Focal length, regardless of format

rwreich said:

Hello, all!

I'm very curious to know if there are any inherent properties of particular focal lengths that might contribute to the aesthetic qualities of an image regardless of film format. For example, on 35mm film, the 85mm focal length is considered a pleasing portrait focal length because the format and the focal length combine to create an angle of view that also contributes a reasonable amount of compression. On 120 film, say 6x7, with an 80mm lens (a very similar focal length), the field of view is wider because the film is larger, which changes the angle of view.

So, to restate the question using the example, are there properties of the 80mm / 85mm focal lengths that are applicable across formats?

I'm not an engineer, but I can read math. I'm not a physicist, but I love learning about and applying physical properties. Any helpful replies would be appreciated!

-Wayne

Click to expand...

the answer is simply'No'.Ech format has its own normal and portrait focal lengths.

markbarendt said:

I'm not tracking your thought here, compression (mountains behind look close to person in foreground) or flattening (smaller nose v bigger nose in portrait)?

Click to expand...

Mark, I realised sometime ago that I choose my viewpoint/position for shooting sub-consciously and intuitively. It's how I walk to (or sometimes backwards away from) a subject often not in a straight lne, I may zig-zag to either side. I'm visually watching the juxtaposition of the elements of what's in front of me nad will know what FL lens to use. I'm not composing with the camera I just need to frame to .how I've pre-visualised.

Now I often play little visual games while out walking the dog, usually with no camera, and just watching perspectives, and how things visually change with distance, angle etc. I'm also lookong at different light & weather as we usually do the same walk twice a day

Ian

The following were clipped from an article on focal lengths from the Jan 2007 issue of Film & Digital Times.

This may have already been said, as I didn't read every post, but, the only change when using the same focal length on different formats is what has become known as the 'crop factor'.

I know portraits have been the main subject of this thread, but think of it in macro terms (it's a portrait of something small). If I use a 100mm macro lens at 1:1 on a 35mm camera, and take a photo of an object that is 3 inches by 4 inches, it will fill the frame. What is on the frame will be a 1:1 reproduction of that part of the subject that is 24mm x 36mm. If I then use a 100mm macro on a 6x7 at 1:1, I'll get a 1:1 image of a 6cm x 7cm area of the subject from the same distance. Move to 4x5, and now it doesn't fill the frame at 1:1, so I'll get an image of the full object at a 1:1 magnification, but I'll also get a half inch of background around the subject. But in every case, I was at the same distance, and I got the same magnification (which can be said to be the AoV), but I got different looking images, only because the different sized negatives allowed capture of additional areas because of it's size.

If you take a 150mm lens from a 4x5, and mount it to a 35mm, the only difference in the image will be how loose (on the 4x5) and how tight (on the 35mm) the crop is. If you did that, and took the 35mm negative, you can place it on the 4x5 negative, and everything will match perfectly, because the lens had no idea what format it's projecting on to, so it will always project the same image, with the same compression, the same dof, the same aov, onto the film.

This is how 80-90mm feels to me on different film formats. 85-90mm on 135 is boring and flattering. Good portraits, yea, for photo in international passport. IMO.
On 6x6 90mm feels like 50 on 135 and of 4x5 90mm is like 35 on 135 film format. Personally, I like 80-90 lens on 6x6 as portrait lens.

Independent of format:

the closer "you" are (the lens), the more perspective is exaggerated--where things in the foreground look bigger than things in the background

The farther you are, the less perspective is apparent--and things closer appear in proper scale to things farther away--things get "flat" perspective--orthographic or viewed from infinity look.

that's everything you need to know--it's all about how far you are to the subject and how far you are to the "background". For portraits, the "subject" may be the nose, but the "background" is the face and ears---

Mostly, a wide lens is going to give you unflattering portraits close up, and make for wide noses and other facial distortions. A tele will compress the nose, which is not necessarily a bad thing :} Other than that, anything longer than around 135 in 35mm is going to put you too far away to interact very well w/ your portrait subject, and possibly give you a little too much compression (although in the past I've used a Nikon AF 70 200 2.8 zoom for portraits and never noticed any real issues}.

