40-150 PRO focus breathing?

Today my Olympus 40-150 PRO lens arrived and while it does feel like a great lens, there's something that I noticed. I was comparing it against my trusty old Minolta Beercan and I was noticing that the Olympus zoomed all the way in at 150mm was producing a similar result as the Beercan at 210mm.

I ran the test again, but this time with APS-C crop mode turned on my Sony cam to simulate ~300ishmm and I had to get significantly closer to my test subject (in this case a old Charmander piggy bank) with the Oly to produce a similar FOV. This isn't a deal-breaking issue for me but it wasn't something I was expecting to see as I hadn't seen any reports of focus breathing issues with this lens.

Is this something that is known about this lens? Is mine the special one on the block? Or am I just fundamentally misunderstanding equivalency here? Like I said, not a huge deal-breaker but was definitely interesting to see.

Just ran the test again on a Andrew Jackson bobble head (don't ask why I own such weird things) and I'm adding a picture to demo what I'm talking about. Both shots were taken from the same distance away, which was roughly ~3 1/2 feet. The Sony was on crop mode but it isn't represented in the data shown.

Oly on the left at 150mm and the Minolta on the right at 210+APS-C crop mode

Did you use Clear Image Zoom on the Sony?

I used the APS-C crop mode on my a7S, which simply crop's in 1.5 to Sony's APS-C sensor size. Essentially turning it from a 12 mp FF to a ~5 mp APS-C.

Almost all lenses with Internal Focus designs have focus breathing issues - just a matter of how much.

You will need to buy a parfocal lens design to avoid focus breathing. Those are high priced optics - usually only found in cinema lenses.

The focus breathing issue was mentioned in a review of Jan of 2015

http://www.photographyblog.com/reviews/olympus_m_zuiko_digital_ed_40_150mm_f_2_8_pro_review/

I used the APS-C crop mode on my a7S, which simply crop's in 1.5 to Sony's APS-C sensor size.

Yes, you had made that clear. But I've never heard of focus breathing changing a lens' angle of view by some 50% as appears to be the case here. So, I wondered if there might be another explanation -- such as you inadvertently using digital zoom on your Sony, in addition to crop mode (if that's possible at all). Anyway, I'll take your reply as a  'No'.

Sorry about that. I was typing on my phone and that tends to make me grouchy and just generally a annoying person. Not a good excuse but its all I got.

Anyways, yes that would be a 'no'.

SVPhotography wrote:

Almost all lenses with Internal Focus designs have focus breathing issues - just a matter of how much.

You will need to buy a parfocal lens design to avoid focus breathing. Those are high priced optics - usually only found in cinema lenses.

The focus breathing issue was mentioned in a review of Jan of 2015

http://www.photographyblog.com/reviews/olympus_m_zuiko_digital_ed_40_150mm_f_2_8_pro_review/

Ah, that would be why I didn't see much mention of it. I tend to not seek out his reviews that often. They're a bit too clinical for my tastes. Goes to show I should read his blog more!

Thanks for pointing that bit out though!

And to clarify, I was more asking if that much focus breathing was normal for the lens, not so much if focus breathing happened at all. Sorry that I wasn't clearer on that.

Guy Parsons wrote:

SVPhotography wrote:

Almost all lenses with Internal Focus designs have focus breathing issues - just a matter of how much.

You will need to buy a parfocal lens design to avoid focus breathing. Those are high priced optics - usually only found in cinema lenses.

The focus breathing issue was mentioned in a review of Jan of 2015

http://www.photographyblog.com/reviews/olympus_m_zuiko_digital_ed_40_150mm_f_2_8_pro_review/

For me the term "focus breathing" is totally wrong.

The effect really is "focal length breathing" if "breathing" is needed in the expression.

Simply a matter of the focal length changing as the lens is focussed closer, it happens to varying degrees with internal focus designs.

I first met the effect in film days with the Nikon 105/2.8 macro lens where it is an effective 79mm lens when focused to 1:1 ratio macro.

So, it is best to do angle of view and comparative framing tests with the lens focused at infinity.

Regards...... Guy

I was definitely going to do further testing on it when I had time. I had just noticed the breathing when I was toying around with the lens pretty much 5 minutes after the UPS truck dropped it off.

Figured I'd ask here about it before I drove myself up the wall wondering if there was anything wrong (I have a tendency to get defective equipment). Good to know its just the lens doing its thing.

I compared the 40-150/2.8 to the PL 14-150/3.5-5.6, P 14-140 II, the O40-150/4-5.6 and the O14-150/4-5.6.

From all these lenses, the 40-150/2.8 was the best one which means also it will have the best macro magnification factor. Even better, it is by far the sharpest of all, the other lenses degrade quite dramatically at short distances. Especially the Oly 14-150.

