M43 flexibility for Macro photography with Oly 60mm F2.8, extension tubes, raynox M-250 and MC-20 TC

John K wrote:

gardenersassistant wrote:

John K wrote:

junmoe62 wrote:

Regarding the diopter, I know that the theory says that you do not use light, but in practice, I always find myself having to adjust the power of the flashes up when I put it on.

Because the magnification changed and the field of view dropped, so there is less surface area reflecting light back into the camera and the flash had to fire longer to compensate. So there's no light loss due to the diopter, but the increase in mag will require more light to get a proper exposure. Happens with extension tubes (to a slightly greater extent), teleconverters, etc. Any time the mag goes up the exposure will have to change to compensate.

I'm wondering how just how large an effect you would expect this magnification-caused change in illumination requirement to be with a close-up lens. You say it happens to a slightly greater extent with extension tubes, teleconverters etc, so presumably that means that if you use a close-up lens and increase the magnification you would need to add almost as much light as if you had made the same change in magnification using extension tubes, teleconverters etc. Have I understood you correctly?

Extension tubes (and a teleconverter as well) move the lens further away from the image plane and as the image circle expands the intensity of the light drops. You don't get that same effect with a diopter. No matter how you increase the magnification there is going to be less surface area reflecting light back into the lens as the mag goes up, and it was the original reason for effective Fstops. Back in the stone age, when we used hand held light meters, you had to compensate for that drop in light by adding stops to the aperture value displayed in the meter (the meter assumes that you're shooting at infinity). Effective Fstops has since been hijacked to use in diffraction calculations but I think it's just a convenient way of dealing with the aperture getting further from the sensor as the mag goes up (as the distance between the aperture and sensor increases light has more room to diffract).

And presumably the etc includes macro lenses, for example the MPE-65?

It does, but one way to compensate for it is to get the light source closer to the subject. If you're using a macro twin flash that drop in reflected light off of the scene as the mag increases can be offset due the distance between the flash heads and the subject getting shorter. It's possible to increase the mag and yet keep the flash power the same and still get a good exposure simply because the flash, mounted to the end of the lens, is closer to the subject.

Thanks John, but my question was about close-up lenses (what you refer to as "diopters"). It was this: "presumably that means that if you use a close-up lens and increase the magnification you would need to add almost as much light as if you had made the same change in magnification using extension tubes, teleconverters etc. Have I understood you correctly?"

And my other question was whether the same would apply if you used a macro lens such as the MPE-65 rather than extension tubes or a teleconverter for that side of the comparison.

This all has to do with your statement that "Any time the mag goes up the exposure will have to change to compensate." This is an issue which my two questions are intended to help us explore.

gardenersassistant wrote:

John K wrote:

gardenersassistant wrote:

John K wrote:

junmoe62 wrote:

Regarding the diopter, I know that the theory says that you do not use light, but in practice, I always find myself having to adjust the power of the flashes up when I put it on.

Because the magnification changed and the field of view dropped, so there is less surface area reflecting light back into the camera and the flash had to fire longer to compensate. So there's no light loss due to the diopter, but the increase in mag will require more light to get a proper exposure. Happens with extension tubes (to a slightly greater extent), teleconverters, etc. Any time the mag goes up the exposure will have to change to compensate.

I'm wondering how just how large an effect you would expect this magnification-caused change in illumination requirement to be with a close-up lens. You say it happens to a slightly greater extent with extension tubes, teleconverters etc, so presumably that means that if you use a close-up lens and increase the magnification you would need to add almost as much light as if you had made the same change in magnification using extension tubes, teleconverters etc. Have I understood you correctly?

Extension tubes (and a teleconverter as well) move the lens further away from the image plane and as the image circle expands the intensity of the light drops. You don't get that same effect with a diopter. No matter how you increase the magnification there is going to be less surface area reflecting light back into the lens as the mag goes up, and it was the original reason for effective Fstops. Back in the stone age, when we used hand held light meters, you had to compensate for that drop in light by adding stops to the aperture value displayed in the meter (the meter assumes that you're shooting at infinity). Effective Fstops has since been hijacked to use in diffraction calculations but I think it's just a convenient way of dealing with the aperture getting further from the sensor as the mag goes up (as the distance between the aperture and sensor increases light has more room to diffract).