I'm always reading that a 50 lens in 35mm is a "normal" lens, or close to how we see things, but that's only if you "normally" see things w/ one eye shut. With two eyes open, which is how we see, our normal is nothing like a camera lens. In fact, what we see is a composite image from both eyes that the brain puts together and sorts out to give us what we "see" as a unified view. What we see is not what is there. It's just how we have evolved to get an image of reality. Other animals have evolved to see it differently. Who knows what is really there? It's impossible to really know, as it's always being filtered through the viewer's own particular programming. We always see relative reality, not true reality.

momus said:

Mostly, a wide lens is going to give you unflattering portraits close up, and make for wide noses and other facial distortions. A tele will compress the nose, which is not necessarily a bad thing :} Other than that, anything longer than around 135 in 35mm is going to put you too far away to interact very well w/ your portrait subject.

Click to expand...

I actually believe this is a myth with a practical basis.

The real issue is the normal viewing distance to a print. Simply put if you use a wide lens you need to print larger to make it look normal.

Try this experiment. Grab a camera and stand between your coffee table and your sofa and point the camera at the wall and note where the corners fall. Switch to a shorter lens, now where do the corners fall.

Now imagine that the distance from the camera to the wall is actually the distance from the camera to the subject. It's this distance that defines "the relative look of size of the nose".

If you print larger than imaginary corners you found you get flattening, if you print smaller than the imaginary corner you found on the wall in the nose becomes visually more prominent.

If you get an overly prominent nose, you haven't printed large enough.

You may feel it's a myth. That's fine. Go look at a fisheye portrait sometime You could print one of those things billboard size and view it from 600 yards away and get exactly the same distortion as a 4x6 print. Just bigger. Even a 50 is going to distort in a head shot. Lenses distort, it just depends on which way you want to go w/ them.

Ian Grant said:

There's no logic in that statement At the same aperture the 150mm lens (on a 5x4) will have considerably less DOF compared to the 50mm (on 35mm), you've also chosen FL's for each format that have a relatively close FOV.

If you were to state: "A 50mm on a 35mm film camera may have the same (approx) FOV as a 100mm on a MF, and the same for a 150mm on a 4x5..... they will each have a differentDOF when all three formats are shot at the same aperture." Then that makes sense.

Ian

Click to expand...

My bad. I meant to say they have the same FOV, but different DOFs.

momus said:

You may feel it's a myth. That's fine. Go look at a fisheye portrait sometime You could print one of those things billboard size and view it from 600 yards away and get exactly the same distortion as a 4x6 print. Just bigger. Even a 50 is going to distort in a head shot. Lenses distort, it just depends on which way you want to go w/ them.

Click to expand...

Fish eye lenses are odd balls, so what? Rectilinear lenses are not. If you view any rectilinear print from the same distance the camera saw the subject it will look normal.

The practical basis that I mention is the wildcard momus. I'm right on the science but most people don't print 20" or 24" print widths from the short edge of 35mm film in the example I gave. They print 11x14 or 8x10 and if you point a 105 or 130 lens at the wall in my example you'll see that those focal lengths come pretty close to those print sizes. Hold an 8x10 at arms length and an 85 or 105 lens makes a normal looking print.

momus said:

...
I'm always reading that a 50 lens in 35mm is a "normal" lens, or close to how we see things ...

Click to expand...

A reasonably good description I found with a good example:

https://en.wikipedia.org/wiki/Normal_lens

What I consider a "normal" lens on an SLR is one where I can keep both eyes open and the size of objects in the viewfinder match what I see with my other eye.

See post #12...

http://www.largeformatphotography.info/forum/showthread.php?37633-widest-lens-that-covers-8x10/page2

rwreich said:

Hello, all!

I'm very curious to know if there are any inherent properties of particular focal lengths that might contribute to the aesthetic qualities of an image regardless of film format.
-Wayne

Click to expand...

The simple answer is "no".
However, in real practice, shorter focal length make it easier to create larger apertures. E.G. a 50mm standard lens for 35mm format can easily be built with a maximum opening of F/2 or even F/1.4. But a 150mm standard lens for 4x5 inch will typically be F/5.6. Shorter focal lengths therefore allow faster speeds. Also, shorter focal lengths allow lenses to be built smaller an lighter, making them easier to handle. Street or action photography is better/easier done with a 35mm camera with 50mm lens than with a 4x5 inch with a 150 mm lens.