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

Thank you, I have Wemacro and Stackshot rails/controllers , use Oly and Nikon microscope  finite & infinite objectives... great for any magnification over 5x.

John K wrote:

pannumon wrote:

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.

Depth of field is defined by circle of confusion. It is different for different image sizes and viewing conditions, such as viewing distances.

The DoF is the same for APC-S and FF as long as the images are not magnified after capture, or as long as they have the same magnification (not to be confused with with magnification of the objective). This means that we would have two images next to each other, the subject in both photo would look equally big, but the image would have cropped borders and it would be smaller (smaller frame).

Now if we want the images to be the same size we need to magnify the smaller image so that frame size is the same as the FF image, we decrease the DoF. Some parts of the image that on FF version look sharp now look blurry on APS-C version, because we can now see it's not sharp.

I think the key here is that magnification happens two times, first when the image is captures, and second when the image is viewed. The amount of magnification needed for viewing depends on the sensor size.

Personally, I have had hard time getting this.

Are you trying to maintain the same relative subject size in the frame that you'd have on a crop sensor?

No.

Unfortunately I am more busy (not because of work luckily) than I expected, so I have to leave it here for the weekend at least. It is a shame because you have good input I cannot analyze now.

John K wrote:

pannumon wrote:

John K wrote:

pannumon wrote:

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.

Depth of field is defined by circle of confusion. It is different for different image sizes and viewing conditions, such as viewing distances.

Depth of field really does not change after the shutter is pressed. You might think that there is more depth in an image depending on the size that you view a photo, but in reality the depth is fixed.

Please check the definition of depth of field and circle of confusion. Convince Wikipedia that their article is wrong.

pannumon wrote:

John K wrote:

pannumon wrote:

John K wrote:

pannumon wrote:

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.

Depth of field is defined by circle of confusion. It is different for different image sizes and viewing conditions, such as viewing distances.

Depth of field really does not change after the shutter is pressed. You might think that there is more depth in an image depending on the size that you view a photo, but in reality the depth is fixed.

Please check the definition of depth of field and circle of confusion. Convince Wikipedia that their article is wrong.

@pannumon
I agree with you.
The trap many fall into is assuming DoF is a physical dimension. It's not. It's a subjective quality of someone with normal eyesight viewing an image hanging on a wall from a certain distance. People have tried to quantify this with the subjective concept of circle of confusion, a reasonable thing to do. To deal with it, they have then put mathematics around it, again a reasonable thing to do. Unfortunately, this then provides a mathematical point where it might be said that on one side it's in focus and on the other side it's out of focus, which is of course rubbish but it's useful guiding tool in photography if properly understood.
When arguing over DoF, one really aught to leave all preconceived ideas aside and say, "You print and image, I'll print an image. We'll hang them on a wall side by side, then we'll talk DoF."

John K wrote:

No need, because depth of field can be calculated but it's also perception based. Take a look at the Canon MP-E 65mm manual , specifically the depth of field chart. No where does it mention anything about reproduction ratios and that's because it doesn't matter how large you view the print. The depth is fixed at the time of exposure. Any change in depth after that is perceived and not actual.

In order to calculate depth of field, the acceptable size of circle of confusion needs to be determined. This depends heavily on final size and viewing distance of the photo. This is a factual statement, not a matter of an opinion.

For example, see https://en.m.wikipedia.org/wiki/Depth_of_field

Canon may simplify things in their manual, but that does not change the facts. You may define "depth" as you like, but depth of field is already defined, although you may not like the definition.

As I said, I have have a hard time with this, but now I see.

Moggi1964 wrote:

WOW! just doesn't cut it but swearing isn't allowed.

You are both incredibly talented and thank you for sharing your images.

Oh, and welcome Julien.

Amen! These images are incredibly good. I love that all the bugs are in what looks like their natural environment.

Great shots!  I haven't had the patience to get into stacking.

Had thought about trying the 1.4x with an extension tube, but hadn't tried it yet (don't have the 2x yet)

Another thing to try is use the OM bellows with a modified extension tube (split apart then connect the two parts w a ribbon cable and mount on either side of the bellows)  Ive seen that done here, but haven't tried it myself

gardenersassistant wrote:

pannumon wrote:

John K wrote:

No need, because depth of field can be calculated but it's also perception based. Take a look at the Canon MP-E 65mm manual , specifically the depth of field chart. No where does it mention anything about reproduction ratios and that's because it doesn't matter how large you view the print. The depth is fixed at the time of exposure. Any change in depth after that is perceived and not actual.

