Focal Distance: furthest possible maintaining blurred BG

[neuroanatomist]

I meant the same framing, of course.
My opinion was determined by looking on my photos, thus your simplified theories are not able to reverse my mind.

Obviously. Misinformed opinion trumps fact every day of the week, in one's own mind if not in the real world.

Through the filter of our own misconceptions, everyone else's statements are part of the blurry background.

Well said Sir.

Why, thank you!  You were, of course, quite correct.  Don Quixote notwithstanding, the windmill will remain in this case. I'm out.

[PackLight]

I meant the same framing, of course.
My opinion was determined by looking on my photos, thus your simplified theories are not able to reverse my mind.

Obviously. Misinformed opinion trumps fact every day of the week, in one's own mind if not in the real world.

Through the filter of our own misconceptions, everyone else's statements are part of the blurry background.

Well said Sir.

Why, thank you!  You were, of course, quite correct.  Don Quixote notwithstanding, the windmill will remain in this case. I'm out.

Amazingly the entire thread was blurry from the start. Unless the OP had provided some definition of what "isolate" meant. We can discuss at what point equal lenses have equal DOF and similar Blur but unless you can define at what point an item reaches "isolation" it is all meaningless.

Using the common definition of isolate which means "alone" one could say in the picture with the tower that was used as an example the original subject could have not been considered "isolated" as it was still apparent in the background.

[risc32]

When i started reading the thread i wasn't understanding the OP. I figured it perhaps just over my head, but the terminology seemed a bit funny. Then i got a better understanding of what he was asking and promptly agreed with neuroanatomist and his side. This might be a hard thing for some to get their head around.

[PackLight]

When i started reading the thread i wasn't understanding the OP. I figured it perhaps just over my head, but the terminology seemed a bit funny. Then i got a better understanding of what he was asking and promptly agreed with neuroanatomist and his side. This might be a hard thing for some to get their head around.

Yes Kudos to Neuro for answering an otherwise vague question.

I don't think it is a hard thing for someone to get their "head" around, as much as it is a scenario that would very seldom come in to play. In very few instances would the comparison of two lenses come up like this. I have heard this discussion on a forum at least one other time. But since you have a different FOV for your background you will never be comparing identical pictures. Usually a person thinks about proper framing first.

I suppose if you were big time and had a shoot coming up, knew the location you were going to and what type of bokeh you were shooting for it would help in determining which lenses to take along. Personally I don't have that problem, all my lenses fit in a few bags I just throw them all in and go. Neuro might have a little more difficulty and have to think about how much of his kit to take along.

[bycostello]

biggest focal length as close as you can be to the subject

[PeterJ]

biggest focal length as close as you can be to the subject

Probably an MP-E 65 then, or would the 180mm be better?

[SwissBear]

Well, my question was quite blurry - that might be due to the fact that i'm neither native speaker nor have a vast vocab in this rather specific section of technical english.

But "to get better with my english", what could be a better wording for it?

Thank you again for all the answers. as it seems, this topic isnt quite easily understood

[PackLight]

Well, my question was quite blurry - that might be due to the fact that i'm neither native speaker nor have a vast vocab in this rather specific section of technical english.

Could be,

But the answer was for a specific lens, after your clarifications it would be this one;

http://www.lensrentals.com/rent/canon/lenses/normal-range/canon-50mm-f1.0l

[moocowe]

I'm probably way off here, but could the TS-E 90mm be a viable alternative to the 85mm f/1.2 for subject isolation since it is closer focusing and can be tilted for selective focus?

I notice the original post says "without tilting", but I'm curious.

[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...

[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!

[neuroanatomist]

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.