'MACRO' pound coins [Archive]

cowasaki

30-12-2007, 18:40

Great that you have got them working well. What make are they? Do they transfer focus info etc from the lens or do they make it all manual (like mine do). My macro tubes cost £26 for TWO sets inc delivery!!

After your first post I got my macro tubes out having bought them when I bought all my kit a few months ago and not yet used them. They didn't come with instructions and I haven't seen any instructions for their use so I didn't realise just how much light you loose! When I tried to use them at first I didn't get anything but when I switched to manual I have actually got some shots. Nothing worth sending in yet as I have blown both the bulbs in my spots so had to guess the focus and shoot off my flash five times during the exposure! I will submit some when I get some new bulbs!

Oh if anyone wants the address for a UK supplier who sells macro tubes at about £15 per set inc postage let me know and i'll try and dig it back out. They are not brilliant quality as you can imagine but as there is no glass in a macro tube they do the job and its not a lot to pay for something to have a play with!

michaelho

30-12-2007, 19:59

Thanks for all your comments. Yes that is a two 'pound coin' added in there as I needed the 'R' to spell out 'MACRO' :p Also added little borders on the top and bottom with pound coins that have a pattern around the edge haha.

I am using the Jessop branded extension tube kit (13, 21 and 31mm) which can be had for a bargain price of £22.49!

For this shot I used my Tokina 100mm f2.8 Macro lens with either the 21mm or the 31mm tube attached. Also used a tripod, remote release and 580Ex flash with lightsphere diffuser attached to it.

cowasaki: there's not much else involved in using extension tubes, I have found that I first start off with just the macro lens attached to the camera to see how close it gets on it's own, then I add on the extension tube depending on how much closer I want to get. Position the camera in the right position and focus the subject. These tubes work with Canon's AF system but I tend to use manual for my macro shots anyway so I get exactly what I want in focus.

Alex S

30-12-2007, 20:01

A clever shot, very well executed :thumbs:

michaelho

30-12-2007, 20:03

I'm assuming its a crop

I have only cropped a little bit from the top and a little bit from the bottom, that's it. The extension tubes on a macro lens can really get you in close.

AWP: I usually save my jpegs with max. quality setting, would middle quality setting be sufficient?

Ally

30-12-2007, 20:39

Nice shot, I would possibly have gone for a bit softer lighting as the harshness of the highlight is a bit distracting imo. Great thought with the word :thumbs:

michaelho

30-12-2007, 20:52

yeah I agree Ally. This shot would have definitely benefited from off camera lighting, but I don't have a wireless transmitter or a hot shoe cord. With the extension tube attached the camera was very close to the stack of coins therefore the mounted flash provided light from an acute angle very close to the coins. If I could I would have moved the light more central and further away from the coins to give a more even lighting.

spencer

30-12-2007, 21:12

Great shot, very clear!

Like the "MACRO: wording as well!

Spence

whiteflyer

30-12-2007, 21:53

That is too clever by half :lol:

Ugs

30-12-2007, 22:04

Great shot, very clear!

Like the "MACRO: wording as well!

Spence

Oh! - I thought he meant the "ate em"

:)

DaveHope

30-12-2007, 22:07

Great shot! - Might have a go at reproducing it. What sort of lighting setup did you have for the shot? - I know you said you had a difuser, but did you have it in a light box or anything like that?

Blue Moon 7

30-12-2007, 22:08

Excellent stuff. Clever as well.

Chris

michaelho

30-12-2007, 22:29

lol 'ate em', is 'MACRO' not very obvious? I tried to hint by highlighting 'MACRO' in the topic title :p

Thanks again for your comments.

DaveHope: No lightbox involved, stacked the coins on a piece of A4 paper, set up the camera on a tripod, mounted my flash on the camera and put a lightsphere diffuser on the flash then just shot away using remote shutter.

EdinburghGary

31-12-2007, 04:06

Cooooooooool photo. How do extension tubes work?

