Focus Breathing ..worth a check

Pistnbroke

Spurred on by the Megapixel thread I was testing my 28-300mm. In the end I put a ruler left right on a table and photographed it at 300mm . Width was 18 inches. I then did he same with my 300mm f4 prime ...width was 12 inches.
Now as far as I know primes don't breath so that means at 300mm and 10 ft my 300mm is 200mm !!!!

The implication is that if I change to another lens I don't need 300mm 200 will do ..mainly used for close ups of objects (flowers hands etc) at about 10 ft.

I wonder if the 24-120 breathes much as I never got on with that lens at 120mm?

heartyfisher

Did you test them at longer distances ? Just curious ...

A lense that has a range from 28-200 will probably focus breath almost as much ...
I think just about all super zooms focus breath ..its part of the design.. to get the "super" part of the super zoom...

Pistnbroke

Yes at 300mm and infinity both were the same field of view.
I also discovered the 24-105 sigma I was thinking of getting was only 80mm at short distances...good job did not spend on a 70-200 !!!

Ironheart

This was one of the major complaints of the 70-200 f/2.8G. At close distances it was more like a 150-160mm. This was fixed in the 70-200 f/2.8E, only $800 more than the G at $2800. Cinematic zoom lenses don't breathe, but are like $10,000 for a decent one.

Pistnbroke

This is a very good video on focus breathing.

The Nikon 70-200 goes down to 135mm at 7 ft and the Canon up to 230..!!!
Now for me who wants a close up going up is good ..( but canon is bad ) !!!
Oh what joy.

Paperman

I thought focus breathing was negligible, assuming it was less than 5% variation in focal length or so. We're talking about 50% here. Maybe that is why lens manufacturers never mention it or leave it out of their specs/tests ...

heartyfisher

Good video indeed.. !! nice find.

MegapixelSchnitzel

To fix that breathing in the 70-200E, how much sharpness was lost with the additional elements?

BVS

Well, the 70-200E is sharper than the G, as well as all other 70-200s, so I guess we'll never know how much was lost.

Anyway, I thought that was one of the reasons for moving the zoom ring, so they could move around the internals to fix the focus breathing.

Ironheart

@MegapixelSchnitzel that's a bit of a false dichotomy. There are prime lenses that have more elements than some zooms that are very sharp (Sigma Art). There are cinematic zooms that have no breathing, tons of elements, and are sharp as a tack.

https://www.bhphotovideo.com/c/product/857781-REG/Zeiss_1984_037_70_200mm_T2_9_Compact_Zoom.html

It has 22 elements/18 groups

The real trade-off is cost. Consumer zooms tend to breathe, because it is cheaper to make a lens that breathes while focusing than not.

The best way to address focus breathing is to make sure you are not changing the focal length when you focus. Some lenses clearly do this, as evidenced by the lens getting shorter and longer when you move the focus ring. Others are internal focus, but move a group of lenses that changes the focal length in order to focus. It usually requires a more complex movement of lenses and groups to maintain a steady focal length while adjusting focus.

The "trade-off" that the Nikkor 70-200 makes is that the focus and zoom rings were reversed in the G vs. the E. This is probably how they solved the breathing. The additional elements were used to flatten out the field, and spread more of the sharpness edge-to-edge, at least from the reviews I've read.

Just my thoughts anyway, I'm not a lens designer, nor do I play one on TV

Pistnbroke

I think this focus breathing should be tested for by DXO etc as its a big issue for me.I am normally about 10ft from a bride and to find my 300mm lens is only 200 is a problem . This will influence my choice of lenses in the future.

MegapixelSchnitzel

I used to think focus breathing was a shooting technique: don't inhale or exhale while focusing so you get a really sharp shot. And thanks for that explanation, Ironheart. Something about 22 elements in 18 groups makes me all tingly!

spraynpray

MegapixelSchnitzel said:

I used to think focus breathing was a shooting technique: don't inhale or exhale while focusing so you get a really sharp shot.

ROFL! That's a different kind of shooting MpS!