Focal Distance: furthest possible maintaining blurred BG

[rpt]

Exactly. Your eyes are being fooled. The blur is the same. That it doesn't look that way is an illusion. But...it's a good illusion.

I think that we need to define "background blur" now, because it does not look like the same COC at 200mm and 400mm.
And what about my extreme examples in the previous post? Do you still call it: "my eyes are fooled"?

If you crop just the tower from both images, and view them at the same size on the screen, they will look identical. That means the blur is identical.

Examples from http://toothwalker.org/optics/dof.html.

100mm f/4:

28mm f/4:

The car to the right of the subject has more blur with the 100mm lens than with the 28mm lens, right?

Wrong. Same blur. That's the case even in your extreme example.

I'm not saying it looks the same, the tower and car do look more blurred with the longer focal lengths. Like I said, it's good illusion.

Sorry, but it 404'ed...

Take the period out of the url and fire again.
http://toothwalker.org/optics/dof.html

 

[AprilForever]

Exactly. Your eyes are being fooled. The blur is the same. That it doesn't look that way is an illusion. But...it's a good illusion.

I think that we need to define "background blur" now, because it does not look like the same COC at 200mm and 400mm.
And what about my extreme examples in the previous post? Do you still call it: "my eyes are fooled"?

If you crop just the tower from both images, and view them at the same size on the screen, they will look identical. That means the blur is identical.

Examples from http://toothwalker.org/optics/dof.html.

100mm f/4:

28mm f/4:

The car to the right of the subject has more blur with the 100mm lens than with the 28mm lens, right?

Wrong. Same blur. That's the case even in your extreme example.

I'm not saying it looks the same, the tower and car do look more blurred with the longer focal lengths. Like I said, it's good illusion.

Sorry, but it 404'ed...

Take the period out of the url and fire again.
http://toothwalker.org/optics/dof.html

Thanks!

 

[Loswr]

Take the period out of the url and fire again.
http://toothwalker.org/optics/dof.html

Apologies. You can thank my iPhone's automatic punctuation...

 

[Pinchers of Peril]

Just use a lensbaby and have all the control in the world... allbeit slightly softer images

 

[yogi]

Im feeling dizzy and everything is getting blurry. Kidding aside, interesting subject & links. One thing you could do is use the lenses/cameras available to you and experiment on your own, unless you are trying to determine what lens you might be interested in buying to get the desired effect.

 

[RobT]

I thought about making a new topic for this question, but its very relevant to whats going on here.

Is compression based on focal length constant per lens or does it change based on sensor size?

For example, would an 85mm lens on a crop body visually maintain the same compression when put on a FF camera even though the focal length would appear shorter?

 

[dr croubie]

For example, would an 85mm lens on a crop body visually maintain the same compression when put on a FF camera even though the focal length would appear shorter?

a) If you take a head-shot photo with 85mm on aps-c, then swap the lens to an FF body and take the same photo from the same spot, you'll get a wider field of view and the head will be smaller within the frame. Then if you crop the second photo, you'll end up with *exactly* the same photo as the aps-c (except less MP).

b) If you take a head-shot photo with 85mm on aps-c, then swap the lens to an FF body and move closer so the head is the same size in the frame, then perspective will change and you'll get more 'wide-angle' or less 'compression' or whatever you want to call it.

 

[RobT]

Thank you!

That answers my question exactly.