KenCo

31-12-2007, 10:57

Good shot and well thought out!

cowasaki

31-12-2007, 11:06

Cooooooooool photo. How do extension tubes work?

They are a collection of empty tubes which move the lens further away from the sensor so that only part of the light hits it. Each tube is a different length allowing lots of different magnifications. At its maximum magnification maybe only the central 10% of light that hits the lens gets the the sensor so this is spread out over the same area and is effectively magnified optically which is much better than say cropping out the central 10% of your picture and then resizing it. Because they are just basically empty tubes with a mount at each end they are quite cheap. Some pass the electronics between lens and camera and are more expensive some do not and can be as cheap as £10-15.

Because they spread this light out over a wider area tubes are much darker than a proper macro lens and as such it is like stopping down a long way. My bulbs all blew on my macro lamps so to get a picture with all the tubes attached I needed a 30 second exposure with 5 flash gun flashes during it! I am looking forward to messing with them when I get some more bulbs!

pxl8

31-12-2007, 11:22

The light loss has nothing to do with the magnification letting less light in, it's because the light has to travel further and the inverse square rule starts to have an effect.

cowasaki

31-12-2007, 11:40

The light loss has nothing to do with the magnification letting less light in, it's because the light has to travel further and the inverse square rule starts to have an effect.

If you let x amount of light through the end of a tube then the length of the tube dictates how much light comes out of the other end (unless it is a beam) as you say but this is because only a small amount of the light that enters hits the object, which is what I was saying. Ie if the picture is 10% of the size then the light hits that hits the sensor will be (.1x.1 = .01th) as much or 1% as bright. It has nothing to do with just how far the light travels. Its the same principle as looking at a star hundreds of light years away. It looks dim because effectively you are only looking at a minute percentage of the light in much the same way as a macro tube. Light does not just dim over a distance* or your 500mm 40cm long lenses would be rubbish. They have a bigger front glass to let more light it so allowing a bigger percentage of that light to hit the sensor.

I might not know much about photography but I know about Physics! :-)

* this is the conservation of energy principle. Light may dim by a tiny amount as it hits dust etc but over 8cm there would be no measurable loss.

pxl8

31-12-2007, 11:47

I might not know much about photography but I know about Physics! :-)

http://en.wikipedia.org/wiki/Inverse_square_law

The same law is used to calculate exposure for all type of lighting and also to calculate the exposure correction when using tubes or a bellows set.

Sorry but you're just plain wrong.:shrug:

pxl8

31-12-2007, 11:50

I'll add, as it might help, that it's important to remember that a camera records the amount of light arriving at the sensor/film plane and not how much light is at the point in space it is pointing at.

cowasaki

31-12-2007, 12:11

If you look at your link to wikipedia it nicely explains exactly what I am saying!!

I am just going back to simple principals the amount of light that hits the sensor is less because only a small percentage of the light entering it gets to the sensor like I explained. If you think about it we are saying the same thing. I was just explaining why. Saying that it is because of the distance is simplifying it too much. The light itself does not dim over distance it is spread out so less is hitting just like your diagram explains. If you still don't get it I will do another diagram showing a camera lens with and without the tubes

cowasaki

31-12-2007, 12:32

Pixl8, we really are saying the same thing! Here, I have done a diagram with photoshop (yes I know its a bit rubbish but it does explain how a macro tube works and the loss of light!)

http://www.talkphotography.co.uk/gallery/data/500/macro-tube.jpg

Basically with the lens fitted normally the sensor would be at pos A.

With a small tube the sensor is effectively at pos B. Just like you said the inverse-square law applies BUT all that is saying is what I was saying it was just that I was explaining it in laymans terms. Less of the light coming from the lens hits the sensor making the picture darker. (and this percentage is related to the magnification)

With a longer tube the sensor is effectively at pos C again the picture is magnified further but less of the light is hitting the sensor so it is darker still.

