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09-26-2020, 03:58 AM   #76
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QuoteOriginally posted by Serkevan Quote
0.5m is at 70mm. At 200mm the MFD is about 1m (same mag apparently).

The better example is the Pentax FA* 80-200/2.8. MFD of 1.4m, magnification of 0.19x.
But still, how much better is 0.2x than 0.13x? Does that mean that at 200mm and the minimum focus distance the Pentax is 140mm and the 150mm? I'm not good with maths, but it doesn't sound like a big difference to me.

09-26-2020, 05:16 AM   #77
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QuoteOriginally posted by Rondec Quote
But still, how much better is 0.2x than 0.13x? Does that mean that at 200mm and the minimum focus distance the Pentax is 140mm and the 150mm? I'm not good with maths, but it doesn't sound like a big difference to me.
The FA* is substantially "longer" (very airquoted) than the DFA* near minimum focus distance... I don't feel confident in putting a number to it because I'm not sure about the formula to estimate FL from magnification and MFD - and I don't think the behaviour affects performance THAT much anyway. If I were to take a wild guess and say the DFA* looks closer to a 135mm then the FA* should be above 150mm. But it's really something that wouldn't inform my purchase, I think.

In my experience, a tele is something that I use when I can't get closer to the subject - I don't typically need 200mm if I'm not at least 5-10 meters away from my subject. That's close enough to infinity that focus breathing is a non-issue. As an image is worth a thousand words, this is an example from my Tokina 70-210/4.5. It has internal zoom but not internal focus, and the MFD is 1.5m (which *is* long enough to be inconvenient sometimes, but not because of the magnification you get!). I took the photo at MFD and it was enough magnification for a fairly close-up detail... I normally wouldn't use a telezoom for such close subjects. Had I had the D FA 28-105 on the camera I would have used that one at 105 and gotten a tad closer!
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09-26-2020, 06:15 AM - 1 Like   #78
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QuoteOriginally posted by Rondec Quote
Is that true? I looked at the Z 70-200 f2.8 and it says it has a maximum magnification of 0.2x at 0.5 meters while the Pentax DFA *70-200 f2.8 has a maximum magnification of 0.13x and 1.2 meters. I'm no math wizard, but that doesn't feel very different. Maybe the focal lengths at 10 feet are dramatically different, but I think Nikon made a lot of noise about something that doesn't turn out to be that much different from past lenses.
There are some terms missing from the conversation. One is the field of view expressed in degrees. Until you have the numbers based on Field View, you don't know what you're talking about. Magnification is a good indicator, Field of View is the real deal.

The simple lens will alway present a consistent field of view across it's entire focus range. Any corrected or internal focus lens will alter the field of view as the point you focus on changes. What people are asking for in avoiding focus breathing is a corrected lens that emulates the performance of a simple lens.

All would be obvious, if manufacturers included the field of view at 10 feet, as well as infinity.

That being said, it was quite the shock after paying $1400 for my DA*60-250 to get so much less magnification shooting form approximately 10 feet, than I got with my Sigma 70-300. But as mentioned, the 1.4 TC got me back in the game. However, the DA*s images are so much higher res, it didn't take me long to get over it. To me it was an absolutely grievous source of outrage. These days it's not something I even think about. It comes down to "do you like the lens or don't you?," and I like the lens. So I happily put up with the focus breathing. You learn to work with the things you don't like to get what you want. If lenses that focus breath give me better IQ, I'll go with a lens that does focus breathing.

(Anticipate a response from someone who doesn't own a DA*60-250 telling me how good their copy of the Sigma 70-300 is. Every lens has it's champions.)
09-26-2020, 06:20 AM - 1 Like   #79
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QuoteOriginally posted by Serkevan Quote
The FA* is substantially "longer" (very airquoted) than the DFA* near minimum focus distance... I don't feel confident in putting a number to it because I'm not sure about the formula to estimate FL from magnification and MFD - and I don't think the behaviour affects performance THAT much anyway. If I were to take a wild guess and say the DFA* looks closer to a 135mm then the FA* should be above 150mm. But it's really something that wouldn't inform my purchase, I think.

In my experience, a tele is something that I use when I can't get closer to the subject - I don't typically need 200mm if I'm not at least 5-10 meters away from my subject. That's close enough to infinity that focus breathing is a non-issue. As an image is worth a thousand words, this is an example from my Tokina 70-210/4.5. It has internal zoom but not internal focus, and the MFD is 1.5m (which *is* long enough to be inconvenient sometimes, but not because of the magnification you get!). I took the photo at MFD and it was enough magnification for a fairly close-up detail... I normally wouldn't use a telezoom for such close subjects. Had I had the D FA 28-105 on the camera I would have used that one at 105 and gotten a tad closer!
Beholder3 had a chart where he compared the focal lengths of various lenses at minimum focus distances. They were surprisingly similar. The DFA *70-200 at minimum focus distance is 122mm the Z 70-200 f2.8 is 139mm. That's a real difference, but not as big maybe as some act on this thread.

