[Brightcolours]

Yeah I forgot about that Pentax.

 

So it is not true (all the Canons ever, all the Sonys on both platforms, both the new Nikkor f2.8 and the Nikkor f4, the Tokina f4, and all the other older models from Nikon, Pentax, Tamron and Sigma), and it is true (the outgoing Nikkor f2.8 VR II, the new Pentax, and the current Tamron and Sigma).

 

I count 2 current Canons (f4, f2.8), 3 Sony lenses (f2.8 A mount, f4 and f2.8 FE mount), 1 Nikkor lens (f4), 1 Tokina lens. that do not widen FOV towards MFD (that makes 7 lenses).

I count 1 Nikkor (f2.8 VR II), one Sigma, one Tamron and one Pentax that do widen FOV towards MFD (4 lenses).

 

So, mathematically it is less true than true

 

By the way, just to reiterate: All these lenses focus breathe (change FOV through the focus range).

It is just that some widen FOV towards MFD, and others narrow FOV towards MFD.

All a bother for video, but the narrowing is not a bother for photography.

[davidmanze]

  Well 7-4, OK, remove the F4 lenses, and it's a draw!!  not that it matters!..

   Actually I've always had a love for that Canon 70-200 F2.8, it's a beautifully constructed lovely looking and performing lens, I've never heard a word against it, quality Canon glass! 

 
 

  

  Funnily enough, I nearly went for a cheap  Nikor 80-200mm F2.8 push pull the other day with a bit of fungus for a hundred euros, with a view to cleaning it.....as it happened, I couldn't find any reference to whether it "focus breathed",   now I know!. ..

 

  Still I put the money towards the Sigma 150mm Macro, a good decission, it must have been a rare "flash" of lucidity that just happened to turn up at that moment, of course it disappeared just as quick as it came!

[obican]

By the way, just to reiterate: All these lenses focus breathe (change FOV through the focus range).

It is just that some widen FOV towards MFD, and others narrow FOV towards MFD.

All a bother for video, but the narrowing is not a bother for photography.

 

Btw, Minolta Beercan is one of those who narrow its FOV towards MFD. I think it's around 100mm or so focused up close, which can be quite a problem sometimes.

[Brightcolours]

Btw, Minolta Beercan is one of those who narrow its FOV towards MFD. I think it's around 100mm or so focused up close, which can be quite a problem sometimes.

Ok,what do you mean exactly? 70mm at infinity to 100mm at MFD?

 

Do you realize that when one does not change focal length, FOV always will narrow towards MFD?

[obican]

Ok,what do you mean exactly? 70mm at infinity to 100mm at MFD?

 

Do you realize that when one does not change focal length, FOV always will narrow towards MFD?

 

Actually, here you go

 



 

Screen capture I had made from LR some while ago. On the left is a Sigma 17-70 at 70mm. On the right is the Beercan at 70mm. Shot from the same spot, quite close to the minimum focus distance. Beercan image EXIF is being tagged at 75mm at the wide end btw, even though it's sold as a 70-210mm lens. 

 

Also, FOV will not always be narrower towards MFD. Nikon's old 70-200/2.8 that is being discussed here gets significantly wider at MFD. Even  you said so:

 

By the way, just to reiterate: All these lenses focus breathe (change FOV through the focus range).

It is just that some widen FOV towards MFD, and others narrow FOV towards MFD.

All a bother for video, but the narrowing is not a bother for photography.

[Brightcolours]

Actually, here you go

 



 

Screen capture I had made from LR some while ago. On the left is a Sigma 17-70 at 70mm. On the right is the Beercan at 70mm. Shot from the same spot, quite close to the minimum focus distance. Beercan image EXIF is being tagged at 75mm at the wide end btw, even though it's sold as a 70-210mm lens. 

 

Also, FOV will not always be narrower towards MFD. Nikon's old 70-200/2.8 that is being discussed here gets significantly wider at MFD. Even  you said so:

Read what I wrote  :

"Do you realize that when one does not change focal length, FOV always will narrow towards MFD?"

