Question for the Technical Gurus

[Manfred M]

Paul: I wouldn't use the online calculator you found because the Nikon cameras to choose from were discontinued so long ago that neither of my cameras, which have also been discontinued, are on the list

Just choose a more current camera with the same sensor size. Sensor size is all that really matters when using this calculator, and Nikon has not changed the size of either their APS-C or full-frame sensors.

[george013]

The standard equations aren't accurate with macro lenses because the nominal focal length is incorrect. You will generally obtain higher magnification than the equation gives you. You can find an interested experiment and explanation from "Lord V"--Brian Valentine, a superb macro photographer--here.

I think there's some miscalculation in your link.

My 105mm ex lens with 65mm of tubes, should have a magnification factor of (105+65)/105= 1.62:1.
It actually gives 1.97:1
Someone else supplied the figures for their canon 100mm macro lens- this with 68mm of tubes should give (100+68)/100 = 1.68:1
but actually gives 2.14:1.

Look at the link of Paul and my former post. In that link 2 situations are calculated: one with the lens turned in completely and one with the lens turned out completely.
In the quote above from your link the nominal focal length is used together with a magnification of 1. He should use the image distance which is the focal length + the internal lens extension. Beside that I don't believe the formula he's using is correct. I hope he's a better macro photographer as a macro calculator.

George

[pnodrog]

Paul: I wouldn't use the online calculator you found because the Nikon cameras to choose from were discontinued so long ago that neither of my cameras, which have also been discontinued, are on the list.

For anyone interested in the online calculator displayed in the first post of the thread, you can find it here.

Did you try using it with a camera of matching format? You should at least compare the results out of interest.

Actually due to focus breathing you are unlikely to get a completely accurate result whatever calculator you use.....

[Stagecoach]

The accuracy of Magnification calculators has been discussed many times along with exactly what figures/values you should enter in.

To check any calculator for accuracy and usefulness simply compare to some real world tests.

As an example,



Note : the 2:1 stated in the pic is not accurate. Then we have the different sizes stated for sensors on the same camera, the tolerance of the lens manufactures markings, what is actually achieved by the lens and finally our inaccuracy at determining the measurement of the above result.

For info, the sensor size of the D300 is 23.6 x 15.8mm

Grahame

[george013]

The accuracy of Magnification calculators has been discussed many times along with exactly what figures/values you should enter in.

To check any calculator for accuracy and usefulness simply compare to some real world tests.

As an example,



Note : the 2:1 stated in the pic is not accurate. Then we have the different sizes stated for sensors on the same camera, the tolerance of the lens manufactures markings, what is actually achieved by the lens and finally our inaccuracy at determining the measurement of the above result.

For info, the sensor size of the D300 is 23.6 x 15.8mm

Grahame

Sensor size is not relevant.

George

[Stagecoach]

Sensor size is not relevant.

George

It is relevant to many George when you are interested in 'real world' results of what your camera is going to produce in frame.

[george013]

Graham,
Concerning the subject magnification the sensor size is not relevant. A M of 1 means 1mm object size is 1mm on the sensor. Nothing more and nothing less.

George

[Stagecoach]

Graham,
Concerning the subject magnification the sensor size is not relevant. A M of 1 means 1mm object size is 1mm on the sensor. Nothing more and nothing less.

George

George,

It appears that you want to decide what is relevant to a thread.

My post is not contradicting anything said so far or inaccurate in any way, can you please accept that others have input looking at things in different ways and not everything revolves around your perceptions.

Edit:

To assist you in clearly understanding the post it is showing the commonly used real world practical method of determining 'magnification' of a lens/lens+tube rig. The reference within the post to 'sensor size' is clearly specific to the content of that post and it is absolutely relevant in determining the magnification from the 'result' achieved.

There is no statement or suggestion within that post that is saying magnification is a product of the sensor size.

[pnodrog]

It is and it isn't.... Nearly as bad as quantum mechanics....

If the definition of macro is that the magnification is about 1:1 or greater then sensor size is irrelevant.

However a proposed newer and I think more logical definition (due to changes in technology) of macro is that it starts when a 24mm high subject fills the height of the frame in which case sensor size is relevant.

[Shadowman]

Here is another curveball for the discussion. My 40mm lens I use is specified as having a 1:1 magnification ratio. When I use the method described by Thom Hogan of using the closest focus distance measureable of a mm ruler the magnification ratio is 1:1.45. I was able to autofocus and measure 35mm/24 for a DX camera. Closest focusing distance for my lens is 6inches.