Just take a look at the diagram we really are saying the same thing I am just trying to explain it using simple principals :)

pxl8

31-12-2007, 12:52

With a small tube the sensor is effectively at pos B. Just like you said the inverse-square law applies BUT all that is saying is what I was saying it was just that I was explaining it in laymans terms. Less of the light coming from the lens hits the sensor making the picture darker. (and this percentage is related to the magnification)

You're still hung up on the magnification but it's got nothing to do with the reduction of light.

If you put a 25mm tube on a 50mm lens the magnification is greater than putting the tube on a 100mm lens. But the light loss is the same for both. The light loss has NOTHING to do with the magnification only the distance the light travels - the further it travels the more it will spread (and that's got nothing to do with the magnification).

cowasaki

31-12-2007, 12:58

You're still hung up on the magnification but it's got nothing to do with the reduction of light.

If you put a 25mm tube on a 50mm lens the magnification is greater than putting the tube on a 100mm lens. But the light loss is the same for both. The light loss has NOTHING to do with the magnification only the distance the light travels - the further it travels the more it will spread (and that's got nothing to do with the magnification).

The light spreading out is what CAUSES the magnification the reduction in amount of light is caused by this spread (not caused by the distance) but it is completely linked to the amount of magnification. I am not hung up on the magnification that is just how it is, we both clearly understand how it works we are just explaining it from alternative directions! If you look at my diagram and the one you found on wikipedia they really are the same thing!

michaelho

31-12-2007, 13:01

I think you both are talking about the same thing, it's just that cowasaki is refering to magnification regarding the use of one specific lens. E.g. if you use a 31mm tube it's more highly magnified compared to using a 21mm tube with the same lens, and this extra magnification is a confounding factor to the extra distance of the 31mm tube which reduces the light hitting the sensor.
Pxl8 is just saying that magnification is just a confounding factor and actually does not affect the amount of light, it's actually the extra distance the tube moves the lens away from the sensor that is the real determinant of how much light hits the sensor.

Sounds right?

michaelho

31-12-2007, 13:03

nice diagram btw cowasaki :p

cowasaki

31-12-2007, 13:09

nice diagram btw cowasaki :p

Thanks, I think it explains how it works! This kind of arguement happens a lot on forums. Two people basically saying the same thing. Pixl8 obviously understands it just like I do but we have looked at explaining it in a different ways!

michaelho

31-12-2007, 13:13

not just forums, I find myself arguing the same arguments with my girlfriends. She just has to win.....but then again so do I lol.

cowasaki

31-12-2007, 13:15

girlfriends.

There will be even more arguements if they both find out!

pxl8

31-12-2007, 13:20

The light spreading out is what CAUSES the magnification the reduction in amount of light is caused by this spread (not caused by the distance) but it is completely linked to the amount of magnification.

If I understand the above you're saying that because the image being resolved is spread further out (magnified) less light reaches the sensor?

Yes?

cowasaki

31-12-2007, 13:25

If I understand the above you're saying that because the image being resolved is spread further out (magnified) less light reaches the sensor?

Yes?

Yes I am, I was just trying to explain that the greater the magnification the less light. The distance and magnification are inextricably linked so if either increase so does the other (for any given camera/lens). So yes we are completely saying the same thing I was just trying to explain it without getting too scientific! ;)

michaelho

31-12-2007, 13:28

is there a law which links distance and magnification?

cowasaki

31-12-2007, 13:35

is there a law which links distance and magnification?

effectively it is about the inverse-square law! As the distance increases so does the magnification. This will depend on the camera/lens combination but it will always increase. I fancy a set of baffles or a telescopic tube. I might even have a mess and look at making one..... Where is that sticky back plastic, fairy bottle and packing tape?

michaelho

31-12-2007, 13:44

pxl8

31-12-2007, 13:45

If the "spread" were the defining factor then why don't exposure settings change between full frame and crop sensors?

michaelho

31-12-2007, 13:49

cowasaki

31-12-2007, 13:53

The inverse square law only deals with distance i.e. doubling the distance between the light and the subject results in one quarter of the light hitting the subject.