And presumably the etc includes macro lenses, for example the MPE-65?

It does, but one way to compensate for it is to get the light source closer to the subject. If you're using a macro twin flash that drop in reflected light off of the scene as the mag increases can be offset due the distance between the flash heads and the subject getting shorter. It's possible to increase the mag and yet keep the flash power the same and still get a good exposure simply because the flash, mounted to the end of the lens, is closer to the subject.

Thanks John, but my question was about close-up lenses (what you refer to as "diopters"). It was this: "presumably that means that if you use a close-up lens and increase the magnification you would need to add almost as much light as if you had made the same change in magnification using extension tubes, teleconverters etc. Have I understood you correctly?"

Key word is "almost". A teleconverter and extension tubes move the lens further away from the image plane, and as the light expands the intensity will drop. You don't get that effect with a closeup lens.

And my other question was whether the same would apply if you used a macro lens such as the MPE-65 rather than extension tubes or a teleconverter for that side of the comparison.

If you're gonna set up some sort of side by side comparison and attempt to slice my throat go ahead. Just keep in mind that there will be differences in the physical size of the aperture, and potential differences in the distance between it and the image plane. I can only tell you that as the mag goes up, no matter how, the intensity of the light will drop due to the decrease in surface area reflecting light back into the lens.

This all has to do with your statement that "Any time the mag goes up the exposure will have to change to compensate." This is an issue which my two questions are intended to help us explore.

OK.

John K wrote:

pannumon wrote:

This is basic equivalence, you shoot f/8, 1/500s, ISO 400 on µ4/3 camera, or you can shoot f/16, 1/500s, ISO 1600 on FF camera. The same depth of field, same shutter speed, same amount of quantum (light) noise. There is no benefit from using the smaller sensor (except lower relative read noise and slightly better IQ), but on the other hand there is no benefit of using the larger sensor either.

It all comes to pixel density (more megapixels on the subject).

You touched on something that has seriously puzzled me, and I'm not trying to argue with you I'm actually interested in learning something.

A lot of people treat digital sensors like they are solar cells, and calculate exposure based on surface area. But a digital sensor is not a single piece of light sensitive silicon like a solar cell, it's made up of millions of light gathering pixels. So why would the exposure change between shooting full frame and a crop factor sensor when the intensity of the light falling on the individual pixels is the same?

If I had the money I would buy two 5ds cameras and using gaffers tape I'd tape off one of the sensors to make it a 1.6x crop camera and see if the exposure between it and the full frame version is different when shooting a 33% grey card.

I just did something rather similar, shooting a sheet of printer paper twice with my A7ii using aperture priority mode, one with APS-C mode off and one with it on, and no other changes. The exposure was the same.

gardenersassistant wrote:

John K wrote:

pannumon wrote:

This is basic equivalence, you shoot f/8, 1/500s, ISO 400 on µ4/3 camera, or you can shoot f/16, 1/500s, ISO 1600 on FF camera. The same depth of field, same shutter speed, same amount of quantum (light) noise. There is no benefit from using the smaller sensor (except lower relative read noise and slightly better IQ), but on the other hand there is no benefit of using the larger sensor either.

It all comes to pixel density (more megapixels on the subject).

You touched on something that has seriously puzzled me, and I'm not trying to argue with you I'm actually interested in learning something.

A lot of people treat digital sensors like they are solar cells, and calculate exposure based on surface area. But a digital sensor is not a single piece of light sensitive silicon like a solar cell, it's made up of millions of light gathering pixels. So why would the exposure change between shooting full frame and a crop factor sensor when the intensity of the light falling on the individual pixels is the same?

If I had the money I would buy two 5ds cameras and using gaffers tape I'd tape off one of the sensors to make it a 1.6x crop camera and see if the exposure between it and the full frame version is different when shooting a 33% grey card.

I just did something rather similar, shooting a sheet of printer paper twice with my A7ii using aperture priority mode, one with APS-C mode off and one with it on, and no other changes. The exposure was the same.

