Putting the Sense back into Sensors - parts I & II
/So you weren’t buying it?
I went to all that trouble trying to convince you that the sensor of an APS-C camera does not give you any added magnification - but you still don’t buy it?
Well…. shucks.
Well, it really doesn’t. It is an illusion caused by the way a camera presents a preview of your image in the screen. But I explained all that last time, didn’t I? So what gives. It is just a very convincing optical illusion, and when you are convinced you are seeing one thing it can be hard to change your mind. Especially if you don’t want to.
I was going to just let it slide, but I’m glad I didn’t. For one thing, if an entire camera club in Hawaii disagreed with my explanation, I must not be doing a very convincing job. And secondly, it’s important. If you do’t understand the difference between the image on your sensor and what your camera’s screen is showing you, how can you make sense of really complicated stuff, like resolution?
I can’t stop photographing weevils
Anyway, I decided I couldn’t leave this sleeping dog just lying there, now could I? In the first video on this topic, I ended up cutting the demonstration and a section on sensor science, mainly in the interest of time, but also because I thought that it might be insulting to spell it out in a demo after explaining the illusion. My bad.
So I made another video, the demonstration, but I reshot it to make it all extra-extra clear. And then I felt guilty about wasting your time and decided to add a fun part to the video. But then the video was too long again, so I chopped in half and that, friends, is why there are two videos in this one short article! Here they are… the front half:
… and the back half:
As promised in the videos I am going to show you the graphics that were used in the video to explain the illusion - but first, let’s take a good look at the illusion. Below are the images, as they would appear on the sensor of full frame and a crop frame camera, respectively. it should be pretty clear that the only difference between the two is the size of the frame, right? Remember that both of these shots were taken with the same lens, same subject, same focus distance etc. The only difference was the camera body used.
See it yet? Imagine of the screens on the backs of the camera were proportional to the size of the sensor inside. The screens would like like this and there would never have been any of this magnification talk in the first place. BUT THEY AREN’T!
The screens on the two cameras are the same size. So the crop frame camera image must be enlarged significantly more to fill the screen on the camera. So that means the subject must also be enlarged proportionally. And that’s the whole problem. We assume that we are looking at comparable data on the backs of the two cameras, but we are not. The FF image is enlarged about twice, but the crop frame image has to be enlarged almost three times.
Let’s look at the subject again… only this time we can compare them as they actually appear in the image on the sensor…
Now let’s superimpose them…
Now do you see? The subject is not “magnified” by the smaller sensor, it is enlarged, disproportionately to the image from the full frame camera. So we are tricked into thinking that our sensor has somehow done the impossible, because our APS-C camera has enlarged the image while you weren’t looking. Look at it this way…
When we make something bigger before it gets to the sensor, using a lens, we capture it as a larger subject - and that’s magnification. When we take a small thing and stretch it out to fit on a bigger screen, we do so at the cost of degraded resolution, and that is called enlargement.
And just because our eyes aren’t good enough to appreciate the difference in the resolution, that does not make it any less true.
So, one more time, all together now…. A smaller sensor does not let you get any closer to your subject and it does not magnify the subject on your sensor. The only real difference is that the crop sensor camera shows you less of the image cone. And it is your - oh so sneeky - camera that seals the deal by blowing the resulting image up to fill your screen.
Now can we have some fun?
I’m not going to spoil the video… but I am going to give you a few links, affiliate links in some cases (which means that if you buy something using one of these links, I supposedly get a few coins from Amazon, because I am an affiliate, and that’s the way that works).
Here are the things I talk about in the back half…
Mitutoyo microscope objectives - My M-Plan 5X Apo LWD work of art arrived from LIGHTGLASS OPTICS last week and it is oh so very fine. I am going to do one or more videos all about this amazing optic, and when I’m done, you will want one. I talked to Jeff, the overlord of Lightglass Optics, and he said the objectives were flying off the shelves. I cautioned him about securing them more carefully, as they are fragile. He probably rolled his eyes, as one does when one encounters an idiot, but clarified that the lenses were selling fast. If you want one, call Jeff today, or regret not doing so for the rest of your life. His number, you ask?
505 235-9468
Call him. Do it now.
Next up… BONDIC!
I wouldn’t bother using it on leaves, like I did, but definitely try using it to build your very own retroflexicating semi-rigididified, trimagnetificated, opticodiffusionator assembly. Also known as a stick on a bendy arm with tracing paper.
Here is your link to Bondic that makes it all possible… https://amzn.to/3gxCqZS
And some sticks… these things are so useful in projects… https://amzn.to/2U5a3cK
And don’t forget the best diffusion tracing paper know to mankind… https://amzn.to/3qcaIFu
If you don’t already have an insect pin grabber, this one is pretty basic … https://amzn.to/3qcbnXu but use extreme care, as once you wrap this up in electrical tape you may no longer be able to recognize it and could confuse it with your car
Talking of electrical tape … https://amzn.to/3cPlqMz even if you don’t buy any, click on this link and look at the description - it has a 5.1% satisfaction rating! Must be a typo. I love the stuff.
Finally, if you want a drone just like mine, you can’t have one as mine is very unique and special. I did find the standard model that Phil Evans recommended - I hear it is very good…
I think that covers everything!
Until next week…
Next time - Mitutoyo Magic!