Sensor Size & Magnification

A crop-frame or APS-C camera does not let you get closer to your macro subjects.

It just doesn’t. Using a camera with a smaller sensor does not increase the magnification of your system. Magnification is a function of the lens that you are using, and where it is positioned, relative to your sensor. Sensor size has nothing to do with it.

For those who would rather watch a video than read my ramblings, here it is - enjoy!

Before I get back to the blog, if you want to know where to get your Mitutoyo objectives, there is a section towards the bottom of this post that will give you the link you are looking for… or, come to think of it, you could just use this one…

www.lightglassoptics.com

Now - where was I?

I am not exactly sure where this story first began, but I've been hearing it for many years. If you hang around macro photographers long enough, you will eventually hear somebody say, "I love me them there APS-C cameras and all that extra magnification”. If you ever actually get into a discussion with one of these folks, you'll realize what a persistent misunderstanding this is. I have had some very angry pushback from photographers who tell me I just need to look at the pictures to see! And that is the problem with any good optical illusion - you can’t see it - until you can.

Macro lens on a full frame DSLR

The same image, but on a crop-frame body (same lens)

Well, for crying out loud, it actually is bigger!

Actually, it isn’t. But it is a very convincing illusion. The reason that this illusion is so powerful, is because we have no way of knowing that the second image is smaller than the first. By convention, we deliver finished photographs in several standard sizes, like 8” x 10” or a 5” x 7”. But this tells us nothing about the original size of the image. If we make two 8”x10” prints, using both of these photographs, the ichneumon wasp will in fact look bigger in the image from the crop frame camera. But because today's cameras are so advanced, it is quite literally impossible for us to tell that the Pixels in the second image are spread out more than the first.

Another way of putting this is that, the wasp looks bigger than the second photograph, because we have enlarge the photograph. Not the wasp. And that is the difference.

Most macro lenses offer a maximum reproduction ratio of 1:1. That means that a 10 mm x 10 mm will be represented as a 10 x 10 mm square on either sensor. And to complete the illusion, all you need to do is enlarge the smaller photograph until it is the same size as the larger.

That is why this is an important concept for macro photographers. Depending on how aggressively we crop and then enlarge our photographs, the resolution will suffer to a greater or less or extent, as the pixels move apart during the enlargement process.

But none of this means that a photographer cannot have a legitimate preference for the smaller sensor size cameras. It is perfectly reasonable to prefer composing macro subjects on a smaller field of view. Knowing that these images will be blown up to make prints is of little concern, as the resolution of the sensor on even the least expensive camera today, is more than enough for a sharp image at normal print sizes.

For example, if your favorite macro lens is a Tamron 90 mm F2.8, a true one to one macro lens, and if your favorite subjects are ladybirds, a crop frame camera may be a better choice for composing your shots. That is because a 10-12mm subject will cover approximately half of the frame in your composition. That's close, but not too close. Now say you use the same lens on a full frame camera, the insect would suddenly look very small in the frame. Presuming that the insect has not grown since you took the first photograph, it will still be 12 mm on your sensor, it will just take up less than a third of the image instead of almost a half.

You can also think of this in terms of pixel density. I'm not suggesting that pixel density is the ultimate determinant of quality in a photograph, not by any means. But it is one way to look at the situation. The pixel density of the D850, a full frame camera, is approximately 53,000 pixels per square millimeter. That is actually the same pixel density as the sensor in the D7500. If pixel density was the only important factor in sharpness and resolution, then you can immediately see the detrimental effect of enlarging the crop-frame image by 30%, as enlarging the photograph by 30% will also reduce the pixel density by the same factor, 30%.

Enough already! There's a lot of other stuff in this video that does not involve mathematics. I talk about how to make a very specific kind of ping-pong ball diffuser, for using with long working distance microscope objectives. It's a very cool project, and not particularly difficult, but will yield awesome results, guaranteed.

This is a 3 mm fly photographed inside the ping-pong ball diffuser.

Below are three of the characters that I mentioned in the video, Audrey, Winston, and maggot.

Towards the end of the video I introduce you to a new vendor, who has an amazing deal for macro photographers. The name of the company is Lightglass Optics, and it is owned and operated by Mr. Jeff McDowell. This is a link to Lightglass Optics.

There is a very good reason that I'm sending you over to Jeff's shop. He is selling brand new Mitutoyo M-Plan infinity corrected, apochromatic, long working distance 5X microscope objectives for the best price I have ever seen. Admittedly, this is the cheapest M-Plan LWD Apo objective that Mitutoyo makes, at only $752. In case you're interested, the 10X version of the same objective is priced at $944, while the 100X objective is slightly more expensive, at $3,781.

It is my personal opinion, that the Mitutoyo M-Plan 5X objective is the best lens for extreme macro photography, available today. But I will be the first to admit that there are some other incredible optics out there, that cost in the thousands and even tens of thousands of dollars, that I will never see, let alone look through!

Lightglass Optics is selling this lens for an amazing $420. He has a limited number of these incredible objectives, new and in the original factory packaging. This represents a saving of $320 below the list price. Even if you are not currently doing any extreme macro photography, you should jump on this without hesitation. This is one of the objectives that holds its value on the used market. There are very few pieces of photography equipment that will give a lifetime of service and hold their value, like these.

You want a $200 fake, or the real McCoy (or McDowell, in this case)

The objective shown above is on loan to me from, awesome friend of the show, Glenn Martinez. He purchased this lens from a Chinese reseller, and I think we both have a reason to doubt it's authenticity. Don't be caught with one of these. Instead, go and buy a the real thing, from Jeff.

That’s how much grasshopper fits on a crop sensor at 5X

The video doesn't stop there! I started to tell the story of my discovery of the Eudiagogus pulcher sesbania clown weevils, from last weekend. It is pretty unusual for me to come across a new species of insect, that I have never encountered in all my years of doing this. Come to think of it, I have never even seen a photograph of one of these amazing creatures. Their exoskeleton is crusted with opalescent spheroids that makes them glitter in the sun, but that doesn’t make them any easier to find. Anyway, there's more to the story and I will share it in the future videos. In the meantime here's a close-up of one of these creatures, in all it's glory.

Eudiagogus pulcher, detail from thorax

There was one last announcement in the video, and I'm going to repeat the announcement here. In the not too distant future, I will be releasing a video course on extreme macro photography. I still don't have a title or a hosting site, but the content is coming along nicely. I plan to release a collection of videos every few months. Each selection of videos will ultimately form a chapter in my master class. The first chapter will deal with the intricate and frustrating business of preparing tiny insects for photography. Each video in the course with cover a specific subject. For example the first few episodes will cover equipment and supplies, posing and positioning, micro-manipulation techniques, preserving and storage, to name a few.

I'll have a lot more for you in the coming weeks, including where the course will be found, how much it will cost, and all the other pertinent details. I am very much looking forward to this experience, and hope you are too.