Which makes perfect sense -thanks Nick!

John K wrote:

gardenersassistant wrote:

John K wrote:

gardenersassistant wrote:

John K wrote:

junmoe62 wrote:

Regarding the diopter, I know that the theory says that you do not use light, but in practice, I always find myself having to adjust the power of the flashes up when I put it on.

Because the magnification changed and the field of view dropped, so there is less surface area reflecting light back into the camera and the flash had to fire longer to compensate. So there's no light loss due to the diopter, but the increase in mag will require more light to get a proper exposure. Happens with extension tubes (to a slightly greater extent), teleconverters, etc. Any time the mag goes up the exposure will have to change to compensate.

I'm wondering how just how large an effect you would expect this magnification-caused change in illumination requirement to be with a close-up lens. You say it happens to a slightly greater extent with extension tubes, teleconverters etc, so presumably that means that if you use a close-up lens and increase the magnification you would need to add almost as much light as if you had made the same change in magnification using extension tubes, teleconverters etc. Have I understood you correctly?

Extension tubes (and a teleconverter as well) move the lens further away from the image plane and as the image circle expands the intensity of the light drops. You don't get that same effect with a diopter. No matter how you increase the magnification there is going to be less surface area reflecting light back into the lens as the mag goes up, and it was the original reason for effective Fstops. Back in the stone age, when we used hand held light meters, you had to compensate for that drop in light by adding stops to the aperture value displayed in the meter (the meter assumes that you're shooting at infinity). Effective Fstops has since been hijacked to use in diffraction calculations but I think it's just a convenient way of dealing with the aperture getting further from the sensor as the mag goes up (as the distance between the aperture and sensor increases light has more room to diffract).

And presumably the etc includes macro lenses, for example the MPE-65?

It does, but one way to compensate for it is to get the light source closer to the subject. If you're using a macro twin flash that drop in reflected light off of the scene as the mag increases can be offset due the distance between the flash heads and the subject getting shorter. It's possible to increase the mag and yet keep the flash power the same and still get a good exposure simply because the flash, mounted to the end of the lens, is closer to the subject.

Thanks John, but my question was about close-up lenses (what you refer to as "diopters"). It was this: "presumably that means that if you use a close-up lens and increase the magnification you would need to add almost as much light as if you had made the same change in magnification using extension tubes, teleconverters etc. Have I understood you correctly?"

Key word is "almost". A teleconverter and extension tubes move the lens further away from the image plane, and as the light expands the intensity will drop. You don't get that effect with a closeup lens.

And my other question was whether the same would apply if you used a macro lens such as the MPE-65 rather than extension tubes or a teleconverter for that side of the comparison.

If you're gonna set up some sort of side by side comparison and attempt to slice my throat go ahead. Just keep in mind that there will be differences in the physical size of the aperture, and potential differences in the distance between it and the image plane. I can only tell you that as the mag goes up, no matter how, the intensity of the light will drop due to the decrease in surface area reflecting light back into the lens.

That is the core issue for me - you say that increased magnification reduces the light intensity reaching the sensor, however that magnification is achieved. However, this seems inconsistent with my experience with close-up lenses; when I change the magnification I don't have to change the flash power (I use a manual flash, so I think I would notice it if anything other than a small difference was going on).

Puzzled about this, I did an experiment, using as an example the difference in light intensity as between a magnification of 1:1 and 4:1, first with an MPE-65. I used it on a Panasonic G9. in aperture priority mode, using available light, I shot it at 1:1 and 4:1 with the same f-number and ISO for both shots.

Based on the effective f-numbers for these magnifications, I calculated an expected difference of light intensity of around 2.5 stops. The illustration below shows this was about right. The camera chose 1/50 sec for the 1:1 shot and 1/10 sec for the 4:1 shot. This is a difference of 2 and 1/3 stops, and the 4:1 shot is slightly darker. So this result is consistent with a difference in light intensity of around 2.5 stops.

Click on Original size beneath the image to see the animation.

