40-150 PRO focus breathing?

CrisPhoto wrote:

Anders W wrote:

CrisPhoto wrote:

...

Hi Christof,

Thanks for that. Quite an ambitious little exercise. Much appreciated.

Note, however, that the figures for the 75-300 are not right. This lens manages a focus distance of 0.9 meters only at 75 mm. At any other focal length, the minimum focus distance, is 1.5 meters. At 300 mm, which is where it manages a reproduction ratio of 0.18, its effective focal length is 194 mm, not 116 mm. And are you sure its MTF-values too are going down the drain at close distance? I haven't really tried to test it but ...

Hello Anders,

thanks for the hint, here the updated table. sorted by magnification "R":

Corrected table, real and measured specs

A couple of more things about the table now that I have had the time to digest it more carefully.

1. There is a similar issue with the 14-140 II as with the 75-300 (different minimum focus distance at different FLs). The 14-140 II manages 0.3 meters at 14-21 mm only. For the rest of the range, the minimum focus distance is 0.5 meters, in line with your findings in the penultimate column.

2. I can't get the reproduction ratios in the table to square fully with the FoV figures. I assume the FoVs are horizontal FoVs. If so a reproduction ratio of 0.30 corresponds to an FoV of 17.3 mm (the width of an MFT sensor) divided by 0.3, which is 57.67 mm rather than 60 mm. It seems like you have calculated with a sensor width of 18 mm instead of 17.3. With the correct sensor width, the figures in the "FoV" and "Real FoV" columns as well as those in the "Ratio" and "Real Ratio" columns (the latter of which need correction just like those in the "FoV" column), will be a bit closer to one another.

3. The focal lengths you calculated by means of the formula for a thin lens that I provided shouldn't be labeled "effective focal length". Although I understand why you label it like that, the term "effective focal length" is already occupied for slightly different purposes (see my reply to whumber here). What the formula I provided gives you is the focal length of a thin lens having the same reproduction ratio and linear FoV as the target lens when both are shot at the minimum focus distance of the target lens.

The 40-150 PRO lens has spoiled me, this little wonderful jewel works very reliable from macro close-up to tele. Made it very difficult for me to buy a walk around lens this year, hard to take a step back regarding IQ.

Although I have no personal experience with the 40-150/2.8 yet, I can certainly understand the feeling.

Here is a fast comparison of 40-150 PRO, Panasonic 14-140 II, Olympus 40-150 I and the PanaLeica 14-150:

I see what you are talking about. But I don't think the results from 14-140 II and 40-150/4-5.6 are all that shabby. And are you sure that the performance difference has much to do with the close focus? Wouldn't we see similar differences at other distances too?

This is the scene captured by the P 14-140 II, you can see the loss of detail and the weak color contrast even in this smallish screen shot

This a 100% crop of the scene above. (improved version with less dramatic difference, sorry, first version of this crop was not on the focus plane which was not on favor for the 10x zooms)

These were shot from a good tripod (I have a better one now), hand held the decrease of sharpness would have been even worse ...

Regards

Christof

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OM-D + Sam7.5, O25, O60, O75
O12-40, O40-150, P 14-140