If there was a law to link distance and magnification then magnification would be directly linked to the inverse square law. Otherwise I think magnification is just a confounding factor.

Magnification is directly linked to distance as can be seen from either diagram. Whether it is perceived to be a confounding factor or not does not really matter. The point is that as the magnification is increased the amount of light hitting the sensor decreases which was what I was saying originally due to the reason I originally stated. You can look at it from either way but if you just explain it using distance as the important factor then it has a tendency to look like you are saying that light itself reduces in intensity as it moves through space which it doesn't (it spreads out so you see less). Either way explains the principal and I am sure that anyone reading this thread now understands how/why this happens.

cowasaki

31-12-2007, 13:56

pxl8 gave a really good example: using a 25mm tube on a 50mm lens will give a different magnification than if used on a 100mm lens, however the amount of light loss is the same. Therefore light loss cannot be attributed to magnification, it is just a confounding factor.

If you look at my responses I have said "for the same camera/lens combination" and as magnification increases the amount of light at the other end decreases. If the magnifcation is 8X then then light reduction is 8X8 (8x in each direction) ie one 64th. This does not require anyone to know distance, lens or anything else it is a simple mathematical principal.

cowasaki

31-12-2007, 14:01

If the "spread" were the defining factor then why don't exposure settings change between full frame and crop sensors?

Because the lens is giving the same amount of light across the area. On a smaller sensor you are only looking at a small part of it. The cropped sensor is not magnifying anything it is just a small subset of a full frame sensor in the same position.

michaelho

31-12-2007, 14:05

yep I agree, for the same lens combination that is in fact what happens. As distance increase so does magnification, therefore the further away the tube takes the lens the higher the magnification and also the less amount of light hitting the sensor.

What we are trying to point out is that it is not magnification per se but it's actually the distance which causes the light to be loss due to the spread of flux/energy. This spread of flux is constant with distance that's why the amount of light hitting the sensor at a certain distance from the subject is the same no matter what magnification.

But we are just going round in circles, end of the day the extension tubes takes the lens further away from the sensor, thus giving a larger magnification due to the extra distance which will result in less light hitting the sensor.

cowasaki

31-12-2007, 14:06

This is getting silly, it is like arguing over how far you can throw a round rock made of granite and one person saying it depends on the weight of the rock and another saying it depends on the size. They are effectively arguing the same thing as the size increases so does the weight. In our example as the distance increases so does the magnification. I chose to relate the light loss to magnification on the basis that it is much easier to explain WHY there is a light loss when you explain it this way ie 8x mag produces 64th the amount of light. Yes I agree it is due to distance but distance increases the magnification so as you increase magnification you increase light loss.

:bang::bang::bang::bang::bang::bang:

pxl8

31-12-2007, 14:06

Magnification will affect the amount of light and in the way you described but compensating for that doesn't compensate for the light loss from the addition of the tubes.

If you have a "normal" macro lens and point it at a evenly lit white wall at 1:2 (half life size) and take a reading and then take another reading at 1:1 you'll get a lower reading. This is the effect of magnification because you are looking at a smaller subject area so less light will be reflected into the lens.

It's got nothing to to do with the image circle projected onto the sensor/film plane as that stays the same size, it's just the result of how much light can enter the front of the lens. If you were to have infinite magnification then then amount of light reflected back would be infinitely small.

This doesn't compensate for the addition of tube. The inverse square law deals with the spreading of light (except colminated light from a laser, etc) and that spread happens along the length of the tube - the longer the tube the more the light will spread and the greater the reduction in light hitting the sensor. Don't be fooled into thinking that because the light has been focused it won't spread, that's only true if the light is a parallel beam like a laser.

michaelho

31-12-2007, 14:15

it's an interesting discussion and I for one am glad to have brushed up a little on physics and have learned a bit more of the technical side of photography.

cowasaki

31-12-2007, 14:21

Magnification will affect the amount of light and in the way you described but compensating for that doesn't compensate for the light loss from the addition of the tubes.

