47greyfox Loc: on the edge of the Colorado front range

Haha! Yup, that “reply” could be pasted into a LOT of UHH threads. 🥴😵‍💫😏

DE Stein

I'm piggy-backing on this post! I too have been so confused on this topic, to the point of embarrassment! I've been shooting on a Canon 80D. Early on I read so much about the wonders of a 24-70 F/2.8 that I decided I needed to have one. But, I was also told that on my 80D it would be the equivalent of an 38-112. To me, that suggested that I would be loosing the benefit of the field of view of the 24-70. So, I purchased an EF- S 17-50mm. When factoring the crop, this should give me something closer to the 24-70 field of view. Right?

I also wanted an 85mm for portraits. But my 50mm gives me about an 85mm field of view. So, is my 50mm essentially equal to an 85? Have I complicated this for myself? Or, is this kind of thinking necessary if one wants to get the specific field of view of a particular focal length?

I'm now shooting on an R6, so I feel my lenses are giving me what they say they're giving me!

Jack 13088 Loc: Central NY

There is nothing wrong with your understanding except for perhaps the penultimate sentence where you use the term "angle of view". I think of the angle of view as the angle of the scene that falls on the active part of the sensor. That is a property of the camera and the lens. So a 35mm lens is a 35mm lens no matter the size of sensor your camera uses. "Equivalent focal length" is ambiguous but usually means a 42mm x 36mm active sensor area. It is not a particularly useful number taken alone.

To further confuse the issue the meaning of the term "perspective" is determined by the CAMERA position and has nothing at all to do with the focal length of the lens.

I suspect expect for technical photography, on one says I want a certain perspective therefore i need a 34.268mm lens. If when looking in the viewfinder you need a wider view you either select a shorter focal length lens or back up. Keep mindful of what is behind you!

sippyjug104 Loc: Missouri

In layman's terms, the focal length of a lens is the distance measured in millimeters from the convex lens to a point where the image of a subject is projected in sharp focus on a target. In terms of the camera, the target is the sensor or film.

Thus, the focal length is a function of the lens, not the camera. The size of the camera sensor equates to its field of view.

User ID

I’m pretty sure the OP is wisely ignoring 95% of the replies in this thread. Most are useless, many are harmful.

Reeeeeeally classic UHH. Disgusting. There were about two brief replies that simply said “Yes, you’ve got that all right. Keep on keeping on”. All the rest are absolutely knee deep BS.

kenArchi Loc: Seal Beach, CA

I would like that lenses go by magnification.
A normal view 1x lens would show the same SIZE view as you see. A 2x lens will DOUBLE the view. A .50x lens would halve the view. Etc.
What is a35mm view?
If a 70mm lens view is the same view size as what I see, what lens mm lens would double the view, 100mm, 140mm, 200mm? Confusing!
So if I want a lens that is 3x view, what mm would that be.
I can care less about ANGLE OF VIEW, ANGLE OF VIEW.
Give me a true size view lens.
Isn't that simple. Better than trying to calculate what x view that 480mm is.

ecurb Loc: Metro Chicago Area

That option is one of the nice features of my D600. I shoot a DX 35mm f1.8 in full frame mode, the lens covers the full FX frame with burned in corners, like I used to do in the darkroom. My street photo setup.

SuperflyTNT Loc: Manassas VA

The angle of coverage really only comes into play when using a lens designed for a smaller sensor, (like a DX lens), on a larger sensor, (like an FX camera).

User ID

So just rename your lenses 1/2X, 3X etc and leave it at that. It’s child’s play and makes for happy children. Do it !

When you report back on your happiness and success, it’s hopeless to attempt to explain it in any depth. It only works for users (like you) who intuitively see the true simplicity of it.

williejoha

I cannot believe this question keeps coming up.
WJH

MrPhotog

First, congrats on the R6.May you enjoy it for many years.

The issue of comparing lens focal length to image size has been around since camera obscuras were made in the 16 th century—long before photosensitive film or electronics.

The movie makers had a similar situation 50 years ago. You could get regular 8 mm, super 8 mm, 16 mm, and 35 mm movie films. Each had a different frame size. Built-in zoom lenses were popular with the 8 mm cameras, but some had interchangeable lenses. These were frequently on a turret.

Adapters were available to allow using lenses from 16 mm cameras on 8 mm and super 8 mm cameras. There were (and still are!) adapters for using 35 mm movie camera lenses and also 35 mm still camera lenses on 16 mm cameras. Couple that to the first adapter and those lenses also worked on both 8 mm formats, too. Dr. Frankenstein would feel right at home with those tools !

The technique almost always works if you use a lens designed for a larger format on a smaller format, but it rarely works in the opposite direction.

This led to some interesting lens history in the development of 35 mm photography. A goodly amount of that history leads (like branches on a family tree) back to Oskar Barnack, and a few unknown people before him. Barnack and friends saw that the thin emulsion 35 mm movie film used around 1918 captured a much sharper image than the prevailing sheet film. It was so good that a film image just 18 x 24 mm could be enlarged to fill a 10-meter-wide screen in the movie theater.