In order to calculate depth of field, the acceptable size of circle of confusion needs to be determined. This depends heavily on final size and viewing distance of the photo. This is a factual statement, not a matter of an opinion.

For example, see https://en.m.wikipedia.org/wiki/Depth_of_field

Canon may simplify things in their manual, but that does not change the facts. You may define "depth" as you like, but depth of field is already defined, although you may not like the definition.

As I said, I have have a hard time with this, but now I see.

Doesn't this extended argument come down essentially to John believing that what matters is the magnification on to the sensor, and you believing that what matters is an image as viewed, which depends on enlargement in addition to the magnification?

Seems to me that both ways of looking at it have their uses, depending on the context, rather than one or other of them being the ... uniquely correct/valid/useful/appropriate way of looking at it.

Actually the question was whether smaller sensors provide benefits for macro photography over larger ones. It would be nice if everybody could be right, but as I wrote this is not a matter of opinion. Anyway thanks for being diplomatic.

John K wrote:

junmoe62 wrote:

John K wrote:

junmoe62 wrote:

So, let me ask you a question. I definitely don’t want to get into all the equivalence controversy thing, because I have not much interest in all that stuff, and I most of the time have better things to do, but I’m interested in your view on that. My question is : Do you think it is totally unacceptable to say, for example, a 300mm F4 on a m43 body is roughly equivalent to a 600mm F8 on FF body?

It's the same, but only in the sense that the field of view will be the same. But if the focal length actually changed then there would also be a change in perspective. As you go from a wider angle to a narrower one objects in the scene start to appear closer together. That perspective change doesn't happen when you crop a photo, no matter how or when the crop is done.

Well John, I’m afraid to tell you that this time you are the one guilty of spreading misinformation!

If anything I'm guilty of over simplifying it, but you took care of that below:

Hi john,

After reading your message again, I’m not entirely sure what you actually meant or what point you where trying to make. So I’ll give you the benefit of the doubt and let you develop a little more if you wish to.

But to me it sounds a whole lot like you were saying that because the 300mm lens on m43 is a wider focal length than the 600mm on FF, the framing would be the same, but the perspective would be different. This is totally wrong and no amount of over simplification will ever make this right. From the same distance to subject, so putting both setups on the same tripod, focusing on the same subject, the 300mm @F4 on m43 and the 600mm @F8 should give you the same framing, same perspective and same perceived DOF on the picture.

Saying, and I quote you : “As you go from a wider angle to a narrower one objects in the scene start to appear closer together” this is totally wrong. If you do no move your position relative to your subject to keep this subject the same size relative to the framing, the perspective won’t change at all.

To me this is actually quite a big mistake, because it’s directly affecting one the most important aspect of photography, which is composition.

Now to be perfectly honest, I personally don’t mind much, because as I stated before, I’m not much of a tech guy, and I prefer put my focus on the real world practical experience than the actual scientific and physics aspect of photography. You are the one who seem to be very attached to the semantics and accurate phrasing, so I though it would only be fair if it applied to you as well.

I mean, nowadays with digital cameras you can see instantly what you’re getting, so generally you’ll make test shots before committing to your final shot. I can imagine in the old times it was paramount to know all the intricacies of the physics, because you didn’t have the flexibility that we have today, and you couldn’t afford any mistakes. But nowadays, IMHO I don’t feel that it is of such great importance. Is it good to know about all the physics involved? Yeah, sure! It’s better if you know it all. It probably could help you figure out things a bit faster, but is it the end all be all? I don’t think so! Especially when you consider that all those theories apply in a perfect world. In the real world, so many parameters are involved that it is almost never 100% accurate.

The focal length of a lens alone has absolutely no effect on the perspective! Your position relative to the subject does. You can experiment yourself by taking a picture of a subject from the same position with a zoom lens on your camera. Take a picture at the widest angle you can, then zoom to the max and repeat. You will see that the perspective of the zoomed picture will match the one from the same location on your wide angle shot (minus the potential optical flaws like lens distortions (pinch, barrel and so on) obviously).