HD Pentax-D FA 70-210mm f/4 ED SDM WR - Page 79 - PentaxForums.com

09-26-2020, 06:27 AM - 1 Like   #80
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QuoteOriginally posted by Serkevan Quote
In my experience, a tele is something that I use when I can't get closer to the subject - I don't typically need 200mm if I'm not at least 5-10 meters away from my subject.
What other options do you have?

K-3 and Tamron 300 2.8 and HD DA 1.4 TC (420mm) at approximately 3-5 meters.


If you don' have access to longer glass, you won't know what you might find it useful for.

Tamron 300 2.8 and F 1.7x AF Adapter


You don't know you might enjoy a head shot of a bird 4 meters away, until you can actually take the image.
09-26-2020, 06:35 AM   #81
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I agree with Norm. It's odd how we all talk about field of view and the equivalence between crop and full frame but we don't seem to talk about it with a single zoom lens on the same body and instead are using magnification. I honestly never think about magnification, even when shooting with a macro lens; I'm interested in the minimum focusing distance and the field of view that the lens provides. I'm sure there are many many times where a macro shooter would get interested in magnification but for me it's just not really entered my head. My 90mm Tamron can get down to 12 inches? Awesome, let's go find some flowers to shoot photos of. That's it. I don't really know why it would be different with a zoom, and without good examples, this is all a bit hard to relate to. I've seen examples via online video lens reviews which seems about the best short of experiencing it first hand.
09-26-2020, 07:02 AM   #82
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QuoteOriginally posted by normhead Quote
What other options do you have?

K-3 and Tamron 300 2.8 and HD DA 1.4 TC (420mm) at approximately 3-5 meters.


If you don' have access to longer glass, you won't know what you might find it useful for.

Tamron 300 2.8 and F 1.7x AF Adapter


You don't know you might enjoy a head shot of a bird 4 meters away, until you can actually take the image.
I have a 400mm Sigma, but it's always too long for my photography - I'm not really interested in birds in general, much less their headshots
Your images are great, of course.


On the topic of FOV, it would be much better if manufacturers added that, yeah... but they don't. You get the infinity FOV and that's kinda it, so magnification at a given MFD is the only indication we have :/

09-26-2020, 07:19 AM   #83
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guess I'm ready for more lashings:
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09-26-2020, 08:11 AM   #84
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QuoteOriginally posted by FozzFoster Quote
guess I'm ready for more lashings:
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Imagine how great that glass would be when shooting Portra 400 in your F6! In-lens stabilization AND less focus breathing!
09-26-2020, 08:48 AM   #85
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QuoteOriginally posted by FozzFoster Quote
guess I'm ready for more lashings:
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And, interestingly, the bottom one is a much better portrait
09-26-2020, 09:08 AM - 3 Likes   #86
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QuoteOriginally posted by Rondec Quote
But still, how much better is 0.2x than 0.13x? Does that mean that at 200mm and the minimum focus distance the Pentax is 140mm and the 150mm? I'm not good with maths, but it doesn't sound like a big difference to me.
I look at it from a practical viewpoint: 0.2x (1:5) magnification means I can fill the frame with a large butterfly, like an eastern tiger swallowtail. It also means that I can make an environmental portrait of a fairly large insect, such as a hummingbird both, with minimal cropping. 0.13x (1:7.7) would reduce the magnification of my subject by around a third.

Of course, we have so many pixels to play with these days that for most uses cropping doesn't pose much of a problem, but I still like to do as much with the camera and lens as I can.
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09-26-2020, 09:12 AM - 2 Likes   #87
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QuoteOriginally posted by Rondec Quote
But still, how much better is 0.2x than 0.13x? Does that mean that at 200mm and the minimum focus distance the Pentax is 140mm and the 150mm? I'm not good with maths, but it doesn't sound like a big difference to me.
It all is very basic trigonometry.

That is why comparing MFDs and max magnifications on a broad level doesnt even need any math, since I woudl expect it to be hugely obvious that by coming closer to the subject you can expect the image to get larger.


The Pentax A*200/4 macro looses 31% of the nominal 200mm at MFD.

The gold standard is the FA 77. But there it is quite easily to be seen that it is not internal focus.

The formula for effective focal length at MFD is (use same units for focal lnegths and MFD, e.g. mm or m):
focal length at MFD = MFD/(MaxMagnification+(1/MaxMagnification)+2)
09-26-2020, 09:14 AM   #88
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QuoteOriginally posted by Serkevan Quote
a much better portrait
QuoteOriginally posted by Serkevan Quote
interestingly
I find it more interesting that there is a clear difference and how ardently people will claim the difference is either not there or doesn't matter.
09-26-2020, 09:21 AM - 2 Likes   #89
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QuoteOriginally posted by FozzFoster Quote
I find it more interesting that there is a clear difference and how ardently people will claim the difference is either not there or doesn't matter.
The difference of these images is purely the difference in maximum magnification, which everyone can read from any spec sheet. The Pentax 70-210/4 would allow much more close up detail of the subject than either lens in the twitter post.

So thanks for the proof that basically nobody is after "focus breathing", but many are after maximum magnification.
09-26-2020, 09:25 AM   #90
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QuoteOriginally posted by beholder3 Quote
...but many are after maximum magnification.
This!
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