With the same camera and subject, I then captured two images using a Raynox MSN-202 close-up lens on a 45-175 lens, one using 45mm and one using 175mm. This gave magnifications very similar to the ones with the MPE-65, 1.15:1 and 4:1. Here too I used aperture priority mode, using available light, with the same f-number and ISO for both shots.

The following illustration shows that the camera chose the same shutter speed for both shots, and the lightness of the two images was very similar. This means that the light intensity was pretty much the same at the two magnifications.

Click on Original size beneath the image to see the animation.

This seems to me to confirm my impression from shooting flash - if changing magnification when using close-up lenses does alter the light intensity reaching the sensor, then it doesn't change it by much.

There is a bit of a twist to this. I did similar comparisons with other close-up lenses (Raynox 150 and 250, Canon 500D, Marumi 200 and two Marumi 330s, one reversed on the other), shooting pairs of shots at 45mm and 175mm as I had for the Raynox 202.

These pairs all gave the same result, which was that the camera chose the same shutter speed for both shots in the pair, and the lightness of the shots in each pair was almost the same, but they differed very slightly, and differed in the same way for every pair. Here is the Raynox 202 comparison again, but this time with the histograms aligned.

Click on Original size beneath the image to see the animation.

We can see that the 4:1 shot was very slightly darker than the 1.15:1 shot.It is a very small difference. For example, thinking back to the MPE-65 example, the illustration below shows what a 2 and 1/3 stop difference looks like on those histograms.

Click on Original size beneath the image to see the animation.

The difference we are seeing with the close-up lenses is tiny compared to that. (Presumably it is less than 1/3 stop otherwise the camera would have changed the shutter speed to keep to the required exposure compensation.)

I wondered if this might have something to do with the design of the 45-175, which does not extend as you increase focal length. However I get the same effect with a 45-200, which does extend.

Curious. I wonder what is causing this.

gardenersassistant wrote:

I wondered if this might have something to do with the design of the 45-175, which does not extend as you increase focal length. However I get the same effect with a 45-200, which does extend.

Curious. I wonder what is causing this.

Your post is the reason why I have a tendency not speak in absolutes (except that cropping doesn't change the mag ). Gonna be tough to wrap my head around your results cause there are too many variables.

gardenersassistant wrote:

If you're gonna set up some sort of side by side comparison and attempt to slice my throat go ahead. Just keep in mind that there will be differences in the physical size of the aperture, and potential differences in the distance between it and the image plane. I can only tell you that as the mag goes up, no matter how, the intensity of the light will drop due to the decrease in surface area reflecting light back into the lens.

That is the core issue for me - you say that increased magnification reduces the light intensity reaching the sensor, however that magnification is achieved.

Should have said "when modifying the mag of the same lens". once you start comparing different lenses, especially the MP-E which has a very unique design, then you're going to run into some odd results.

However, this seems inconsistent with my experience with close-up lenses; when I change the magnification I don't have to change the flash power (I use a manual flash, so I think I would notice it if anything other than a small difference was going on).

Puzzled about this, I did an experiment, using as an example the difference in light intensity as between a magnification of 1:1 and 4:1, first with an MPE-65. I used it on a Panasonic G9. in aperture priority mode, using available light, I shot it at 1:1 and 4:1 with the same f-number and ISO for both shots.

Based on the effective f-numbers for these magnifications, I calculated an expected difference of light intensity of around 2.5 stops. The illustration below shows this was about right. The camera chose 1/50 sec for the 1:1 shot and 1/10 sec for the 4:1 shot. This is a difference of 2 and 1/3 stops, and the 4:1 shot is slightly darker. So this result is consistent with a difference in light intensity of around 2.5 stops.

Which makes perfect sense due to the surface area changing as the mag changed. But still not the jump I'd expect when looking at the effective aperture chart in the MP-E Manual

Click on Original size beneath the image to see the animation.

John K wrote:

gardenersassistant wrote:

If you're gonna set up some sort of side by side comparison and attempt to slice my throat go ahead. Just keep in mind that there will be differences in the physical size of the aperture, and potential differences in the distance between it and the image plane. I can only tell you that as the mag goes up, no matter how, the intensity of the light will drop due to the decrease in surface area reflecting light back into the lens.

