03-03-2020 01:39 PM
Correct regarding my DOF (and low-light) comment. It was indeed tied to the larger maximum aperature values of the primes.
BTW, that's a serious collection you have there
03-04-2020 11:15 AM
"...referring to those cases where the primes do have a wider maximum aperture than readily available zoom lens,..."
I can't argue that point but zooms are gettign even better. And, they are getting faster. The Sigma 18-35mm f/1.8 DC HSM Art Lens and Sigma 24-35mm F2 DG HSM Art Lens. From Canon the RF 28–70mm F2 L USM. A few years ago anything under f4 in a high quality, high IQ zoom was thought not possible. The good news zooms will get even better and faster.
Zooms are not easy to make. They have lots of issues to overcome way more than a simple prime. Sometimes it comes down to how much customer are willing to pay. But manufacturing is better and more efficient so more difficult designs can be created.
03-04-2020 12:33 PM
I think it is time to forget about "35 mm equivalents" that ship sailed 20 years ago when digital eclipsed film. Now you could argue that we should talk about "22 mm equivalents" since smaller frames have a much larger share of the market!
I strongly agree in principle. If you're going to use a particular camera, you should think in terms of how a given lens behaves on that camera, not on a camera of some other type.
There is, however, one case I can think of where it is useful to think in terms of "equivalents". If you're you're going to do a shoot with two cameras, one a full-frame and the other an APS-C, being cognizant of equivalents helps you allocate your lenses so as to avoid inadvertent coverage gaps. I realized that when for a couple of years I had only one full-frame camera but was doing a lot of two-camera events.
03-04-2020 12:39 PM
I don't know if I am disagreeing with myself or not, but the other place it is needed is when discussing zooms for small sensors. I have no idea how 4.5 - 18 mm relates to the real world, until you tell me that these are 25 - 100 mm 35mm equivalents. (Real numbers from my Olympus TG-5)
03-04-2020 01:10 PM
It can be a pretty useful comparison metric both to have a relative feel for how a lens will behave on a different sensor "format" and also to adjust with reference to shutter speed for handheld photos.
My first quality digital was a 1D Mark II with its 1.3X "sports crop" and I mentally adjusted focal length to get a feel for it moving from 35MM film.
03-04-2020 01:12 PM
Good points regarding use cases for equivalents. On my Vixia cam, the 3.67mm to 73.4mm marking on the lens is not directly useful
I sometimes take either stills or videos, then use my 3D software to infuse rendered assets. To get perpective correct, I set the 3D software's cameras to match exactly the physical camera/cam and lens settings. The software camera settings defaults to the 35mm standard (though you can change that). So it's just easier to enter in the 35mm equivalent values into the focal length field.
Side note/rant: On my Canon cam, unfortunately the sensor is marked as "1/2.3 inch" but that's ultimately meaningless since many manufacturers advertise that size yet can range from 7 to 8 mm. "1.0 inch" sensors are defintely not 25.4mm. They are much closer to 16mm. Sure hope the industry one day just marks stuff with the actual mm diagonal and not other designations that can vary. I think this also happens with medium format. Stating "MF" isn't enough since there are too many variations of the physical sensor size.
03-04-2020 01:37 PM
You see I really never did get into the whole crop factor thing until I got on some forums. It seems it abounds!
I guess it is because, for work, we used all different camera formats form 8mm to 35mm to 8x10 sheet film. There was no crop factor, or tele factor (?) then. That came about when the Rebels came out.
You just knew which lens to use one which camera.
03-04-2020 02:31 PM - edited 03-04-2020 02:35 PM
I have said before, so forgive me if you read this agian, that we are not really served well by using focal lenght alone as a metric for identifying what a lens will deliver. A lens does not produce recorded image without a sensor: thus, the focal length of the lens - which is a valid optical metric for the LENS is further imacted by what the sensor captures. Combining these two is how we come to equivalence, an attempt to reconcile this issue, given that common nomencalture refers to this in terms of what the lens and a FF(35mm) sensor will produce.
For me Field of View goes some way to reconcile this. So aruably, in the documentation printed on the lens box and other literature, it could be easy to have both the Focal Lenght (which is certainly a valid identifying characteristic) and the Field of view. For EF-S lenses this will be just one value for a fixed FL lens, a range for a zoom. An EF lens would have to display a table showing what FoV the lens+sensor combination will offer for both AP-C and FF bodies, perhaps with a simple diagram to clairfy the intent.
I am the first to say that this is not critical for the majority of people who buy a lens after looking through a one on a camera in a shop or seeing one in action elsewhere. However it is more of an issue as in the OP, where one is seeking a specific FoV for a crop sensor body.
I certainly experienced that with a couple of people from a local photography group. A fairly new person seeking a lens was impressed by a particular L lens that took a bunch of images on show - the images showed the full gamut of the lens' FoV on a FF camera. Not being aware of the impact of a crop sensor they purchased the same lens for their APS-C body and when it was delivered they were convinced the lens was faulty as it did not deliver the same results. This elilcited a dispute between the vendor, Canon and the purchaser until someone enlightened the purchaser.
I stil refer back to the article from DPReview that tries to explain this issue