So Barnack made a camera that used movie film— because it was the best film available.
To get double the advantage, he turned the film on its side in his camera and was able to get a 24 mm area between the sprockets. While movie film had exactly 4 sprocket holes for each frame, Barnack used 8 sprocket holes for each frame. That gave a frame 36 mm long and a small gap between frames.

The world would be a different place if he had done the ‘appropriate’ thing and chosen a spacing of 7 sprockets! The slightly shorter image would be much closer to the shape of 4x5”, or 9x12 cm films of the day. And a much better fit for 8x10 prints.

Once he had selected the format he couldn’t go to the store and buy a proper lens. He had to make a lens for it, because ithe format was bigger than standard movie film, and it was much smaller than roll film cameras.

Probably he should have designed a
43 mm lens, matching the diagonal, but instead he made a 50 mm lens. I suspect it was an easy compromise to maintain sharpness in the corners of that elongated frame. After that 50 mm became a standard, and every other company needed to match that to compete.

At the same time Barnack was tinkering with 35 mm movie film, Rolleiflex was building 6 cm film cameras, amateurs were using 6 cm and 7 cm roll films (120, 620, 116, 626, 122 sizes), and pros were using 4x5 press cameras in the field and view cameras in the studios.

The amateur bought a folding roll film camera with a 100 mm or 105 mm lens, or the press camera with a 135 mm lens. Amateurs aspiring to do professional work bought 4x5 press cameras, or their smaller (or metric) siblings. Then, as now, the quality of lens was important, and a lot of development went into designing 135 mm focal length lenses for 4x5 cameras.

So, in the 50s and 60s, as 35 mm use grew, and 4x5 waned, there was a lot of good glass already ground to 135 mm focal length, and factories set up to make more. It was relatively easy to put that glass in a helicoid focussing tube, and sell it as a ‘telephoto’ lens for a 35 mm camera. And around the 1960s, 135 mm became the most popular ‘second’ lens for a 35 mm camera owner. You could get decent ones at relatively low prices. The 100 and 105 lens designs from roll film cameras were also remounted for 35 mm cameras, and saw new life.

Remember, in the days before computers designed lenses (roughly 1978) all lens designs were drawn by hand and confirmed by grinding the lens and testing it, then repeating the process. It could take years to create a significantly improved design.

The nice thing is that most of the time a lens gives a sharper image in the center than at the edges. Using these lenses with smaller formats used the best part of the image quality they produced. This concept still survives when using lenses designed for full frame on cameras with cropped sensors. And you can still get adapters so you can mount the old 135 mm press camera lens designs on mirrorless camera bodies!

But films improved, too. 120 and 4x5 films got thinner emulsions and produced sharper images in 1970s than in 1920s. It was possible to shoot an image on a larger format and use the entire frame, or crop it to use just a portion.

With 4x5 film and a 135 mm lens one can snap a shot that has a moderate wide view ( similar to about 38 mm on a 35 mm camera—close to a 35 mm lens), crop that to match the image seen by a ‘normal’ 50 mm lens on 35 mm. Then crop it more to get the effect of a 100 mm portrait lens on 35 mm. And finally crop it to the identical size of a 35 mm frame, where it is the same as using that lens on a 35 mm camera.

Where you have a high-resolution image medium you can play around a lot more.

My Sony mirrorless lets me select shooting full frame, or APS-C. It essentially is doing the cropping and just using a center portion of the sensor. But why should I flip that switch? I can do the same cropping in post processing. Or maybe I’ll use a slightly larger area, with a marginal improvement in quality.

With cell phone cameras packing more pixels in smaller spaces, the trend is simply continuing. The new formats are smaller, but have great sharpness, and old lenses are repurposed for use with them. And as that happens we see that those old lenses were really very good in the center—and that is the only thing that matters.

BebuLamar

I don't want them to do anything except drop the crop factor and 35mm equivalent focal length. They only need to specify the focal length and the largest format it can cover.

DE Stein

So this is helpful, sort of! Assuming the picture was taken with a 50mm lens (and I understand that 50mm is 50mm is 50mm!), the sensor size will determine what I see in the actual photograph. My APS-C sensor will produce the smaller image, and the FF sensor will produce the larger image.

So if I want to replicate the larger image on my APS-C camera, I'll need to use something like a 35mm lens (1.6 crop factor) to get close to the FF photo... Yes?

R.G. Loc: Scotland

That's right, or putting it another way, smaller image = narrower field of view, larger image = wider field of view....

...therefore > smaller sensor = narrower angle of view, larger sensor = wider angle of view (for any given focal length)....

...which is why angle of view changes with sensor size (for any given focal length).

DE Stein

Ok, I get that. However, I find this makes lens selection for an APS-C camera more difficult! I have to take into consideration the impact the smaller sensor will have on the mm of the lens I'm wanting to use. The extra reach is nice on the long end, but the loss of width on the short end can be challenging!