That is the core issue for me - you say that increased magnification reduces the light intensity reaching the sensor, however that magnification is achieved.

Should have said "when modifying the mag of the same lens". once you start comparing different lenses, especially the MP-E which has a very unique design, then you're going to run into some odd results.

The Raynox 202 example was modifying the magnification of the same lens. It is the Raynox 202 example, by itself and without reference to the MPE-65, which shows that magnification can change without significantly altering the light intensity reaching the sensor. This is a counterexample to your "as the mag goes up, no matter how, the intensity of the light will drop".

I included the MPE-65 example to show how big the difference in light intensity hitting the sensor is [EDIT when not using a close-up lens] as magnification changes. This was to show the extent of the difference which would be needed for a close-up lens for it to be to almost as large as with the MPE-65 (or extension tubes, or a teleconverter), which you said was the case.

The MPE-65 results are not at all odd (see below). It produces exactly the effective apertures one would expect at different magnifications, and hence exactly the difference in light intensity hitting the sensor as one could expect as between two particular magnifications, such as in this case 1:1 and 4:1.

However, this seems inconsistent with my experience with close-up lenses; when I change the magnification I don't have to change the flash power (I use a manual flash, so I think I would notice it if anything other than a small difference was going on).

Puzzled about this, I did an experiment, using as an example the difference in light intensity as between a magnification of 1:1 and 4:1, first with an MPE-65. I used it on a Panasonic G9. in aperture priority mode, using available light, I shot it at 1:1 and 4:1 with the same f-number and ISO for both shots.

Based on the effective f-numbers for these magnifications, I calculated an expected difference of light intensity of around 2.5 stops. The illustration below shows this was about right. The camera chose 1/50 sec for the 1:1 shot and 1/10 sec for the 4:1 shot. This is a difference of 2 and 1/3 stops, and the 4:1 shot is slightly darker. So this result is consistent with a difference in light intensity of around 2.5 stops.

Which makes perfect sense due to the surface area changing as the mag changed. But still not the jump I'd expect when looking at the effective aperture chart in the MP-E Manual

The effective f-numbers the manual gives are exactly the same as those I calculated (f/22 and f/55).

MPE-Manual

My calculations

f/44 is two stops from f/22, and f/54 is 1/2 stop from f/44, total 2 1/2 stops.

Click on Original size beneath the image to see the animation.

John K wrote:

gardenersassistant wrote:

I wondered if this might have something to do with the design of the 45-175, which does not extend as you increase focal length. However I get the same effect with a 45-200, which does extend.

Curious. I wonder what is causing this.

Your post is the reason why I have a tendency not speak in absolutes (except that cropping doesn't change the mag ).

Not at the sensor, no.

Gonna be tough to wrap my head around your results cause there are too many variables.

Which of the variables are you having difficulty with? As far as I can see, for the counterexample I provided (the Raynox 202 at 1:1 and 4;1, see my response to your other comment) there are only two variables. Apart from the magnification and the shutter speed (and possibly also the focal length if you want to separate it out from the magnification, which it drives), the other variables were held constant (same camera, same subject, same camera and subject positions, same lens arrangement, same distance to subject, same subject illumination, same aperture, same ISO).

pannumon wrote:

John K wrote:

pannumon wrote:

This is basic equivalence, you shoot f/8, 1/500s, ISO 400 on µ4/3 camera, or you can shoot f/16, 1/500s, ISO 1600 on FF camera. The same depth of field, same shutter speed, same amount of quantum (light) noise. There is no benefit from using the smaller sensor (except lower relative read noise and slightly better IQ), but on the other hand there is no benefit of using the larger sensor either.

It all comes to pixel density (more megapixels on the subject).

You touched on something that has seriously puzzled me, and I'm not trying to argue with you I'm actually interested in learning something.

Fair enough.

A lot of people treat digital sensors like they are solar cells, and calculate exposure based on surface area.

A lot of people are wrong. The unit of exposure is per area (not per sensor area), meaning light intensity, not the total amount of light that is hitting the sensor. The total amount of light hitting the sensor is exposure multiplied by sensor area. Exposure determines the ISO value and brightness, total amount of light determines the level of noise (per photo, not per pixel).

