Macro Reproduction Ratios on APSC.


coker

Link Posted 04/04/2016 - 21:53
I am aware of the rule, with full frame 35mm, that with a lens of x focal length, if x extension is applied, a repro. Ratio of 1:1 is achieved.

Does this still apply on APSC?

Thus, with my 100mm d fa macro, if I extend it by 100 mm, will I achieve 1:1 repro ratio?

......but I get that anyway.......albeit with/by focusing the lens......

Could someone please explain, put me right?

Thanks,

Roger.
The more I look, the more there is to see!

johnriley

Link Posted 04/04/2016 - 22:43
Common sense tells me that if we have 1:1 with 35mm format and we change the sensor behind the lens we crop the image. Therefore, the magnification increases.
Best regards, John

petrochemist

Link Posted 04/04/2016 - 22:57
johnriley wrote:
Common sense tells me that if we have 1:1 with 35mm format and we change the sensor behind the lens we crop the image. Therefore, the magnification increases.

Common sense tells you wrong then John.

Magnification here is size of image on the sensor / subject size. The rules for enlargement with extension apply whatever format is used. I've seen this relationship described in large format books, where a !:1 macro of a rose can include the whole flower...

The final image might be bigger but applying the crop factor is effectively the same as printing a larger image. It's this sort of reasoning that manufacturers use to put 'macro' on zoom lenses that only reach 1/4 life size or less on the sensor.
Mike
.
Pentax:K5ii, K7, K100D, DA18-55, DA10-17, DA55-300, DA50-200, F100-300, F50, DA35 AL, 4* M50, 2* M135, Helicoid extension, Tak 300 f4 (& 6 film bodies)
3rd Party: Bigmos (Sigma 150-500mm OS HSM),2* 28mm, 100mm macro, 28-200 zoom, 35-80 zoom, 80-200 zoom, 80-210 zoom, 300mm M42, 600 mirror, 1000-4000 scope, 50mm M42, enlarger lenses, Sony & micro 4/3 cameras with various PK mounts, Zenit E...
Far to many tele-converters, adapters, project parts & extension tubes etc.

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Last Edited by petrochemist on 04/04/2016 - 22:57

johnriley

Link Posted 04/04/2016 - 23:37
I'll have to think about that one! Just now it's too late and the theory was learned too long ago, so I'll go back and revise......
Best regards, John

Algernon

Link Posted 05/04/2016 - 08:53
coker wrote:
I am aware of the rule, with full frame 35mm, that with a lens of x focal length, if x extension is applied, a repro. Ratio of 1:1 is achieved.

Does this still apply on APSC?

Thus, with my 100mm d fa macro, if I extend it by 100 mm, will I achieve 1:1 repro ratio?

......but I get that anyway.......albeit with/by focusing the lens......

Could someone please explain, put me right?

Thanks,

Roger.

That's correct. With reproduction ratios sensor size is irrelevant.

At 1:1 the lens will be at 2F and the object will also be at 2F.

--
Half Man... Half Pentax ... Half Cucumber

Pentax K-1 + K-5 and some other stuff

Algi

Darkmunk

Link Posted 05/04/2016 - 10:12
What matters is the pixel pitch. If you cram more pixels into your sensor, it will display bigger and print bigger.
The 645z and K1 have the same pitch as the K5 (because that was the optimum ratio for quality), so a 25mm object will use the same number of pixels on all 3 formats. And the actual object will display the same size (the larger formats having more around the edge to crop off).
The K3, will create a bigger image because it crams more pixels into the same area.
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Algernon

Link Posted 05/04/2016 - 11:23
Darkmunk wrote:
What matters is the pixel pitch. If you cram more pixels into your sensor, it will display bigger and print bigger.
The 645z and K1 have the same pitch as the K5 (because that was the optimum ratio for quality), so a 25mm object will use the same number of pixels on all 3 formats. And the actual object will display the same size (the larger formats having more around the edge to crop off).
The K3, will create a bigger image because it crams more pixels into the same area.

Nothing to do with reproduction ratios. That's the same as saying 25ASA film will create a bigger image than 1600ASA film because it will stand up to a bigger enlargement.