The other mFT lenses were slightly worse and the old Leica Elmar 14-150 was very much worse. For short distances it has the same FOV as the 40-150 at 110mm. This is very sad because the old PLeica has a nice short focus distance which could have been good for close up.

I don't think the 40-150 PRO is bad, just the opposite. Maybe you can check the test setup (did you measure the distance from front element to subject or from camera back)?

Christof

I know that Parfocal (vs varifocal) lenses do not change focus with change in focal length (zooming) but I was not aware that the design features of those lenses (mostly expensive video lenses) would affect focus breathing one way or the other.

I find very little focus breathing with my copy of the 40-150 Pro. Maybe the issue is that the focal length of the beercan is getting longer as you focus closer, like the Canon 70-200ii?

Arctra wrote:

Today my Olympus 40-150 PRO lens arrived and while it does feel like a great lens, there's something that I noticed. I was comparing it against my trusty old Minolta Beercan and I was noticing that the Olympus zoomed all the way in at 150mm was producing a similar result as the Beercan at 210mm.

I ran the test again, but this time with APS-C crop mode turned on my Sony cam to simulate ~300ishmm and I had to get significantly closer to my test subject (in this case a old Charmander piggy bank) with the Oly to produce a similar FOV. This isn't a deal-breaking issue for me but it wasn't something I was expecting to see as I hadn't seen any reports of focus breathing issues with this lens.

Is this something that is known about this lens? Is mine the special one on the block? Or am I just fundamentally misunderstanding equivalency here? Like I said, not a huge deal-breaker but was definitely interesting to see.

It's very easy to calculate the focus breathing from the lens specs. The 40-150 PRO has a max reproduction ratio of 0.21 (at 150 mm obviously) and a minimum focus distance of 0.7 meters. The focal length, F, at that reproduction ratio, R, and focus distance, D, is calculated as

F = D/(1/R + R + 2) = 700/(1/0.21 + 0.21 + 2) = 100 mm

so yes, certainly some focus breathing going on, just as one might expect.

Anders W wrote:

Arctra wrote:

Today my Olympus 40-150 PRO lens arrived and while it does feel like a great lens, there's something that I noticed. I was comparing it against my trusty old Minolta Beercan and I was noticing that the Olympus zoomed all the way in at 150mm was producing a similar result as the Beercan at 210mm.

I ran the test again, but this time with APS-C crop mode turned on my Sony cam to simulate ~300ishmm and I had to get significantly closer to my test subject (in this case a old Charmander piggy bank) with the Oly to produce a similar FOV. This isn't a deal-breaking issue for me but it wasn't something I was expecting to see as I hadn't seen any reports of focus breathing issues with this lens.

Is this something that is known about this lens? Is mine the special one on the block? Or am I just fundamentally misunderstanding equivalency here? Like I said, not a huge deal-breaker but was definitely interesting to see.

It's very easy to calculate the focus breathing from the lens specs. The 40-150 PRO has a max reproduction ratio of 0.21 (at 150 mm obviously) and a minimum focus distance of 0.7 meters. The focal length, F, at that reproduction ratio, R, and focus distance, D, is calculated as

F = D/(1/R + R + 2) = 700/(1/0.21 + 0.21 + 2) = 100 mm

so yes, certainly some focus breathing going on, just as one might expect.

This equation is based on a thin lens model and while it may be fairly accurate at infinity focus, it's going to fall apart at close focus distances with thick lenses (i.e. any real lens you can imagine), especially for a lens where the distance between the principal planes is on the order of 10% of the subject distance.

whumber wrote:

Anders W wrote:

Arctra wrote:

Today my Olympus 40-150 PRO lens arrived and while it does feel like a great lens, there's something that I noticed. I was comparing it against my trusty old Minolta Beercan and I was noticing that the Olympus zoomed all the way in at 150mm was producing a similar result as the Beercan at 210mm.

I ran the test again, but this time with APS-C crop mode turned on my Sony cam to simulate ~300ishmm and I had to get significantly closer to my test subject (in this case a old Charmander piggy bank) with the Oly to produce a similar FOV. This isn't a deal-breaking issue for me but it wasn't something I was expecting to see as I hadn't seen any reports of focus breathing issues with this lens.

Is this something that is known about this lens? Is mine the special one on the block? Or am I just fundamentally misunderstanding equivalency here? Like I said, not a huge deal-breaker but was definitely interesting to see.

It's very easy to calculate the focus breathing from the lens specs. The 40-150 PRO has a max reproduction ratio of 0.21 (at 150 mm obviously) and a minimum focus distance of 0.7 meters. The focal length, F, at that reproduction ratio, R, and focus distance, D, is calculated as

F = D/(1/R + R + 2) = 700/(1/0.21 + 0.21 + 2) = 100 mm

so yes, certainly some focus breathing going on, just as one might expect.