 

With "one" I meant a lens. So when one lens does not change focal length. So, if the focal length DOES NOT CHANGE. This then means that the focal length of that Nikkor VR II does indeed change a lot, it gets a lot shorter. 

If it would only get a little shorter or would not change, FOV would narrow towards MFD.

 

Is it clear to you now?  B) 

 

Not sure what above image is supposed to show. I do know that with the Sigma 18-50mm f2.8 EX DG I had it shortened focal length towards MFD to such an extent that you saw the FOV get more wide towards MFD. My guess is that the Sigma 17-70mm does the same (look through the view finder when going through the focus range, and it will be clear immediately).

 

To make things more graphic:

[ATTACHMENT NOT FOUND]

 

On top you see the FOV change towards MFD of my Canon EF 70-200mm f4 L USM at 200mm setting. You see it get more narrow at MFD compared to infinity. This means that its focal length loss is quite minor.

On the bottom my then Sigma 18-50mm EX DG at 50mm. You see a very severe FOV widening towards MFD, which means a quite severe focal length loss.

 

You see what my guess is now, about your 17-70mm?

[wim]

I did some calculatiosn a few years ago, with a known focusing distance, known object width, and known size on the sensor of the object.

This way you can calculate everything necessary to figure out true FL.

 

For the Nikon 70-200 F/2.8 VR, I think the VR1, forgot to write that down, I found the following:

 

1. focused at 373.0 inch, 9.47 m, the calculated FL was 194 mm (193.5) - that is within tolerance (say +/- 5%).

2. focused at 178.0 inch, 4.52 m, the calculated FL was 192 mm (192.4) - still within tolerance.

3. focused at 44.6 inch, 1.13 m, the calculated FL was 169 mm (168.8) - way out of tolerance, and very visible.

 

This is one of the reasons why I do not like IF-mechanisms, as they generally do show this type of focus breathing. Macro lenses with IF are generally very good examples of this behaviour, and often easy to calculate, based on MFD and magnification factor.

The Canon EF 100 F/2.8 USM macro at MFD is only 70 mm, the EF-S 60 F/2.8 macro is 50 mm, and the EF 180L at MFD is something in the order of 120 mm, if not less.

 

Generally speaking, Canon's L-zooms are actually very good in this regard, none to very little focus breathing, last I checked anyway.

 

Kind regards, Wim

[Brightcolours]

;Any lens which does not change focal length through the focus range does show focus breathing, Wim. They narrow the FOV.

There are two "types" of focal breathing: The lens can narrow the FOV and the lens can winden the FOV. In my above image example, you see two IF lenses. One widens, one narrows.

 

To calculate FL correctly, one needs to know the nodal points. How did you figure those out?

[wim]

;Any lens which does not change focal length through the focus range does show focus breathing, Wim. They narrow the FOV.

There are two "types" of focal breathing: The lens can narrow the FOV and the lens can winden the FOV. In my above image example, you see two IF lenses. One widens, one narrows.

 

To calculate FL correctly, one needs to know the nodal points. How did you figure those out?

 

You don't necessarily need to know the nodal points, as long as you know focusing distance, size of object, size of object in the image, maximum image size and therefore magnification anf FoV. I guess you could calculate the nodal points based on those, but I was just trying to figure out the effective FL

 

Kind regards, Wim

[BasilG]

No one in their right mind is going to put an extension tube on the 70-200 to shoot at MFD. Next you are probably going to tell me that you have the whole rig on a heavy tripod running around after these critters? Didn't someone tell you that Nikon invented a macro lens decades ago?

 

I used to shoot macro using a 400 mm lens and tubes. Was great for insects. Great working distance, excellent subject isolation. You may be unfamiliar with this way of shooting close-ups, but that doesn't mean it's no good. In fact it's probably the best way for some subjects.