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11-01-2012, 05:37 PM   #16
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QuoteOriginally posted by Pentax Bob Quote
When using a macro lens designed for a full frame format on a Pentax DSLR, I know the effective focal length is multiplied by a factor of 1.5x. What is the impact on the image magnification? For example if the lens is set to a 1:1 ratio is it still 1:1 on the smaller sensor? If not, is the factor to multiply by 1.5X ? I am new to macro. Your help would be appreciated in determining what equipment to use.
To get the thread back on task, yes a 1:1 macro lens will be a 1:1 macro lens on both aps0c and 24x36 (135 film). For example, if I use the D FA 100 WR on my K-5 and my MZ-3 film body, it is capable of a maximum of 1:1 on both bodies. The same holds true for the Sigma 105mm EX DG macro, D FA 50/2.8 macro etc. However, the DA 35mm LTD macro would be a problem because it may not cover the film completely.

11-02-2012, 06:43 AM   #17
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In film you had 1:1 macro meant the same size on the film as the object was object and subject. IN digital, there is no film image to compare it to. There is no image left on your sensor. And the image that comes from the sensor is a different size depending on the pixel count. While I can see keeping the old system for classifying lenses , it makes no sense in terms of magnification. If you have a 50 mm lens on a 36x24 12 MP sensor and a 35mm lens on an APS-c 12 MP sensor, you get exactly the same amount of magnification from the two different size sensor and lens combinations. (If both cameras were 8 MP cameras.)

I'm saying this to illustrate a point, not to say it's true in the real world, I don't know of an FF camera with a pixel count low enough for this to actually be demonstrated. AT 12 MP the D700 has already exceeded the 8 to 10 MP practical limit to resolution of an APS-c lens. The superior LW/PH performance of DSLR lens/sensor means this would possibly only be true in a crop similar to the image above where the final print was cropped to APS-c size. So while the image size of a D700 may be less than that of a K-5, in terms of actual detail, the D700 might have more. The D700 is well under out resolving it's lenses while the K-5 would be well over, and is creating empty pixels, that are enlarging existing detail but not adding any new information.

But you might be able to favourably compare a D700 with a 50 to a K-x with a 35 to roughly illustrate the point, although I suspect at 12 MP the K-x is already our-resolving it's lens. But i would be close.

This stuff is so mundane I don't know why we waste time on it. Why is important to folks to say things like sensor pixel pitch doesn't affect the magnification of the system taken as a whole? It's so obviously and demonstrably wrong. Although I have to say.. at this point it's all moot. APS-c is past it's prime, in that the K-5 is already at the theoretical max for sensor/lens resolution, as is the D800. So at this point in time, film analogies apply completely, if you're talking about a K-5 and a D800 or even a D600. As APS-c cameras get to 16 MP and beyond, APS-c has no logical upgrade path other than FF. You've maxed out your lens resolution. It doesn't matter what you do to the sensor, you're just adding dead pixels, in that they don't capture any new detail.

If your K-5 isn't good enough for you now, it's probably not going to get any better, and there's absolutely no reason to stay with APS-c. On the other hand, if it's all you need now, there's still no reason to upgrade. You upgrade to fulfill LH/PH requirements, you need more definition in your output. As in prints somewhere north of 20 to 40 inches.
11-02-2012, 08:37 AM   #18
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This is crazy!

A 1:1 macro will produce an image with the same dimensions on the sensor as the subject in real life.

Given the same number of pixels per sensor, the same DPI output setting in each camera and the same viewing medium in DPI, the subject image size (which is the same as the size of the subject) on each of the respective sensors will stay the same, but the dimensions of the frame in the total image captured will shrink as you decrease the sensor size, so the relationship between these two changes, and the subject image will appear larger on the viewing media as the sensor size decreases. There is no magnification change.

It will take a 36mm subject to fill the frame horizontally with a 135mm frame, 24mm on an APS-C frame, 16mm on a 4/3 frame, and so on down the line of sensor formats. I've rounded the exact horizontal dimensions for this statement.

I'm not talking about image quality here, just the relation between the subject and the total frame captured.

Back to the OP's question which did not mention Image Quality -- With the same lens and at Minimum Focusing Distance, the subject image will appear 1.5x larger in relation to the frame captured on APS-C compared to one captured on 36x24 format. In other words, a 24mm subject will fill 2/3 (24/36) of the horizontal frame on 36x24, and fully fill the frame (24/24) horizontally on APS-C.

Add IQ into the equation, and things get difficult and very convoluted with far too many variables for most people to be able to get their heads around.

Scott
11-02-2012, 09:57 AM - 1 Like   #19
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Norm, a few points you seemed to have missed here


First of all, and lets go back to international standards, and a little common sense. Lenses have 4 fundamentally measurable attributes. Focal length, maximum aperture image circle, and minimum focusing distance. Focusing distance combined with focal length give you the maximum magnification. Nothing more nothing less.

Now when we print, yes, we can enlarge the image to any limit, which I have argues for a long time, renders all DOF calculators useless. Same for the rule of thumb to hand hold without blur because it is the total magnification of the image which ultimately results in a circle of confusion of 1/100 of an inch, which on a print is considered as a point.

Now you seem to think that film is infinite resolution, where as digital is fixed at one pixel, well, I hate to break it to you but regular 100 and 400 ISO film has about a grain size equal to 10MP. Since our cameras currently out resolve this, film is just as limited in enlargement as digital, if not more.