So when you zoom with your lens, you basically “cropping” the framing... and I’m not counting DOF and other aspects.

Which means, if you take a picture of the same subject, from the same location with a 300mm on m43 and a 600mm on FF, you should have the exact same framing and perspective. You just cropped, and crop doesn’t affect perspective...

I just googled the first article talking about that to link for you as a reference, in case my words are not enough to convince you :

https://martinbaileyphotography.com/2017/04/10/the-effect-of-subject-distance-and-focal-length-on-perspective-podcast-568/

That pretty much sums up why 800mm on m43 isn't the same as 800mm on a full frame camera. Let me try this from another angle:

Well... a 800mm lens is a 800mm lens and this is not dependent upon the sensor size. The sensor size will only change the resulting framing provided by those lenses.

If I shot with a full frame sensor using a 300mm lens, cropped the resulting images in post to a 2x crop factor, and claimed that the resulting photos were shot with a "600mm virtual lens" you'd call me nuts.

I would personally not call you nuts for saying that. If you understand that the fact of cropping 2x will reduce you picture‘s resolution by the same amount. The resulting framing of your cropped picture would be similar to what you would get with a 600mm lens. You would obviously lose 2x the resolution compared to shooting with a real physical 600mm lens and also emphasize the flaws of the lens.

Cropping in post doesn't change the focal length that the image was taken with. But since cropping in post, and cropping a full frame image circle with a smaller than full frame lens, is functionally the same then the focal length doesn't change no matter what camera body you use. When you crop an image, no matter how you do it, the only thing that changes is the field of view and how large the subject looks in the frame. This is great time to use terms like "full frame equivalent field of view".

Totally agree with you!

I remember these discussions in the APS-C community, and they were really painful. Way too many people wanted to think that the 1.6x crop was somehow magical, like the rules of photography and physics had to be rewritten to be re-written to explain the magic that was nothing more than a simple crop. Seems the m43 community isn't there yet, and I regret stepping in it...

If you think it is unacceptable, then fine!

Not unacceptable, but not the same. Sorry.

But if you think it is acceptable to some extent (like the vast majority on the internet), I could argue that following your thought process, from the same distance, which would translate to same framing, if you fill the frame with a ruler of 1 meter, the m43 system would give you a magnification of 17.3mm / 1000mm = 0.0173, while the FF system would give you 36mm / 1000mm = 0.036.

But you can't fill the frame with a ruler on both systems -the m43 is smaller. If you're saying that you are filling the frame on both then either the m43 is at a lower magnification (there's that word again ) or there's a difference in distance between the subject and the sensor with the ruler being closer to the full frame sensor. In either case the magnification isn't the same, if it were you'd only see half of the ruler in the m43 photo because the image is being cropped. At the same mag and Fstop depth of field will be the same for both sensors. But if you shoot at 1x with the full frame sensor, and shoot at .5x with the m43 but call it 1x due to the crop factor then the m43 image will have more depth because the mag is lower. That's the main reason why I think that cropping shouldn't be viewed as magnification, and why the two really are not the same.

In my example I was still talking about the 300mmF4 m43 lens VS the 600mmF8 FF lens. I though once again that it was obvious... sin

ce I precisely said “from the same distance, which would translate to same framing”.

My mistake.

Why wouldn’t I be able with those setups, from the same position and the ruler at the same distance, be able to fill the width of frame with the exact same 1 meter mark? Yet I believe the m43 would give a 0.0173x mag. while the FF would give 0.036x mag.

Is the 300mm m34 lens projecting a smaller image circle? Is so then it's focal length is probably a m43 equivalent (like the EF-S lenses for Canon APS-C camera bodies).

I have absolutely no idea!

So, since we saw above that FL has nothing to do with perspective if you shoot a subject from the same distance, and that the DOF from a F4 on m43 is very similar to a F8 on FF (btw, I’m still referring to the same lenses mentioned above, in case it wasn’t clear enough), don’t you think that feels very close, in the concept, to crop in post or with the sensor? Maybe the semantics are not of absolute perfection and accuracy, but honestly, that’s a good enough approximation for me.

