How to deal with the central bright spot

Teamspeed:
I repeat, whatever you may infer from the article, there is no use or understanding of the word "math" in English English. The last line of the article is not referring to English English, or is incorrect.

I initially wrote that the term "Macro lens" has no bearing on this discussion, which it hasn't. It's pretty meaningless. People think "Macro lenses" are special - they are not, for this discussion. Their construction doesn't alter the maths. That WAS part of what you may have replied to.
I thought I removed it before there were any replies - it was gone within minutes, because I thought someone would misunderstand.

You have misinterpreted the thread, and the quote, and brought irrelevant matters into the post so you could pick a fight - including semantics.

You asked

So I gave you a reference which adequately explains. You still wanted to argue.

You also said

. Clearly. So you go off in different directions? If you'd asked, I would have explained again.

You went on about lenses being close or not to the sensor - irrelevant AND nonsense.

"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," All The underlined part doesn't make much sense in any language; we aren't discussing light and shutter speeds - or any need "to learn" bracketing. (How arrogant!)
If you think there's no need for large aperture lenses in macro, you're badly mistaken, as explained - part of the "not following", I imagine. Try reading again.

.


Dog give us strength.

-----

I see you have posted some pictures.
As anyone would have predicted, they don't show the OP's problem, which was caused by the reason I gave in my first post in the thread. It's very well understood and controlled by experienced macro shooters.

Interesting stuff and nice macros. I am going on a trip and intend to put the old 18-55 kit on my tubes, see if I run into spot troubles still. The tubes are fotodiox, I assure you I paid under $15 for the set. Inside is also black anodized aluminum with threading on the interior.

Those are shiny tubes, the more you use the worse the problemis likely to be.
As above, you need to look at the adapters too.

Cheap black paper in a tube/cone, or a disc with a hole in it, can be all it takes to stop it.
Disc - you may have noticed the more effective rectangular hole which is put in some tubes and lenses?

Here's a round one:
https://www.flickr.com​/photos/steve_snaps/38​35640272

Rectangular:
http://www.photomacrog​raphy.net …topic.php?p=120​345#120345

If you reverse any lens, you're more likely to need a lens hood, for the exposed rear end, too.

Thanks, I'll have to look into the baffling. I assume a rectangular baffle opening would need to stay aligned to the sensor position, whereas the circular baffle wouldn't matter?

Chris.R wrote in post #18236225
Those are shiny tubes, the more you use the worse the problemis likely to be.
As above, you need to look at the adapters too.

Cheap black paper in a tube/cone, or a disc with a hole in it, can be all it takes to stop it.
Disc - you may have noticed the more effective rectangular hole which is put in some tubes and lenses?

Here's a round one:
https://www.flickr.com​/photos/steve_snaps/38​35640272

Rectangular:
http://www.photomacrog​raphy.net …topic.php?p=120​345#120345

If you reverse any lens, you're more likely to need a lens hood, for the exposed rear end, too.

Benitoite wrote in post #18236231
Thanks, I'll have to look into the baffling. I assume a rectangular baffle opening would need to stay aligned to the sensor position, whereas the circular baffle wouldn't matter?

Exactly so.

If the tubes are any length, just eyeball into the back of them and tip the lens towards light. You often see reflections off things.
The sensor itself is reflective though so when the assembly is on the camera, something like a small shiny flat part on an adapter can cause a problem you wouldn't guess.
As an example, if you reverse a lens and leave a filter on the reversed end, you can get a dramatic demonstration with some setups, nothing with others.

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.

I think in the digital age the distinction between lens normality and super-macro is right at the 1:1 spot. Sure you can go across the break continuously, but in practice we tend to have more individual lens speciality. I believe some would say the distinction is even more to do with the minimum working distance. Others might argue it's how they compare optically with the eye.

Chris.R wrote in post #18236225
...
If you reverse any lens, you're more likely to need a lens hood, for the exposed rear end, too.