If you had such a thing as a 23.7mm x 15.7mm slide to copy it 1:1 with an APS-C camera you would need 2x focal length in front of the camera. 4x focal length slide to sensor. Loss of light will always be 2 stops.

A little known fact with lenses is that you can't focus on an object closer than 1x focal length, so with the above 100mm lens it could be used for greater magnification than 1:1 between 100mm and 200mm in front of the lens centre.

--
Half Man... Half Pentax ... Half Cucumber

Pentax K-1 + K-5 and some other stuff

Algi

Darkmunk

Link Posted 05/04/2016 - 12:06
Quote:
Nothing to do with reproduction ratios. That's the same as saying 25ASA film will create a bigger image than 1600ASA film because it will stand up to a bigger enlargement.

That's nonsense for two reasons:
1- 25 ASA can be blown up bigger, precisely because of the finer grain.
2 - if you've got more pixels representing your 25mm, it will be bigger; this is simple maths.

And this is why my 645z can't produce a better picture of an ant than my K5
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Last Edited by Darkmunk on 05/04/2016 - 12:07

JAK

Link Posted 05/04/2016 - 18:07
It can't be bigger (both images are the same size on the film/sensor) it's just at a higher resolution.
John K
Last Edited by JAK on 05/04/2016 - 18:07

Darkmunk

Link Posted 05/04/2016 - 18:27
Higher resolution is bigger.
900 dots will print 3 inches, 1200 dots will print 4 inches.
Same with displaying on screen.
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Last Edited by Darkmunk on 05/04/2016 - 18:29

Algernon

Link Posted 05/04/2016 - 18:49
Your missing the point completely here. Macro reproduction ratios have nothing to do with how sharp the finished result is. Obviously a top Zeiss Macro lens will give better results than a cheap unbranded lens. The ratios are also used with microscopes.

You might find something of interest on this site.....

http://www.cambridgeincolour.com/tutorials/macro-lenses.htm

--
Half Man... Half Pentax ... Half Cucumber

Pentax K-1 + K-5 and some other stuff

Algi

Darkmunk

Link Posted 05/04/2016 - 20:48
Sharp??
Who said anything about sharp?
It's just maths; nothing to do with lenses. Why else would they keep increasing the pixel count on sensors?
But, as for sharpness, I found the K5iis sharper than the K3 even when interpolated up, and way better in the dark. So I sold the K3 and bought another K5.
Now.... back to the OP
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Algernon

Link Posted 05/04/2016 - 21:00
Ha! Ha! You shouldn't pixel peep especially when upscaling. You'll soon be convincing yourself that a $10 2X TC is better than the Pentax 1.4 TC just like this man did......

http://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/293399-pentax-h...

I'm waiting for the pixel peepers who will be saying shortly that a K-5 is better than the new FF K-1............ Who will be first

--
Half Man... Half Pentax ... Half Cucumber

Pentax K-1 + K-5 and some other stuff

Algi

JAK

Link Posted 05/04/2016 - 23:49
Darkmunk wrote:
Higher resolution is bigger.
900 dots will print 3 inches, 1200 dots will print 4 inches.
Same with displaying on screen.

You seem to be confusing enlarging an image with the field of view at the time of taking it. Yes, a higher pixel count on the sensor may yield an image that can be enlarged more, but I don't think that was the question originally being asked. The image at 1:1 on APS-C will have cropped content compared to that of a full frame image.
John K

Darkmunk

Link Posted 06/04/2016 - 08:41
Ha ha. oh dear. I know what the OP was talking about, that's why I steered the convo back that way.
If you have more pixels you can print larger. That's the bottom line.
However, an ant on a 645 sensor will take up the same number of pixels as an ant on a k5 (coincidentally - same pixel pitch more or less), so it will look tiny on the 645 if you print the whole picture without cropping.
The ant itself will look larger on the K3 than on the K5, at 100%, but it wil take up the same space in the frame. So if you zoom out to 12% the two images will look the same.

Nothing wrong with pixel peeping if you are looking for quality. You can try and use it as a derogatory term with others Algi, but it won't wash with me.
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