How to deal with the central bright spot

There are no such discrete entities as normal and macro. There's s no "break down". Most of the same maths can be used throughout, it's a continuous range.
The results of the maths can become unfamiliar (eg angle of view, how much light gets through the lens, rules about vibration etc) such that comfortable rules of thumb are no longer useful.
The curve in the nice linear relationships becomes quite pronounced as you work towards and around 1:1, because the lens is so far extended from the sensor.

When you go closer than 1:1, you start to need a some extra maths because light's a wave, and diffraction will blur what you thought would be in focus. It was always there at longer distances, but the effect wasn't normally significant. At around perhaps 3x, its getting to be quite a problem.

When you go really close - micro really, at beyond say 10x, the same maths will tell you that it's only the aperture and nothing else, that controls DOF. The physics means you can't have lenses with large enough apertures to do what you really would like.

^ What the heck is "the maths", and there are 1:1 macro lenses that are not very far from the sensor like the 50mm macro vs something like a 180mm macro. Also if you want to shut down your aperture for larger DOF, then it isn't really a lens issue allowing for large apertures, but rather a light/exposure/ISO issue vs fast enough shutter speed at that point. This is why you really need to learn to focus bracket your results, instead of using aperture on a single exposure to control the final DOF. I really don't follow anything that was said above, I apologize.

A macro lens is different than other lenses because they provide enough "minimum focusing distance" to allow your subject material be projected at a 1:1 representation onto the sensor, a distinction non-macro lens cannot claim, so a true 1:1 or larger magnification macro lens definitely offers something different than a "normal" (ie. non-macro) lens.

Chris.R wrote in post #18232650
There are no such discrete entities as normal and macro. There's s no "break down". Most of the same maths can be used throughout, it's a continuous range.
The results of the maths can become unfamiliar (eg angle of view, how much light gets through the lens, rules about vibration etc) such that comfortable rules of thumb are no longer useful.
The curve in the nice linear relationships becomes quite pronounced as you work towards and around 1:1, because the lens is so far extended from the sensor.

When you go closer than 1:1, you start to need a some extra maths because light's a wave, and diffraction will blur what you thought would be in focus. It was always there at longer distances, but the effect wasn't normally significant. At around perhaps 3x, its getting to be quite a problem.

When you go really close - micro really, at beyond say 10x, the same maths will tell you that it's only the aperture and nothing else, that controls DOF. The physics means you can't have lenses with large enough apertures to do what you really would like.

Yes, sorry. Bad choice of words. I was trying to keep the response simple without getting into dominant factors or attractors. I understand that the math doesn't fail or break down. Just that at some point, certain terms become more or less significant. My purpose was to offer thanks.

It's what tells you your depth of field, and everything else. We're talking about lens optical behaviour here, so shutter speeds and light levels and mechanical construction around the glass, are irrelevant.
Whether or not a lens says "macro" on it, or however close the mechanics let it focus, also make zero difference to DOF (etc) at the same magnification and aperture.
The implication in the previous post(s) was that there is a macro and a "normal" set of rules. There isn't. Same mathematics, different numbers. But, towards or away from extremes, it works out that simpler formulae become less or more useful.

"Macro" is one of those terms that's fairly useful but you can't really rely on for much, without adding a lot more words.
Of my best two macro-use lenses, one doesn't say macro on it, and neither will focus at all without a bellows or similar.

That http://www.zyoptics.ne​t ...f2-4-5x-super-macro-lens/ certainly doesn't get used "close to the sensor"!
(By the way it's apparently a Chinese copy of the Olympus 20mm f/2, and not particularly good, though not bad value for some.)

So the mathematics, or math, or physics, not maths.... got it. Your terminology is very confusing. Also, macro lenses are different functionally than the rest of the lens lineup, so it is misleading to say there is no difference between them.

However yes, the same factors in capturing an image are no different with these different sets of lenses. Physics is physics.

"Maths" is the shortened form of the word "Mathematics" in English.
"Not maths" is wrong!
As Here
"Math" is never used in the UK.