Is that due to illumination issues, or just protecting the surface of the lens there?

TeamSpeed wrote in post #18235786
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.

Hosted photo: posted by TeamSpeed in
./showthread.php?p=182​35786&i=i151616147
forum: Macro

Hosted photo: posted by TeamSpeed in
./showthread.php?p=182​35786&i=i73764142
forum: Macro

Yes this is what I get with all three macro lenses I use.

I used to do this regularly for dust spot detection/ sensor cleaning before Canon introduced self cleaning sensors.

Chris R and Teamspeed, stop arguing in the OP's thread, it is disruptive, take your argument to PMs if you must.

Benitoite wrote in post #18236248
I think in the digital age the distinction between lens normality and super-macro is right at the 1:1 spot. Sure you can go across the break continuously, but in practice we tend to have more individual lens speciality. I believe some would say the distinction is even more to do with the minimum working distance. Others might argue it's how they compare optically with the eye.

Formally macro photography is in the range 1X to 10X, above 10X is microphotography.

Macro lenses are characterised by being optimised for performance and aberrations at the closeup (<1X) range to low macro range. They normally manage at least 1X unaided with the odd exception.

The term Macrophoto lens is normally applied to lenses for >1X use, notably the MP-E 65mm 1X-5X and of course the screw mount lenses for bellows systems.

Hope that helps.

Benitoite wrote in post #18236250
Is that due to illumination issues, or just protecting the surface of the lens there?

"It's assumed" that the rear end of the lens isn't designed to have light coming from all directions.
Anyway, it's a common finding that they need some protection. A tube of black paper, or a short expension tube, will serve.

Lester Wareham wrote in post #18236263
Formally macro photography is in the range 1X to 10X, above 10X is microphotography.

Or "photomicrography".

Lester Wareham wrote in post #18236263
Formally macro photography is in the range 1X to 10X, above 10X is microphotography.

Macro lenses are characterised by being optimised for performance and aberrations at the closeup (<1X) range to low macro range. They normally manage at least 1X unaided with the odd exception.

The term Macrophoto lens is normally applied to lenses for >1X use, notably the MP-E 65mm 1X-5X and of course the screw mount lenses for bellows systems.

Hope that helps.

I don't think it does help, except to list the popular, rather unreliable views.
What does 1x mean?
Life size where?
On the sensor?
On the computer screen?
On some other size print?

Suppose I photograph an 18mm fingernail :
If I use a 24 x 36 sensor, it's 2x
If I use a 6 x 4mm sensor, it's 0.3x.
Which is "macro"?

"optimised for performance and aberrations at the closeup (<1X) range to low macro range" Not in my experience. If you want to go closer than 1:1, you'd better reverse them.
A few go both sides, but of the number of what would be called Macro lenses I have which do that, ONLY the ones which are sold as "1:1" lenses are designed not to need reversing.
On the other hand, MANY very good "macro lenses" only go to 0.5x (Half life size) That includes models from Leica, Nikon, and Sigma at least.
They call them Macro Elmarit, etc? Are they wrong? I'd say not.
Perhaps you meant that 0.1x to 1:1 is "Low macro" - I don't know. ?

"above 10X is microphotography." No. I thnk the accepted term is photmicrography.
Microphotography being the production of very small photographs.


I tried to make the case above that it doesn't matter a jot what the maufacturer calls the lens, only what the maths, mathematics, math or whatever anyone wants to call it, predicts.

We can say that "consumer" "Macro lenses" from the main manufacturers are designed to focus closer than their others, but that's about all that's safe, as far as I'm aware. To be honest, that'll DO, won't it??
Generally macro lenses are designed to focus much closer than infinity. Some (most modern ones) are better corrected to do it, some aren't. Some have mechanical arrangements to help, some do not. Some very good lenses for 1:1 and beyond, don't bear the word "Macro" .