Nobody is talking about any form of compensation. If you increase the distance you increase the magnification therefore using the simple example of a macro tube distance and magnifcation are TOTALLY linked and you could talk about either.

If you have a "normal" macro lens and point it at a evenly lit white wall at 1:2 (half life size) and take a reading and then take another reading at 1:1 you'll get a lower reading. This is the effect of magnification because you are looking at a smaller subject area so less light will be reflected into the lens.

It's got nothing to to do with the image circle projected onto the sensor/film plane as that stays the same size, it's just the result of how much light can enter the front of the lens. If you were to have infinite magnification then then amount of light reflected back would be infinitely small.

Yes I understand this but using the lens in this manner is using lenses to focus that light. This changes everything and has nothing to do with the SIMPLE model we were looking at originally ie MACRO TUBES.

This doesn't compensate for the addition of tube. The inverse square law deals with the spreading of light (except colminated light from a laser, etc) and that spread happens along the length of the tube - the longer the tube the more the light will spread and the greater the reduction in light hitting the sensor. Don't be fooled into thinking that because the light has been focused it won't spread, that's only true if the light is a parallel beam like a laser.

I am only talking about magnification due to distance not using lenses. I am STILL agreeing with you! I understand about lasers and this is one of the reasons I chose to talk about the light loss in this way. Your description seemed to be saying originally that light reduced due to distance which would mean that the power of a laser would reduce in the same way. My explanation is sound for the macro tube which is what I was explaining!

cowasaki

31-12-2007, 14:30

It is quite clear from my diagram that I understand this principal. I just chose to explain it in a manner that I thought people might understand more easily. People getting hung up on whether it is because of distance or magnification is not really relevant in this simple example as both are inextricably linked. As long as it is clear there is a light loss due to distance OR magnification does not matter either - there is a light loss and it is proportional to EITHER as they are both linked. The diagram shows how the tubes work. :bonk::bonk:

TheWolf

31-12-2007, 14:36

Sorry for being a n00b, but how do you blurr the side? ^^

cowasaki

31-12-2007, 14:43

Sorry for being a n00b, but how do you blurr the side? ^^

If you are referring to the sides of the macro shot it is due to the depth of field. As you increase the f number you increase the amount of the picture that is in focus. As you decrease the f number you reduce the amount that is in focus. With macro shots this can make a big difference. I have been taking lots of jewellery shots as my wife makes it. If I have too low an f number then half a ring can be in focus and half not!

michaelho

31-12-2007, 14:49

yep, the lower the F number the bigger the aperture but the shallower the depth of field.
However in this shot I used extension tubes, when using extension tubes you can focus more closely in on the subject but the depth of field becomes very shallow. It's a lot easier to make things blur than to get things in focus.
I think I shot this with a f/8 value.

pxl8

31-12-2007, 14:54

I just chose to explain it in a manner that I thought people might understand more easily. People getting hung up on whether it is because of distance or magnification is not really relevant in this simple example as both are inextricably linked.

They're linked but that doesn't mean the light loss is due to the magnification.

Increased Distance = Magnifcation & Light Loss

You can't say that Increased Magnification = Light Loss because that simply isn't true. The same thing that causes the increase in magnification ALSO causes the light loss.

Apart from anything else in order to calculate the light loss you need to know the distance of extension. If you wanted to calculate it from the amount of magnification you'd still have to work out the extension in order to use the inverse square law - which, as we all know by now, is based on DISTANCE :lol:

People getting hung up on whether it is because of distance or magnification is not really relevant in this simple example as both are inextricably linked

If you allow people to believe that then they'll want to know how much light loss there is based on the magnification, ie.

Q: If I use a 25mm tube on a 50mm lens which gives me 0.5x magnification how much light loss will there be?

A: Approx. 1 stop.

Q: If I used 50mm of tubes on a 100mm lens which also gives me 0.5x magnification how much light loss will there be?

A: Approx 2 stops.