Now if I use the calculator from Mike's link and input 12mm extension tube my calculated magnification ratio is 0.99:1.

http://bythom.com/qadmacro.htm

[DanK]

Graham,
Concerning the subject magnification the sensor size is not relevant. A M of 1 means 1mm object size is 1mm on the sensor. Nothing more and nothing less.

George

Yes, technically, magnification is typically defined as the ratio of the size of the projected image to the size of the subject, so it is independent of sensor size. In practice, however, sensor size and pixel density are relevant to decisions about using tubes. As Graham pointed out, sensor size is relevant if you are determining how large the projected image is relative to the frame. Given equivalent pixel densities, this wouldn't matter, as one could crop the large-sensor image to the size of a smaller sensor and have an identical image. However, in practice, smaller-sensor cameras often have higher pixel density, and that makes sensor size relevant. For example, given the same lens and tube, a given subject at MWD will project the identical image on the sensors of my 7D and 5DIII. However, I always use the 7D when I hunt bugs. The reason is pixel density. Something that fills the frame on the 7D will cover more pixels than the identical image on my 5DIII.

This is exactly the same principle as the greater "reach" of a given lens on a small-sensor camera. If pixel densities were equal, one could crop the large-sensor image and get the same image as with a smaller sensor. In practice, because small-sensor cameras have higher pixel density, one does get more reach with them.

[Mike Buckley]

Yes, technically, magnification is typically defined as the ratio of the size of the projected image to the size of the subject

I've just gotta mention a detail about that because the background is that I saw so often on the Internet that the ratio was defined relative to the size of the sensor, not the size of the projected image. Indeed, I'm grateful that it was you and others who got me straightened out about that inaccuracy. So, now I'm going to take it one step farther and remind everyone that the size of the subject has nothing to do with it; instead, it's the size of the scene being captured. That's because the subject, depending on the photo, could take up 10% or 95% of the scene.

[george013]

Here is another curveball for the discussion. My 40mm lens I use is specified as having a 1:1 magnification ratio. When I use the method described by Thom Hogan of using the closest focus distance measureable of a mm ruler the magnification ratio is 1:1.45. I was able to autofocus and measure 35mm/24 for a DX camera. Closest focusing distance for my lens is 6inches.

Now if I use the calculator from Mike's link and input 12mm extension tube my calculated magnification ratio is 0.99:1.

http://bythom.com/qadmacro.htm

I don't know what you try to tell. As you tell now it's: I did something and the results are different so his story is wrong. First of all: don't introduce another element in your test, the autofocus. Put your lens in the closest distance focusing. And focus by moving the camera. And use liveview. You didn't mention the lens you used, yes 40mm but which one.

That article of Thom Hogan is an excellent article. It's says exactly the same as I try to tell here.

George

[george013]

George,

It appears that you want to decide what is relevant to a thread.

My post is not contradicting anything said so far or inaccurate in any way, can you please accept that others have input looking at things in different ways and not everything revolves around your perceptions.

Edit:

To assist you in clearly understanding the post it is showing the commonly used real world practical method of determining 'magnification' of a lens/lens+tube rig. The reference within the post to 'sensor size' is clearly specific to the content of that post and it is absolutely relevant in determining the magnification from the 'result' achieved.

There is no statement or suggestion within that post that is saying magnification is a product of the sensor size.

With your statements you're introducing a lot of noise in this discussion on magnification. It's independent of framing/sensor size. You've a D800, a FF camera. Take a macro picture with a M=1 and take a second shot with the same distance in DX mode. The picture will be different, M doesn't change.

You didn't mention to what post you're referring, I think it was Dan's post. The formula lens/lens+tube is wrong.. And how it's written in that post lens+tube/lens is also wrong.
What's probably is meant is the internal extension of that lens and to that you add the size of the extension tube. There's a difference between the focal length and the image distance as you must know. I explained that in post 6.

In a macro calculator always the M factor of the lens is asked. With that the calculator calculates the max image distance that lens can physical archive.

I just noticed that the link to "question for the technical gurus" is not a link to this thread but another one. I can't open it. It hangs.


George

[Stagecoach]

With your statements you're introducing a lot of noise in this discussion on magnification. It's independent of framing/sensor size. You've a D800, a FF camera. Take a macro picture with a M=1 and take a second shot with the same distance in DX mode. The picture will be different, M doesn't change.

I repeat once again for you there is nothing in my post No 24 that makes the slightest suggestion that magnification is dependent upon sensor size.

I have cameras with different sensor sizes, am an experienced macro shooter and am very well aware of the the results on different sensors.

