New player

[Gaz]

I bought an A7iv and what I call a really diverse travel lens Sony 24-240, which has reached its limitations since I got home and I am back to regular habits.

I like playing with fast and long mm, but traditionally, I'm into architecture and street/urban photography, both of which have been revived by my recent tour.

Discuss:
One lens to rule them all.
60-600mm F4.5-6.3 DG DN OS super zoom for E-mount

One Camera to find them ( own A7iv already):


One lens to bring them all, and in the darkness bind them:

FE 24-70mm F2.8 GM II​

​

 

[Gaz]

oops

 

[AlphaWorld]

Much though you might want to mount a single lens on your camera and never change it no matter what you are photographing, it's not a practical idea. Not even quoting Tolkien will make it so.

Actually, that's not completely true. You can do it, but you must compromise. You must lower your expectations.

Lens design is always an exercise in compromises - the designers choose which aspects of the lens to compromise, and by how much. Lens purchasers then choose which bundle of compromises they are willing to accept.

Among the variables that affect a lens design:

• cost - one of the lens designer's key limits, Designing for a lower price means using fewer elements, less exotic glass, re-using existing components, using less rigid materials...
• size and weight - if we want a small and light lens, then we are enforcing limits on the other compromises - Sigma's early Global Vision lenses put less of a constraint on size and weight so they could improve image quality (and use less exotic glasses to keep costs down) - their 85mm Art was a sharp fast lens, but weighed a lot
• maximum aperture - a lens with a more limited maximum aperture (f/2 instead of f/1.4, for example) can be smaller and lighter and better in other aspects (fewer aberrations, sharper...) - Leica's Summicron range of lenses choose f/2 as their maximum aperture for those reasons
• focal length, especially range of focal lengths - the more focal lengths the lens must handle, the more complicated its design becomes (and the more aberration correcting elements are required). A prime lens can be much simpler than a zoom with a short range, which is simpler than a zoom with a longer range...
• focus distance - if we designed a lens which always focused at a specific distance, we could optimise it for that distance (such lenses exist, particularly in industrial applications, but also in phones). The wider the range over which we want to vary the focus distance, the more complicated it becomes - most camera lenses do focus to infinity (and beyond), but all have a minimum focus distance - making the minimum focus distance and shorter leads us into macro territory, and forces other compromises (ever noticed that macro lenses have limited maximum aperture?); there are extreme macro lenses (like Canon's 1-5x macro) which cannot focus to infinity
• sharpness - both at a point and across the full field of view. Do you want the lens to appear sharp at 24megapixels, or 60megapixels, or more? If you are designing for HD video you don't need to design a lens that appears sharp at 60megapixels.

And that's before we start considering aberrations, like spherical aberration, chromatic aberrations, flare, and so on. Each of these is its own balancing act. You want to address spherical aberration, so you introduce an aspheric element, but that can mean onion-ring bokeh due to the difficulties in polishing an aspherical elements...

These all interact, too. Introduce an extra element to address one issue, and you throw off another parameter.

If you want an extreme range of focal lengths, you will have to accept more compromises on other factors. Some are obvious, but the tricky ones are not: for example, you are going to have to accept less sharpness at some, or most, or all focal lengths. You will see more aberrations.

A key reason interchangeable lens cameras were invented was because no one lens can do it all. Plus we want to be able to change which bundle of compromises we are using depending on what we are photographing. If I am photographing a single flower, I'll be prioritising shorter focus distance and sharpness; if I'm photographing a bird in flight, I will want speed of focus, longer focal length, and sharpness (I like sharpness!).

I think the 24-240mm Sony lens was introduced with the first Sony E-mount video camera, and that's what it was designed for - for a 1080p camera (roughly 2 megapixels) - you can use it for stills, but don't expect it to produce really sharp images. That's an idea - I suspect that a 60-600mm lens would work very well shooting 1080p video!