Q: Why is the light loss different if the magnification is the same?

A: Because it's the simple explanation... :bonk:

michaelho

31-12-2007, 15:01

cowasaki

31-12-2007, 15:14

They're linked but that doesn't mean the light loss is due to the magnification.

Increased Distance = Magnifcation & Light Loss

You can't say that Increased Magnification = Light Loss because that simply isn't true. The same thing that causes the increase in magnification ALSO causes the light loss.

I have already explained this several times, but you could apply simple algebraic techniques to your equation and make any of the three items the principal of the equation! I was never trying to give a total explanation of the working of lenses, cameras, lasers, light etc etc just that there would be a loss equal to the square of the magnification! Just that.

Apart from anything else in order to calculate the light loss you need to know the distance of extension. If you wanted to calculate it from the amount of magnification you'd still have to work out the extension in order to use the inverse square law - which, as we all know by now, is based on DISTANCE :lol:

OR it can also be based on my calculation! ie 8x mag = 8x8 times light loss

If you allow people to believe that then they'll want to know how much light loss there is based on the magnification, ie.

Q: If I use a 25mm tube on a 50mm lens which gives me 0.5x magnification how much light loss will there be?

A: Approx. 1 stop.

Q: If I used 50mm of tubes on a 100mm lens which also gives me 0.5x magnification how much light loss will there be?

A: Approx 2 stops.

Q: Why is the light loss different if the magnification is the same?

A: Because it's the simple explanation... :bonk:

If we JUST look at magnification:

you have a macro tube on a 60mm lens giving a magnification of 8 then the light loss is 63/64ths.

you have a macro tube on a 105mm lens giving a magnification of 8 then the light loss is 63/64ths

(but these would be different tubes!)

I TOTALLY APPRECIATE WHAT YOU ARE SAYING (and you are not wrong either in your descriptions but...)!

I am not WRONG we could argue over which way of describing it is best and I would accept this quite happily. My explanation is sound for the example it was used for.

I have a high degree of understanding of physics but I wont pretend to say I am necessarily explaining it the best way - just the way that seems best to me! I was just trying to explain a simple thing using laymans terms without going into lots of detail and causing confusion! (which I think we have done now!)

cowasaki

31-12-2007, 15:17

I think cowasaki was just trying to explain things in simple terms and was just referring to a specific lens combo. I'm pretty sure he knows the law and how things work. I think there's no further benefit of carrying on this discussion really.

I agree completely. I have better things to do than go round and round in circles arguing the SAME THING. :wave:

At least anyone reading this will now understand that you get a light loss due to macro tubes and this depends on the length and/or magnification which was all that we were both saying.

pxl8

31-12-2007, 15:52

...just that there would be a loss equal to the square of the magnification! Just that.

The magnification of a 50mm lens with 25mm of tubes is 0.5x

The magnification of a 100mm lens of 50mm of tubes is also 0.5x

According to your formula the light loss for these would be the same when in fact it's one stop more for the 100mm lens.

:shrug:

Just for clarity

a 100mm lens with 25mm of tubes has a mag of 0.25x so accordingly it should have less light loss than the 50mm lens, again not so.

:shrug:

cowasaki

31-12-2007, 16:00

The magnification of a 50mm lens with 25mm of tubes is 0.5x

The magnification of a 100mm lens of 50mm of tubes is also 0.5x

According to your formula the light loss for these would be the same when in fact it's one stop more for the 100mm lens.

:shrug:

Just for clarity

a 100mm lens with 25mm of tubes has a mag of 0.25x so accordingly it should have less light loss than the 50mm lens, again not so.

:shrug:

I am talking about percentage light loss over what is there originally (on the same lens). I was bored with this arguement whilst it was still 1 page.

You can argue with yourself now I can't be bothered wasting any more time with this. I am sure the person who asked about them can see how they work and that lots of light is lost. You understand it and so do I so i'll leave it at that and unsubscribe from the thread! Your time is obviously worth less than mine!