Why do you continue to try and read something into a post that is clearly not there and also have the audacity to say that someone is introducing something which is a lot of noise in your opinion. This is a forum where members can partake in discussions and it is not for you to decide what is or is not relevant.

You didn't mention to what post you're referring, I think it was Dan's post. The formula lens/lens+tube is wrong.. And how it's written in that post lens+tube/lens is also wrong.
What's probably is meant is the internal extension of that lens and to that you add the size of the extension tube. There's a difference between the focal length and the image distance as you must know. I explained that in post 6.

Well you thought wrong, and if you had taken the time to read the content, especially the first two paragraphs, rather than looking for the slightest opportunity based on imaginary content to attempt to correct someone and throw in a formulae there would be no need for this.

In a macro calculator always the M factor of the lens is asked. With that the calculator calculates the max image distance that lens can physical archive.

Here you go again, totally off track from anything contained in my post 24 or others by me and trying to lecture me about something so basic, why?

If you wish to point out that something I have stated within a post is inaccurate by all means bring this to the attention of all, this is a learning forum, but please first at least read the post and comment/correct on actual substance and facts contained within it, not what you think I should be saying.

[Shadowman]

I don't know what you try to tell. As you tell now it's: I did something and the results are different so his story is wrong. First of all: don't introduce another element in your test, the autofocus. Put your lens in the closest distance focusing. And focus by moving the camera. And use liveview. You didn't mention the lens you used, yes 40mm but which one.

That article of Thom Hogan is an excellent article. It's says exactly the same as I try to tell here.

George

Who's story is wrong was never mentioned by me, my point of adding the example is that it differed from what the manufacturer (Nikon) stated as the lens magnification factor.

[tao2]

Having read and then reread every post, Ah can see nothing but consistency with all of George's posts, unlike other contributions. With the exception of Pnodrog, there has been a lot of "noise" introduced - but let me be more accurate here...both Dan and Grahame have introduce strawman arguments and hasty generalisations do not resolve arguments...ever...

[Stagecoach]

Having read and then reread every post, Ah can see nothing but consistency with all of George's posts, unlike other contributions. With the exception of Pnodrog, there has been a lot of "noise" introduced - but let me be more accurate here...both Dan and Grahame have introduce strawman arguments and hasty generalisations do not resolve arguments...ever...

It would be interesting to hear what 'argument' or 'generalisations' you consider is contained within my post?

[george013]

I repeat once again for you [B][U]there is nothing in my post No 24 that makes the slightest suggestion that magnification is dependent upon sensor size

Well, then we agree with that.

Well you thought wrong, and if you had taken the time to read the content, especially the first two paragraphs, rather than looking for the slightest opportunity based on imaginary content to attempt to correct someone and throw in a formulae there would be no need for this.

Try to be more specific. Are we talking about the link Dan gave? I think we're. What does the first two paragraphs say?

Just some comments on my understanding of the magnification achieved when using extension rings on macro and non- macro lenses.
With normal non- macro lenses, magnification seems straight forward. You can use the formula tube length (mm)/ lens focal length mm and get an answer that seems to work.

And do you think this formula is correct???? Reading it over he's not sure himself. But he think he can work with it. And further in that article he writes the results are not always good. But he's looking for the wrong reasons.



It's a post from 2005. When he reads that back he might be shamed. But I don't blame him but the people that defend or using his "theory". As I said before, when it's repeated long enough it becomes true.


To give you the formula as it should be as I think (image distance-focal length)/focal length.
It's about the space between lens and sensor, the image distance. And within that the ratio lens-focal point and focal point-sensor.
Exactly as how the calculators work.

George

George

[Stagecoach]

Well, then we agree with that.






Try to be more specific. Are we talking about the link Dan gave? I think we're. What does the first two paragraphs say?

And do you think this formula is correct???? Reading it over he's not sure himself. But he think he can work with it. And further in that article he writes the results are not always good. But he's looking for the wrong reasons.



It's a post from 2005. When he reads that back he might be shamed. But I don't blame him but the people that defend or using his "theory". As I said before, when it's repeated long enough it becomes true.


To give you the formula as it should be as I think (image distance-focal length)/focal length.
It's about the space between lens and sensor, the image distance. And within that the ratio lens-focal point and focal point-sensor.
Exactly as how the calculators work.

George

George

George,

Out of respect for this forum and Mikes thread I will not spend any more of my time correcting you other than this;

There are no references implied in my post 24, to either other posts OR links, it is a basic practical method of determining magnification and can also be used for verifying a 'calculators' results (within the realms of tolerance).

Take time to read posts, if unclear ask questions not start making rash assumptions and trying to tell someone they are wrong or do not know what they are talking about.