I'm quite happy to call a picture of my palm, or thumb, a macro photo or not a macro photo.
If I used my old 10x8" for a portrait of a child at 1:1, is that Macro? Frankly I don't care.

I do care when apparently authoritative assertions have the potential to mislead.

Chris.R wrote in post #18237779
I don't think it does help, except to list the popular, rather unreliable views.
What does 1x mean?
Life size where?
On the sensor?
On the computer screen?
On some other size print?

Suppose I photograph an 18mm fingernail :
If I use a 24 x 36 sensor, it's 2x
If I use a 6 x 4mm sensor, it's 0.3x.
Which is "macro"?

"optimised for performance and aberrations at the closeup (<1X) range to low macro range" Not in my experience. If you want to go closer than 1:1, you'd better reverse them.
A few go both sides, but of the number of what would be called Macro lenses I have which do that, ONLY the ones which are sold as "1:1" lenses are designed not to need reversing.
On the other hand, MANY very good "macro lenses" only go to 0.5x (Half life size) That includes models from Leica, Nikon, and Sigma at least.
They call them Macro Elmarit, etc? Are they wrong? I'd say not.
Perhaps you meant that 0.1x to 1:1 is "Low macro" - I don't know. ?

"above 10X is microphotography." No. I thnk the accepted term is photmicrography.
Microphotography being the production of very small photographs.

I tried to make the case above that it doesn't matter a jot what the maufacturer calls the lens, only what the maths, mathematics, math or whatever anyone wants to call it, predicts.

We can say that "consumer" "Macro lenses" from the main manufacturers are designed to focus closer than their others, but that's about all that's safe, as far as I'm aware. To be honest, that'll DO, won't it??
Generally macro lenses are designed to focus much closer than infinity. Some (most modern ones) are better corrected to do it, some aren't. Some have mechanical arrangements to help, some do not. Some very good lenses for 1:1 and beyond, don't bear the word "Macro" .

I'm quite happy to call a picture of my palm, or thumb, a macro photo or not a macro photo.
If I used my old 10x8" for a portrait of a child at 1:1, is that Macro? Frankly I don't care.

I do care when apparently authoritative assertions have the potential to mislead.

Linear magnification is always defined as image on sensor to object size ratio.

TBH I have a relaxed attitude about these conventional ranges, but they have been around a very long time, so it makes sense to use them to avoid all the cercumlocations.

Even today they relate well to the equipment mostly used for them.

Lester Wareham wrote in post #18238501
Linear magnification is always defined as image on sensor to object size ratio.

If you read widely, you'll find it definitely is not "always", and for varying very good reasons. The reasons depending on the context.

You haven't commented on the inconsistencies I pointed to in your previous answer, we so we don't know whether you mean, eg 1:2.5, = 0.4x, = "40% of life size" to be what you declared as "macro" or not.
I think you meant that it would not be, since you defined 1x (=1:1) to 1:10 (=10x) as macro.
Therefore several excellent "Macro Lenses"(as listed) by your definition are not capable of macro photography, so presumably aren't macro lenses at all.

(I see the invention of a new term "macrophoto lens" - nobody uses that to my knowledge. Canon use Macro Photo (note , as two words not one) for one of their current lenses. It makes no sense to corrupt one manufacturer's Trade Name for one of their lenses and apply it as a generality.)


I could fill the screen with a picture of the blunt end of a pencil, but you could't tell me whether it were a "macro" photograph taken with a "macro lens" or not. Even if you did have the definitions straight!

It's well within the range of a modern very ordinary camera (without cropping) or very ordinary microscope.
I'd be quite happy to call it a macro photograph - it's a photograph of a small thing.


This leads me to urge anyone to stop making authoritative-sounding assertions, expecially when they contain glaring inconsistencies which remain uncorrected.


Some conventions which applied in 35mm days don't apply any more, and are grossly misleading. Sites like this one have a responsibility to deepen understanding, and NOT support dogged adherence to accustomed misconceptions using in some cases, specious arguments and feeble distraction.