minimum focus distance

[Mark L]

A resent quote from John elsewhere on AP,
"One thing to keep in mind is that "minimum focus distance" is the distance from the sensor, not the distance from the front of the lens. I somehow never understood this, until ...."

I have just bought a lens that is about 24cms long. Am a little inclined to check this out, but for the subject matter I take photos of a step back probably works.;)

Kinda posting this for others to learn from any comments.;)

[ameerat42]

I don't understand. Can you cite his post?

[Mark L]

I don't understand.



"One thing to keep in mind is that "minimum focus distance" is the distance from the sensor, not the distance from the front of the lens.
That's the important bit.
Edit my post though.

[ameerat42]

OK, now I see. Somehow I only saw a pair of quotes before.

And I thought it was from the nodal point/position/plane of the lens.
(So you're "boaf" wrong:D - if I'm right:confused013)

[arthurking83]

Yeah, some lenses can be downright painful with their MFD figures.

The really older versions of the Tammy 90/2.8(great lens tho! :th3:) have a very short MFD, and as the front lens element is deeply recessed, it makes the lens basically touch the subject.

This thread is a timely reminder for folks to also brush up on where their sensor plane is on their camera too.
This is the place where MFD is measured too. On the camera body(usually on the top plate) is a circle with a line drawn through it.

It'll look something like ... ϴ ...(that), but the line extends past the circle.
The line itself is where the sensor plane is.

Some lenses(Nikon's 105VR Micro) can focus just a bit closer than it's stated MFD! :confused013

For 'most situations' with 'most normal' lenses, MFD is too far/long to be anything to really concern with. But when you get down to true macro magnifications, it helps to know more about it.

Some lenses I've noticed may also quote 'working distance' .... WD (I think Zeiss does ?? .. can't remember .. maybe Leica ??).
This is the distance from the subject to the front lens element

[MissionMan]

I hadn't really noticed this until I got my 20mm and suddenly found the focal distance from the lens itself is about 10cm from the front of the lens. I think it's a lot more noticeable because of the wide angle of the lens.

[arthurking83]

I hadn't really noticed this until I got my 20mm and suddenly found the focal distance from the lens itself is about 10cm from the front of the lens. I think it's a lot more noticeable because of the wide angle of the lens.

I reckon that it's more noticeable because that lens so large, compared to some of their earlier models.

ie. if you look at the specs of the old screw driven 20/2.8 AF-D lens, it's length is only 42.5mm but the 20/1.8 AF-S is 80.5mm in length. That's basically doubled! But more importantly it's 38mm longer.
The AF-D lens has a 25cm MFD, and Nikon's modernisation of the AF-S model has shortened that by 5cm to 20cm now.

But if you used the two lenses at MFD, on the AF-S model, as you said, it's basically 10cm from the front of the lens .. but using the older AF-D lens, the subject to lens distance will be 4cm further away by comparison.

You're still using the same focal length(ie. wide angle), but the size of the lens is what makes it a bit freaky feeling. Take into account that the lens diameter of the AF-S lens is much wider too(77mm filter vs 62mm filter for the AF-D) .. and the subject gets swamped by the much larger sized AF-S lens(compared to similar focusing with the older AF-D len)