Does that make the whole theory totally useless and cannot be used to have a rough idea of what to expect? I personally don’t think so, YMMV.

Yes it does invalidate it because of the differences in depth of field, diffraction softening, and I'm probably forgetting a few others. The problem is that you're assuming someone just getting into macro is going to know everything that you do, not realizing that juggling terminology could be confusing.

Well, honestly I don’t think this kind of tight and minute subtleties in the photography jargon is gonna appeal to, nor affect the photos of macro beginner!

I'd be pretty bummed if I got into m43 thinking that the 2x crop would actually give me more mag, and with it more detail, only to find out that it's just a crop.

Once again you’re theoretically right, but practically I think this is largely dependent on the optical qualities of the lenses and the pixel densities of the sensors.

Let’s stay in the theory and say we are in a perfect world (with Teletubies, rainbow unicorns and cotton candy clouds everywhere. My favorite place ever!! :D). We make a side by side comparison :

We shoot an optically perfect 60mm 1x mag lens @f2.8 on a perfect 20MP m43 sensor @ iso100

We shoot an optically perfect 120mm 1x mag lens @f5.6 on a perfect 20MP FF sensor @ iso400

both same technology, same subject and distance to subject.

So both systems are shooting at the same magnification, yet, which picture do you think will end up with the most details?

It is interesting when you read the Wikipedia definition of magnification :

quote from Wikipedia : “Magnification is the process of enlarging the apparent size, not physical size, of something. This enlargement is quantified by a calculated number also called "magnification". When this number is less than one, it refers to a reduction in size, sometimes called minification or de-magnification.

Typically, magnification is related to scaling up visuals or images to be able to see more detail, increasing resolution, using microscope, printingtechniques, or digital processing. In all cases, the magnification of the image does not change the perspective of the image.”

Based on that definition I see 2 interesting things :

- If Magnification is the process of enlarging the apparent size, not physical size, of something. Does it mean that enlarging the apparent size thanks to the pixel density of the sensor be considered as magnifying, even though the magnification of the lens relatif to the sensor size is a fixed number?

- We can also see from this definition that the magnification of the image does not change the perspective of the image. Which shows once again that zooming, magnifying or cropping doesn’t affect in anyway the perspective.

Look I'm not trying to bash you, the camera you use, or anything else. Putting anyone, or anything, down doesn't do me any good. I was just trying to clear up some important terminology.

I totally understood your attempt John, absolutely no offense has been taken. I also told you in each and every of my posts that I wholeheartedly agreed with you, that you are totally correct (Except for the perspective thing) and I even thanked you many times for correcting the mistakes. Nothing has changed and I truly mean it!

The only point I was trying to make since the beginning concernes the fact that I don’t think it is very helpful nor meaningful enough to hijack each and every threads and turn them into super geeky techy fight. I’m not implying that is what you do nor that is a habit of yours, but if you spent enough time in the m43 forum, you will see this kind of behavior is extremely common, to the point where it just becomes toxic. Everyone spending a minimum of their time in the m43 forum already witnessed that countless times I’m sure. One would be extremely unlucky (or should I say lucky :D) to miss on the equivalence talks in this forum!!!

I just think this kinds of endless boring talks just don’t really help anyone and actually Scare away many beginners and new comers. I know for a fact that it did for me for several years. And I can promise you that while writing this thread I was sure it will turn out that way!! I don’t know what’s going on on this forum, but if you have the very bad idea to associate the letter “E” and “Q” next to each others, a very strong chemical reaction will happen!! This thing is like nitroglycerine!! One drop is enough!! Boom!

I think spending more time on what’s actually going to improve the overall photographs (like lighting, composition, color science, how to approach the subject, how to get good diffusion and catchlights in the insects eyes,...) would be way more useful to everyone, especially beginners, than getting semantics right. Sadly you chose the latter... I mean, in all your posts in the thread you never ever referred once nor commented on the pictures, even though I invited people to do so in my original post and that I would have really been glad about it. For example, it’s my first time posting on the forum, do you think your 2 first posts sound like a warm welcoming to the forum?! It felt more like passing an exam, and the teacher correcting the mistakes. It was only missing the score at the end! I’m not really sure that’s what most people willing to post on the forum are after, but I might be wrong...

