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09-23-2016, 12:40 PM   #1
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Quick question on MFD and the Max Magnification

I have a basic question about the close focusing capability of a full frame lens on my K-3. On the specification table of the lens review, it lists the Min Focus and the Max Magnification. Does the Minimum Focus Distance change when used with a crop sensor camera? I don't think it would, but then what happens to the Max Magnification? Does it remain the same even when the FOV of the FF camera and APS-C camera is different?
I am just trying to compare a DA lens and FA or DFA lenses. For example HD DA16-85mm Max Magnification is listed as 0.26x and HD DFA 28-105mm 0.22x. When both lenses are used with K-3, will DA16-85 give me a largest image of the subject I am taking? I am a little confused

09-23-2016, 12:46 PM   #2
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MFD and reproduction ratio are no different on crop or fullframe cameras. It is confusing, but the best way to think about crop and FF is just a different size canvas, nothing else. So if a FF gets you the insect head and antenna, but crop gets you just the antennae, when you make a pic out of just the antennae it seems more magnified, but actually it's not - you're just making a same size pic out of less which looks like more magnification. Sorry if this hasn't made things clearer - it's tricky to explain easily

Last edited by Nass; 09-24-2016 at 12:24 AM.
09-23-2016, 01:07 PM   #3
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Thank you for the quick reply So the Min Focus and Max Magnification numbers on the table is the same used with K-1 and K-3? I can compare FA and DFA lenses with the DA lenses without converting Max Magnification numbers? That is a relief. Thank you
09-23-2016, 01:20 PM   #4
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QuoteOriginally posted by taks Quote
On the specification table of the lens review, it lists the Min Focus and the Max Magnification. Does the Minimum Focus Distance change when used with a crop sensor camera? I don't think it would, but then what happens to the Max
No. The MFD is a lens property and cannot change regardless of what camera you put it on. Just like other lens properties. However, the FoV changes, which appears to increase focal length, and therefore magnification. So an APSC camera and FF camera with the same DFA 100mm mounted would produce slightly different looking photos of the same bug (subject). The bug would fill only part of the FF frame, but would fill almost all of the APSC frame. In that regard, the APSC photo would look like you got closer. The other thing is MP - APSC usually has higher pixel density, so the macro magnification ends up with more detail than the FF would have in the APSC area.
If you would print these two images, the APSC one would appear to be more magnified and have more detail on the bug. Of course, if you use APSC camera with low MP or FF camera with higher MP, this would change a little.

All in all, I would say not to worry about this at all. Take photos, get close, go macro, have fun. Upgrade to FF when you can clearly list the reasons why. Until then, the APSC gives you everything you want.


Last edited by Na Horuk; 09-23-2016 at 01:37 PM.
09-23-2016, 01:23 PM   #5
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Sorry, I don't have those actual tables so I can't guarantee if they've used the correct data. Sometimes manufacturers do get a little bit carried away with crop camera "equivalence" marketing rubbish. But the bottom line is that neither the reproduction ratio or the minimum focusing distance change, as properly defined.
09-23-2016, 01:36 PM   #6
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QuoteOriginally posted by taks Quote
I can compare FA and DFA lenses with the DA lenses without converting Max Magnification numbers?
Yes. The flange distance from the back of the lens to the sensor plane is the same for FF and APS-C cameras (I'm pretty sure). A 50mm lens on a FF camera is still a 50mm lens on a APS-C camera, which is why you set the SR focal length to whatever is engraved on the lens. The only difference between camera types is that since the APS-C sensor is smaller than FF, it doesn't capture as much of the scene. But the MFD and magnification at the sensor plane isn't affected. Take Nass' insect picture example. Say you make a 5" x 7" print of an insect taken with a full frame camera. Now get out your scissors and trim it down to 4" x 6". The size of the insect hasn't changed, but you won't have as much of it.
09-23-2016, 01:41 PM   #7
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Both Min Focus Distance and the Max Magnification are optical properties of the lens -- the sensor does not matter. Thus, you are right to pick the lens with the higher Max Magnification (assuming it's IQ at that magnification is good enough and you are happy with the focal length and working distance.)

But when the image is viewed fullscreen or printed, the total magnification -- which is the lens magnification multiplied by the magnification in the viewing or printing process -- will depend on the sensor.

A 4 inch wide rose bloom at 0.22X magnification will project a 0.88 inch (22mm) wide image on what ever sensor is back there. That's the optical magnification.

That 0.88 inch image will just about fill the width of a crop sensor but cover only 2/3rds of a full frame sensor. And, thus, the rose will appear more magnified in the final print from the crop sensor than in the print from a full frame sensor even if it was taken at the same magnification (just different sensors).

09-23-2016, 01:57 PM   #8
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Its less confusing thinking at the 1:1 ratio. The image shows actual size on the sensor. Think of setting a coin on the sensor and what is on the sensor is recorded. .25x would be like shrinking the coin to 1/4 size and setting it on the sensor.
09-23-2016, 02:32 PM   #9
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QuoteOriginally posted by Nass Quote
But the bottom line is that neither the reproduction ratio or the minimum focusing distance change, as properly defined.
And again...all together now...


Steve
09-23-2016, 05:11 PM   #10
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Original Poster
Thank you for all the replies I appreciate the help.
@Nass Thank you for your quick response and a follow up.
@ Na Horuk Yes K-3 is a great gear and it is giving me lots of enjoyment. I think I will stick with it for a while.
@Apet-Sure Great explanation. Thank you.
@photoptimist Thank you for the detailed explanation. It was very easy to follow and addressed my question very well.
@swanlefitte Thank you, that one I can visualize.
I wanted to compare the close focusing capabilities of the lenses looking at the lens review section. Now I see how the max magnification is the character of the lens itself and can be compared weather if it is a DA or DFA or other K mounts.
Good to be here in this forum Thanks
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