No, we are discussing the meaning of the word, not a meaningless classification of hardware. We are discussing what happens when you focus close - however you choose to do it, doesn't matter a jot. The maths is the same.

I think you must have misread or misunderstood the previous posts.
Start with the OP in post #1, he's not using a "Macro" lens. He's using the most ordinary of lenses.
It's important to separate the manufacturers' assignations from what's really going on.

1. If you read the link you provide, you don't use maths, you use mathematics. Maths is used if you are talking about studying mathematics in school but not when you are talking about the science itself.

2. I am addressing just your reply that there isn't a difference between a macro lens and other lenses, not the previous posts.

3. I already agreed that physics are the same for either type of lens, or type of situation being shot.

4. In any case, none of this deals with the original post, the situation here is that the lens or tubes are causing the issue, and isn't a symptom of shooting macros.

Chris.R wrote in post #18235130
"Maths" is the shortened form of the word "Mathematics" in English.
"Not maths" is wrong!
As Here
"Math" is never used in the UK.

The above link says

"Mathematics is the study of numbers, quantities, and shapes. When mathematics is taught as a subject at school, it is usually called maths in British English, and math in American English.
Maths is my best subject at school.
Julio teaches math at a middle school.
Be Careful!
Mathematics, maths, and math are uncountable nouns and are used with a singular verb. Don't say, for example, 'Maths are my best subject'."

Is Chris.R British or American?

"the maths"

This word can get you looked at sideways in California.

I can't say I have noticed this with modern macro lenses although all lenses with have some vignetting it should not be anything like this.

I have that FD lens (still have somewhere) and used to use it on tubes for macro in film days, to be honest it was not great, I don't remember this issue however.

I would recommend investing in a modern macro lens of about 100mm length, you will get great results very easily.

And you left off the very next sentence from that link, which was what I was referring to.

But you'd still be wrong .

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I use English, you use a distorted form of it. You may not tell me what words to use, so there
The way I used them, was perfection exemplified!

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No, you aren't. You invented that I had said something about macro lenses, presumably so you could argue against it.
In both languages, I believe, that's called trolling?

Chris.R wrote in post #18235728
But you'd still be wrong .

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I use English, you use a distorted form of it. You may not tell me what words to use, so there
The way I used them, was perfection exemplified!

---

No, you aren't. You invented that I had said something about macro lenses, presumably so you could argue against it.
In both languages, I believe, that's called trolling?

1) You provided the link, and I am just pointing that the material you use to correct me clearly states to not use maths when you are talking about the science.

2) I cannot point out what I was clarifying on your post, because you have since edited it and removed the comment upon which I replied. It doesn't really matter at this point anyways. A macro lens that is marketed as such is different than a normal everyday lens because it is designed to do something that the other lens cannot. However, it seems you weren't commenting on that, even though the original content, pre-edit, sounded like that.

I am not trolling, and never have in the 12 years of being on this board. If you are communicating in a way that others aren't understanding, but you insult them about their use of language, etc, when they try to get clarification, who really is trolling? I could care less about what version of English you are using, because it doesn't make you better, or more right, it is just one of a thousand languages, and I found your terms confusing, that is all.

In any case, you have had your say, let's get back to the subject of this thread. I am curious whether the situation has been remedied by using different tubes or reducing the reflections inside the tubes/lens.

Benitoite, here is what I get with my Canon 100L Macro lens. I tried an f22 shot on a wall (looks like I need to clean my sensor), then took this salt picture. I have shot with 4 other 1:1 macro lenses and also have not seen this behavior with them. What kind of tubes are you using? (brand, etc)

The least expensive 1:1 Canon AF-enabled macro lens that I am aware of is the Sigma 50mm f2.8 macro, at just over $200. I know you are trying to do this kind of photography with a very low investment, so I doubt this is something you might consider, but I thought I would offer that info up.

This is with one of my 3 tubes on the 100L, using my Wiha smallest torque bit (as I undertake a project). I have no idea what magnification this is, but again, I don't see discoloration in this.