If you wanna believe that you're actually getting more magnification, more focal length, or even a better parking spot just because you're using a 2x crop factor sensor that's fine. I'll leave you to your echo chamber that seems to be the m43 community.

The thing is that I don’t think I’ve ever Implied that! For example, when I say “a 300mm F4 on a m43 body is roughly equivalent to a 600mm F8 on FF body“ I don’t think it means in anyway that a 300mm F4 on a m43 body is a 600mm F8 on FF body.

Anyways, in the end I think we are agree on the core thing, but we are just arguing about a different way of looking at things and we don’t put the cursor of the accuracy/approximation at the same level. You’re more on the tight & academic side, I’m more on the lose & field experience side... To illustrate my point I could see a talk between Mozart and Jimi Hendrix, with Mozart saying : “academic learning is key!!!” And Hendrix answering something like : “F@#$ that sh#$, bruh!!! Practice and experience is the answer!” :D.

To end this long answer, I really want to emphasize that I in no way attempted to bash you either and I really hope you won’t take anything personal. You sound like a very nice and knowledgeable guy and I really hope we’ll be able to have friendly and constructive talks in the future! I mean it! (I just hope it won’t be on equivalence though!!! :D)

I wish you a nice day and happy shooting.

Regards,

Julien

EM1Peter wrote:

Very impressive

I bought my 10mm extension tube quite a while ago when there wasn't much choice. I did try to attach the MC-20 to a 14-40 pro lens using the 10 mm extension tube shortly after it's delivery last year but the neck on the tube was marginally too narrow for the protrusion into the lens of the MC-20.

Searching a few minutes ago I found quite a range of extension tubes at an even bigger range of prices. Since there are no optics in these, there doesn't seem much point in paying more than necessary for the extension tube. Could you kindly advise the make of tube you are using.

Hi Peter,

Thank a lot for your kind words!

for the tubes, the LAINA and the PIXCO are the only one that I know of that will work.

I invite you to check the posts on the first page for the details on the setup

Many thanks

Peter

PS wouldn't it be nice if the proposed macro pro lens took the MC-20 as standard and maybe even additional IS stability in the lens?

Yes it would be awesome, especially if it is a 2:1 macro. If not, I’ll probably be a little disappointed because it won’t make a very big difference with what you can get with the 60mm F2.8 and the the tubes + TC hack. Still I would greatly welcome the additional working distance.

Cheers,

Julien

gardenersassistant wrote:

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.

Hi Nick,

That’s a very interesting experiment that you did there! Thanks for taking the time to do it.

Am I right in assuming that your working distance didn’t change during your test? By that I mean that your position relative to the subject didn’t change? If it is the case (At least regarding dioptres / magnifying glass), it would mean that increasing the magnification alone (without getting closer to the subject) doesn’t change exposure in a meaningful way. This result actually doesn’t look so surprising when you think about it. When you take a picture of a magnifying glass while still showing the surroundings, the area inside the magnifying glass doesn’t look darker (in a meaningful way).

Just for the sake of illustrating what I’m saying, here is a picture that was on the Wikipedia page for the definition of “magnification” :

Obviously, this picture doesn’t remotely represent any sort of scientific evidence.

One could probably argue that if the light source is positioned behind the magnifying glass, the latter could concentrate the light on te magnified area, I guess. But your experiment seemed quite accurate and couldn’t suffer from that “problem”.

Now though, I’m wondering if you would still get the same result when changing you working distance. Because that’s what’s happening when you add a diopter on a lens. So while using the bare lens at it’s closest focusing distance, do you still get the same exposure than when using that same lens + the diopter At the closest focusing distance?

If the exposure gets darker in the latter configuration, I guess my guts feeling that the inverse square law was partly responsible is probably closer to the truth than I originally thought!

When you think about it, your white sheet of paper is lit with roughly the same light intensity across. And if you don’t change the working distance, it behaves a little bit like “cropping”. You could also see that as the difference between different sensor sizes. You would have the same exposure on a FF sensor area and a m43 sensor area. The total light gathered wouldn’t be the same, but since the light intensity by area is the same, the exposure is the same. My analogy is probably horrible, but I think it’s a little bit the same logic in the end!

Have a nice day!

Cheers,

Julien