all else equal smaller format cameras produce deeper dof. So of course if you've adjusted a smaller format camera for what you require as sufficient DOF in a specific scene you can take the photo at a lower ISO and/or faster shutter speed than would be possible with a larger format camera which would have to be stopped down further to achieve the same sufficient DOF to take the same photo.

And that's why this general rule is valuable to photographers. That's exactly why my little 1/1.7 sensor compact remains my favorite camera for general walking around -- it's more versatile as the light dims and I don't have a tripod. I'll get sufficient DOF at f/3.2 for a successful photo that just wouldn't work with a larger format.

Joe

I do in part agree with you, it's just that the relationship is not fully reversible because there are some very real limits.

than would be possible with a larger format camera which would have to be stopped down further to achieve the same sufficient DOF to take the same photo.

Not in all cases, and not generally true with landscapes.

But generally true for general photography.

From your own dof calculator (albeit the online version) we have the following which is not an uncommon situation in landscape:

View attachment 131050

As you can see the difference in dof between the two format sizes is only 5.5ft at the closest distance, and as you are aware the calculator is a guide that does not take into consideration the aberrations or the difference in the rendering of close focus between each lens and thus both can be considered as pretty close to equal. With both lenses set to f8 and the subject at 45ft with the closest object at 25ft then there is no difference in dof for the same photo. Further to that, in practical terms my 55/3.5 can focus to f16 without showing any softening from diffraction whereas the APS-C systems at 35mm generally exhibit it above f11.

(Practical application part), In landscape with my 55mm lens I usually achieve the dof need for the shot. If I can do that then the smaller sensor will not give any increase for the same photo. However with the crop sensor I'm able to do the same at a faster shutter speed and so can shoot while the wind is rustling the trees a little more.

If there are areas in front and behind the dof in the photo then your rule will always hold true. Once the focus point hits the hyper-focal point to infinity the increase in dof from the crop sensor ceases to be proportional to sensor size, once the larger format hits it there is little difference in dof (for the same photo). This is the practical limit and I find this very common in the style of photography that I enjoy. I can also quote text from many books and have posted a link that agrees with my position that Stroebel's rule has very real limitations.

In my own experience I've always found the reverse situation to be the problem. In the above example where the two formats have pretty much the same dof then opening up the lenses produces a change in dof that is not linear or proportional to sensor size. The larger sensor will reduce the dof far faster than the smaller one as Stroebel's rule comes into effect.

This article addresses what's going on when you're near hyperfocal distance: Depth of Field and the Small-Sensor Digital Cameras
"Note that as the focus distance approaches the hyperfocal distance, DOF increases rapidly. Since this happens for the small-sensor camera with a 31.25mm lens first (because the hyperfocal distance is least), the ratio of the DOF of the small-sensor camera to that of full-frame sensor becomes larger than the ~1.6x that you would get if the lens was focused at a distance much shorter than the hyperfocal distance."

Like I said earlier "Obviously you can take a photo as in the 2nd example below where you have the DOF limits extending across the entire image -- I only needed to turn the APS camera horizontal and re-focus or stop the lens down further to do that. That does not negate the general rule, it simply means there are usage conditions in which it is not critical."

You like to take studied landscapes in which you commonly have your camera tripod mounted and DOF extending to infinity -- a usage condition which makes this rule not critical. Now take a break for a minute from the landscapes and become a general photographer. Lose the tripod. Photograph the kids in the pool, the dog in the house, friends in the backyard grilling burgers, scenes in the street, a shop window, soccer players in the park, a rose on the fence, a friend with her child, butterflies in the garden, a bottle of scotch, just a little of whatever and everything and sure a couple landscapes (no tripod). And if you heap thousands of such general photos together and compare with another heap of similar photos taken with a different format camera they'll be a DOF variance apparent between the two heaps. It will be due to the change in format.

Smaller format cameras as a general rule take photos with deeper DOF than larger format cameras all things otherwise equal.

Joe

 

[greybeard]

My 2 cents. DoF is really relative to the physical size of the aperture. If it is small enough you have a pin hole camera and don't really need any lenses at all and everything will be in focus. The bigger the opening, the shallower the DoF. When you start relating this opening to focal length and sensor size, things start getting confusing for a lot of people. This relationship between focal length and aperture opening is called FACTOR or F stop for short. If the focal length is 50mm and the aperture opening measures 25mm then the aperture is 50/25 or f2.0 but, if the focal length is 200mm and the aperture is 25mm then will be 200/25 or f8.0 But, a 200mm lens at f8.0 will have the same DoF as a 50mm at 2.0. because the aperture diameter will be the same. When you change sensor sizes DoF changes again because of the perspective (foreground to background size relationships) differential focal length has to do with sensor size. For instance a 50mm lens on FF will have the same perspective as a 35mm lens on a crop frame. Back in the day, they use to etch the DoF scale right on the lens next to the aperture ring. On my old FF 35mm I could set my lens to f11, put the infinity mark on (11) and I knew that everything would be in focus from 4ft to infinity would be in focus. Not quite so easy today.

 

[astroNikon]

Isn't bokeh that swirly stuff behind the subject?

If you want the *real* answer, watch this video

 

[petrochemist]

My 2 cents...

Except DOF is proportional to aperture & inversely proportional to focal length SQUARED. The focal length factor does not cancel out.

 

[Ysarex]

Back in the day, they use to etch the DoF scale right on the lens next to the aperture ring. On my old FF 35mm I could set my lens to f11, put the infinity mark on (11) and I knew that everything would be in focus from 4ft to infinity would be in focus. Not quite so easy today.

Today those DOF scales are inscribed on all Fuji X system non-zoom lenses -- nice feature.

Joe

 

[astroNikon]

^^^^
Now I'm gonna have to carry around a Fuji lens in my pocket for reference.

 

[robbins.photo]

^^^^
Now I'm gonna have to carry around a Fuji lens in my pocket for reference.

Don't forget a laser rangefinder to calculate your exact distance to the subject, as well as a super computer do do all this high end computational crap that is apparently required now for every shot.

Or you can do what I do and just turn the little command dial thingy to stop down the lens a bit more when you just know you need too without any calculus involved.

 

[Ysarex]

^^^^
Now I'm gonna have to carry around a Fuji lens in my pocket for reference.

Silly. They print paper tables for you.

Joe

 

[robbins.photo]

^^^^
Now I'm gonna have to carry around a Fuji lens in my pocket for reference.

Silly. They print paper tables for you.

Joe

Tables that once I gain enough experience to be able to use become more or less obsolete because I already have enough experience to know pretty much what I need without looking it up.

Handy. But hey, maybe in the future we can skip all this garbage and just post a link to the tables instead. BAM. Problem solved.