This equation is based on a thin lens model and while it may be fairly accurate at infinity focus, it's going to fall apart at close focus distances with thick lenses (i.e. any real lens you can imagine), especially for a lens where the distance between the principal planes is on the order of 10% of the subject distance.

I am well aware that it is based on a thin lens model but that doesn't make it useless for the purpose at hand. Moreover, the formula is useful precisely at close focus distances. At infinity, there is no real need for it.

What the results of the formula tells us is that the focal length of the 40-150 when set to 150 mm and shot at its minimum focus distance is equivalent to that of a thin lens (a single lens element) with a focal length of 100 mm. If there were no focus breathing, it would instead be equivalent to a thin lens with a focal length of 150 mm (provided that the 150 mm specification is correct in the first place).

Anders W wrote:

whumber wrote:

Anders W wrote:

Arctra wrote:

Today my Olympus 40-150 PRO lens arrived and while it does feel like a great lens, there's something that I noticed. I was comparing it against my trusty old Minolta Beercan and I was noticing that the Olympus zoomed all the way in at 150mm was producing a similar result as the Beercan at 210mm.

I ran the test again, but this time with APS-C crop mode turned on my Sony cam to simulate ~300ishmm and I had to get significantly closer to my test subject (in this case a old Charmander piggy bank) with the Oly to produce a similar FOV. This isn't a deal-breaking issue for me but it wasn't something I was expecting to see as I hadn't seen any reports of focus breathing issues with this lens.

Is this something that is known about this lens? Is mine the special one on the block? Or am I just fundamentally misunderstanding equivalency here? Like I said, not a huge deal-breaker but was definitely interesting to see.

It's very easy to calculate the focus breathing from the lens specs. The 40-150 PRO has a max reproduction ratio of 0.21 (at 150 mm obviously) and a minimum focus distance of 0.7 meters. The focal length, F, at that reproduction ratio, R, and focus distance, D, is calculated as

F = D/(1/R + R + 2) = 700/(1/0.21 + 0.21 + 2) = 100 mm

so yes, certainly some focus breathing going on, just as one might expect.

This equation is based on a thin lens model and while it may be fairly accurate at infinity focus, it's going to fall apart at close focus distances with thick lenses (i.e. any real lens you can imagine), especially for a lens where the distance between the principal planes is on the order of 10% of the subject distance.

I am well aware that it is based on a thin lens model but that doesn't make it useless for the purpose at hand. Moreover, the formula is useful precisely at close focus distances. At infinity, there is no real need for it.

I think that tells you a lot about the usefulness of that equation for your intended purpose. For some lenses that have principle planes relatively close together and have a long MFD, the equation may be somewhat useful, but for a lens like the 40-150 it completely falls apart. If you want another example where your formula is not useful, look at the Canon 70-200ii. The thin lens approximation equation would suggest that the focal length at MFD decreases to somewhere around 176mm, while direct measurements show that the focal length actual increases to well above 200mm at MFD.

What the results of the formula tells us is that the focal length of the 40-150 when set to 150 mm and shot at its minimum focus distance is equivalent to that of a thin lens (a single lens element) with a focal length of 100 mm. If there were no focus breathing, it would instead be equivalent to a thin lens with a focal length of 150 mm (provided that the 150 mm specification is correct in the first place).

I'm sorry but you're just flat out wrong on this one. The focal length of the 40-150 is nowhere close to 100mm at MFD when set to 150mm. In fact, there's almost no change in focal length at 150mm between infinity and MFD. Below are shots of a test target taken with the 40-150 @ 150mm with the focus set to infinity and MFD. If the thin lens approximation was reasonable, we would see a siginificant decrease in the target size. Instead what we see is almost zero change in the target size, at least to within the precision that the out of focus target will allow us.

Infinity Focus | f/22 | Subject Distance ~8ft

MFD Focus | f/22 | Subject Distance ~8ft

Fri13 wrote:

CrisPhoto wrote:

(did you measure the distance from front element to subject or from camera back)?

The metering point is always from the sensor plane, that is marked with circle that is divided by a line and usually placed on the side of EVF hump or top plate. Like example with E-M1 it is on left side of the hot shoe.

So when you are doing accurate focusing ie. macro photoraphy etc, you place your metering tape on that and meter distance to the subject from it.

Yes, I know the official part.

But if I would compare the 40-150 close-up capabilities to lets say the 60mm macro I would get completely different perspective/magnification because the nodal point or the front lens of the 40-150 is much nearer to the subject. This is independent from the sensor plane.

If the OP compared a very long FF lens with the smaller 40-150 (or a compact FF macro prime with the taller 40-150 zoom) it would also yield very different results when the camera/tripod stays at the same distance.

Christof