But a digital sensor is not a single piece of light sensitive silicon like a solar cell, it's made up of millions of light gathering pixels. So why would the exposure change between shooting full frame and a crop factor sensor when the intensity of the light falling on the individual pixels is the same?

Sensor size or crop factor does not affect the exposure. If I somewhere wrote so, I was wrong (but I think I did not).

That's what is sounded like when you were comparing exposures between FF and crop sensors above.

The same exposure at larger sensor in principle gives less noise and shallower depth-of-field.

Now I'm puzzled again. How does sensor size change depth, when depth is strictly a function of Fstop and magnification. Are you trying to maintain the same relative subject size in the frame that you'd have on a crop sensor? If so the magnification of the scene projected onto the FF sensor has gone up, and it's the increase in mag that has dropped the depth and not some inherent property of the sensor.

A 1x macro lens set to minimum focus on a camera set to F11 (just for example) will give you exactly the same depth of field no matter what camera body that lens is attached to. The only thing that will change is the size of the subject in the resulting image due to smaller than full frame sensors cropping the image circle. I think the confusion comes in when people multiply the crop of their sensor by the magnification that the lens is giving them. But the crop that you get from a crop factor sensor is functionally the same as cropping in post. Cropping an image will never change the magnification, no matter where or how it's done. This whole issue was EXTREMELY painful in the APS-C community about a decade ago. Took a long time for people to realize that crop factor sensors didn't re-write all the rules of photography or defy physics, and it's jut a crop.

In order to compensate the depth-of-field, on a larger sensor a smaller aperture needs to be used (f/16 instead of f/8 in the example). The exposure is now different, but the total amount of light absorbed by the sensor is the same (as is depth-of-field). This is why we can expect similar noise performance. This is equivalence.

OK, I think you're trying to maintain the same subject size in the frame. Gotta get out of the mentality that subject size matters, and you could keep the subject the same size in both images just by cropping the full frame one.

Equivalence is a very volatile topic, but there are hundreds if not thousands of threads about it (no need to repeat all that).

Let's not, cause it's a really bogus topic / metric. Just crop the full frame image and you're done.

In my opinion the main problem is that many people confuse total light gathered by sensor (for example watts or quanta) with light intensity [light gathered by let's say 1 m^2 (watts or quanta per one square meter) or 1 cm^2 (watts or quanta per one square centimeter) of sensor].

I always think of it in terms of light gathered by each individual pixels because that's how sensors work.

I want to add to my previous message that larger sensor has a benefit when shooting at low ISO (base ISO). Larger sensor can be better for macro photography.

What benefit exactly? IMHO a crop factor sensor is better because it's easier to fill the frame with the subject at lower magnifications, and lower mag = more depth of field. I've invested so much time in learning how to control where that depth falls in the frame that I have no interest in focus stacking. One frame, hand held, F11 and just under 2x (at the sensor -sucks that I have to say that it should be obvious cause cropping does not equal magnification).

Tech Specs: Canon 80D (F11, 1/250, ISO 200) + a Canon MP-E 65mm macro lens (set to roughly 2x) + a diffused MT-26EX RT (E-TTL metering).

To get the same framing with a FF sensor I'd either have to crop the photo (and I don't crop in post), or shoot at a higher mag and either take a hit in depth or drop the lens down to F16 (max aperture) and take a diffraction hit. Would also take a hit in IQ because the MP-E isn't as sharp at F16 as it is at lower apertures (there's a difference that can't be explained by diffraction since sharpness improves at F14). So not sure what I'd gain going full frame other than a little more dynamic range and a little less noise (both of which are a non issue with Canon's 80D).

gardenersassistant wrote:

John K wrote:

gardenersassistant wrote:

If you're gonna set up some sort of side by side comparison and attempt to slice my throat go ahead. Just keep in mind that there will be differences in the physical size of the aperture, and potential differences in the distance between it and the image plane. I can only tell you that as the mag goes up, no matter how, the intensity of the light will drop due to the decrease in surface area reflecting light back into the lens.