Second, even for an 8x10 print, where the CofC for digital is 20 microns, this is an image with a diameter of about 5 pixels, and the dot which is considered a point is about 16 pixels in total, not 1

That is where we are today with digital.

So lets not argue about where the split is between the image enlargement to sensor and the enlargement from sensor to print, since this latter is variable, there is no point discussing it. A lens maker cannot put a 1:1 magnification ratio on his lens just because you are going to enlarge the image more than someone else. The lens maker has no control over that so he marks his lens with known physical parameters he can measure

11-02-2012, 10:17 AM   #20
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QuoteOriginally posted by normhead Quote
In film you had 1:1 macro meant the same size on the film as the object was object and subject. IN digital, there is no film image to compare it to. There is no image left on your sensor. And the image that comes from the sensor is a different size depending on the pixel count. While I can see keeping the old system for classifying lenses , it makes no sense in terms of magnification. If you have a 50 mm lens on a 36x24 12 MP sensor and a 35mm lens on an APS-c 12 MP sensor, you get exactly the same amount of magnification from the two different size sensor and lens combinations. (If both cameras were 8 MP cameras.)

. . .
Actually, the the subject to image on the sensor at 1:1 with a D FA 100 WR on a K-5 sensor will in fact be 1:1 Norm. Also, a 50mm lens is a 50mm lens regardless of the film format or sensor format. That hold true whether it is a 135 film, 120 film, or any of the large format films. It also holds true for small digital sensors, 4/3 sensors, various aps-c sensors full frame sensors, mf sensors etc.
11-02-2012, 10:18 AM   #21
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QuoteOriginally posted by normhead Quote
This stuff is so mundane I don't know why we waste time on it. Why is important to folks to say things like sensor pixel pitch doesn't affect the magnification of the system taken as a whole? It's so obviously and demonstrably wrong. Although I have to say.. at this point it's all moot. APS-c is past it's prime, in that the K-5 is already at the theoretical max for sensor/lens resolution, as is the D800. So at this point in time, film analogies apply completely, if you're talking about a K-5 and a D800 or even a D600. As APS-c cameras get to 16 MP and beyond, APS-c has no logical upgrade path other than FF. You've maxed out your lens resolution. It doesn't matter what you do to the sensor, you're just adding dead pixels, in that they don't capture any new detail..
If you had a display/monitor with pixels the same size, number and density as the sensor the dimensions of the display would be the same size as the sensor. If you then displayed an image from this sensor at 100% the image would be the same size as the display. The image is larger on computer monitors or prints because the pixels are larger than the sensor.

If I took a picture of a metric ruler at 1:1 magnification (in the sense of macro photography) the distance between the 1mm markings would be 1mm. Viewed on the display described above at 100% magnification the distance of the 1mm marking of the image would be 1mm also.

I think the confusion is that in the film era magnification was used to describe the ratio between the size of the object and the size of the image on the film plane and enlargement factor was used to describe the ratio of the image size on the film or negative to the image projected on to paper or screen. Digital imaging refers to the ratio between the image pixels and the display pixels as magnification.

A contact print of an 8 x 10 inch negative on 8 x 10 inch paper would have an enlargement factor of 1 or 1x. If printed full frame at 16 x 20 inches it would have an enlargement factor of 2 or 2x. If I print part of the image on 4 x 5 inch paper in either case the enlargement factor would still be 1x or 2x respectively.

100% magnification on your computer display means one image pixel to one display pixel. The resulting image may be larger than can be displayed fully on your monitor. It's only larger than the original image on the sensor because the pixels on the monitor are that much bigger.

Yes enlargement and magnification are essentially the same thing but any specialized field develops its own specialized nomenclature which is subject to change with technology and popular usage. This nomenclature comes about to differentiate similar but different tasks or processes. Take the terms enlarging or blowing up an image - both are terms for making the resulting image larger. Your not likely to find these terms in digital photo editors - more likely it will be Zoom or Magnify.
11-02-2012, 10:37 AM   #22
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How about a practical example? Below are 2 photos taken with the pentax smc-f 50mm f2.8 macro, both at minimum focus.. The first is from my K-5 with a 1.5x crop factor aps-c sensor. The second is from a micro 4/3 camera with a 2x crop 4/3 sensor. They are still both 1:1 images though. When I think of explaining the difference, I think about visually projecting the sensor itself out from the camera and onto the subject - for both images, 1mm in the real world is accounted for as 1mm of the sensors width and/or height. The 4/3 image is for all intents and purposes a crop of the larger aps-c sensor due to both images being a 1:1 representation of the respective physical sensor sizes.




11-02-2012, 10:40 AM   #23
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QuoteOriginally posted by Not a Number Quote
Take the terms enlarging or blowing up an image - both are terms for making the resulting image larger. Your not likely to find these terms in digital photo editors - more likely it will be Zoom or Magnify.
Those terms are still there, with zoom/magnify you don't change the image data but with blowing up an image or enlargement you're changing a 12mp file to 24mp file for example with the help of interpolation.

11-02-2012, 10:42 AM   #24
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I believe Lowell has pretty much covered this, but:

Magnification: Property of the lens based on focal length and minimum focus distance. Is a set value.
Enlargement: What you do to the image file after you have captured it on a medium.

Magnification does not change just like how the focal length does not change. If you are saying how viewing a digital image at the 100% view on a 12MP vs a 24MP picture is different, that is a factor of enlargement.
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