That is the core issue for me - you say that increased magnification reduces the light intensity reaching the sensor, however that magnification is achieved.

Should have said "when modifying the mag of the same lens". once you start comparing different lenses, especially the MP-E which has a very unique design, then you're going to run into some odd results.

The Raynox 202 example was modifying the magnification of the same lens. It is the Raynox 202 example, by itself and without reference to the MPE-65, which shows that magnification can change without significantly altering the light intensity reaching the sensor. This is a counterexample to your "as the mag goes up, no matter how, the intensity of the light will drop".

But it did change Nick. Not exactly sure what you're looking for here. Do I need to mail you a T-shirt that says "John K was Wrong"? Refer back to my previous comment about you setting up some test and then slicing my throat...

I included the MPE-65 example to show how big the difference in light intensity hitting the sensor is [EDIT when not using a close-up lens] as magnification changes. This was to show the extent of the difference which would be needed for a close-up lens for it to be to almost as large as with the MPE-65 (or extension tubes, or a teleconverter), which you said was the case.

With the MP-E the mag went up by a factor of 4 (4 times higher). What was the mag difference with the 202?

The MPE-65 results are not at all odd (see below). It produces exactly the effective apertures one would expect at different magnifications, and hence exactly the difference in light intensity hitting the sensor as one could expect as between two particular magnifications, such as in this case 1:1 and 4:1.

2.5 stops didn't seem like that big of a difference to me -I actually expected it to be higher.

John K wrote:

gardenersassistant wrote:

John K wrote:

gardenersassistant wrote:

If you're gonna set up some sort of side by side comparison and attempt to slice my throat go ahead. Just keep in mind that there will be differences in the physical size of the aperture, and potential differences in the distance between it and the image plane. I can only tell you that as the mag goes up, no matter how, the intensity of the light will drop due to the decrease in surface area reflecting light back into the lens.

That is the core issue for me - you say that increased magnification reduces the light intensity reaching the sensor, however that magnification is achieved.

Should have said "when modifying the mag of the same lens". once you start comparing different lenses, especially the MP-E which has a very unique design, then you're going to run into some odd results.

The Raynox 202 example was modifying the magnification of the same lens. It is the Raynox 202 example, by itself and without reference to the MPE-65, which shows that magnification can change without significantly altering the light intensity reaching the sensor. This is a counterexample to your "as the mag goes up, no matter how, the intensity of the light will drop".

But it did change Nick.

It, being the light intensity falling on the sensor, did change, as expected, with the MPE-65. It changed very slightly with the 202. It turns out though that that change has nothing to do with using a close-up lens or magnification. I just got the same effect by pointing the 45-175 (with no close-up lens) at a clear sky, focused at infinity - at 175mm it had the same slight drop in lightness compared to 45mm as with my tests with close-up lenses. Therefore, the close up lenses caused no drop in lightness; it did not change.

Not exactly sure what you're looking for here. Do I need to mail you a T-shirt that says "John K was Wrong"? Refer back to my previous comment about you setting up some test and then slicing my throat...

I included the MPE-65 example to show how big the difference in light intensity hitting the sensor is [EDIT when not using a close-up lens] as magnification changes. This was to show the extent of the difference which would be needed for a close-up lens for it to be to almost as large as with the MPE-65 (or extension tubes, or a teleconverter), which you said was the case.

With the MP-E the mag went up by a factor of 4 (4 times higher). What was the mag difference with the 202?

Within the margins of measurement error the magnification difference was the same in both cases, 4X, and, importantly, it was between the same two magnifications in both cases, 1X and 4X. (There is some approximation in both cases - approximation in measuring the scene widths for the 202 to work out the magnification, and approximation in whether I exactly hit the magnification markings on the MPE-65.)

The MPE-65 results are not at all odd (see below). It produces exactly the effective apertures one would expect at different magnifications, and hence exactly the difference in light intensity hitting the sensor as one could expect as between two particular magnifications, such as in this case 1:1 and 4:1.

2.5 stops didn't seem like that big of a difference to me -I actually expected it to be higher.