Does "Crop Factor" still apply when using a "crop lens" (a specialty lens designed specifically for crop sensor cameras) on a crop sensor camera?

Tom-Thomas said:

Oh boys, this is exhausting. Back in the days, the terms "crop factor" and "equivalent focal length" didn't exist. We just knew and understood that as the film size you use increase, you need longer lenses to get the same FoV as when you used a smaller film size. And, back then, a lens is a lens. Nobody made lenses specially designated for different film sizes (note that I said different film sizes, not different format cameras). I blame the marketing departments of camera manufacturers.

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Actually only the large format lenses were designed for several different film sizes but otherwise most lenses for medium format down to the Kodak disc were designed specifically for one film size.

Tom-Thomas said:

I did say, "... lenses specially designated for different film sizes (note that I said different film sizes, not different format cameras). Did the Olympus lens you mentioned had a designation saying it is specially for half film film? Tell me what this Olympus lens is, so I cam look it up.

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Olympus (and others) made TWO series of lenses specifically for the Pen F half-frame cameras. They are labeled "Zuiko F". Call them "cropped" if you like, they had smaller image circles for the smaller 35mm half-frame film format. Instead of a 50mm "normal" lens, their "normal" was 38mm.

http://www.subclub.org/shop/penf.htm

Tom-Thomas said:

I did say, "... lenses specially designated for different film sizes (note that I said different film sizes, not different format cameras). Did the Olympus lens you mentioned had a designation saying it is specially for half film film? Tell me what this Olympus lens is, so I cam look it up.

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See here for the older Olympus Pen half frame (18 lens) system: https://en.wikipedia.org/wiki/Olympus_Pen_F
Unfortunately, Olympus re-used the "Pen" designation for current digital offerings, so in your research be careful that you don't mix references to the lenses for those digital offerings with references to the older film cameras.

There are plenty of large format lenses designed for specific format sizes. For example, you will find a 105mm that is designed for 4x5" and a 105mm designed for 5x7". They both are exactly the same on a 4x5" camera, but only one will fill a 5x7" film with a wider picture angle. The 5x7 film doesn't have a wider picture angle -- the lens has a wider image circle, and the larger film can capture it.

This is exactly the same with a full frame 105mm lens on a full-frame camera, and a "cropped" 105mm lens on a APS camera. The "cropped" 105mm lens will produce the same image on both cameras, but only the full-frame lens will provide a wider picture angle on the full-frame camera.

Chan Tran said:

Actually only the large format lenses were designed for several different film sizes but otherwise most lenses for medium format down to the Kodak disc were designed specifically for one film size.

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The Pentax adapter that permitted lenses designed for the Pentax 67 to be used on the Pentax 6x4.5 cameras was not an afterthought - it was part of a comprehensive medium format system, intended to serve the needs of photographers who used more than one different size of film frame.
And of course the 35mm film backs made for Mamiya and for Pentax 6x4.5 cameras did the same - allowing lenses for both systems to be used effectively for both film sizes.

xkaes said:

There are plenty of large format lenses designed for specific format sizes. For example, you will find a 105mm that is designed for 4x5" and a 105mm designed for 5x7"

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Although in most cases such designations usually refer to the maximum frame size that they are usable for. Unless they have other peculiarities, like being matched to a particular rangefinder, those lenses are usually usable on smaller film sizes - just as Canon EF lenses are usable on cameras with a smaller digital sensor.

xkaes said:

There are plenty of large format lenses designed for specific format sizes. For example, you will find a 105mm that is designed for 4x5" and a 105mm designed for 5x7"

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Generally the size specification of a large format lens only means the largest film size you can use with the lens. Wouldn't often you use a lens with a larger frame size so you have room for shifting?

You can play with large format lenses more than lenses for smaller formats, but when a lens is designed they keep a maximum format in mind. You can use just about any lens on smaller formats, such as 6x7 lenses on 35mm, but they were not designed with that in mind. Most of the large format lens sales material that I have list the format it was designed for -- which, of course, is the maximum. They don't bother to list all the smaller formats.

Getting back to the point, lenses are designed for FORMATS, not films. Just as in large format cameras, you can use 4x5" film, or 120 film with 6x6cm to 6x12cm formats, and you can have submini cameras with 10x14mm images or 10x50mm images.

Just like with film cameras, with digital cameras you have lenses designed for all sorts of formats from 24x36mm down to 8x11mm sensors. With all of them, as the film or sensors gets smaller the focal length of the lenses get shorter to maintain the same picture angle -- and as a result, the image circle gets smaller, and the lens gets smaller too.

Tom-Thomas said:

But did Nikon (market) designate that 180mm f/2.8 ED AIS Nikkor as it is specifically for 35mm?

Of course that 180mm f/2.8 ED AIS 180mm f/5.6 Nikkor-W is used for a 4x5 camera because of the lens mount, which will not fit their 35mm camera. But are you saying that even without the lens mount issue, optically it cannot be used on other formats?

I did say, "... lenses specially designated for different film sizes (note that I said different film sizes, not different format cameras).

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I have a Sinar made board that enables me to mount a Nikon F mount camera on a Sinar view camera with a 4x5 back (thus also larger than 4x5 via reducing backs). Thus any view camera lens can easily be mounted in front of a Nikon 35mm camera (also Z via FTZ adapter). One could concoct such a board for other camera brands as well.

Tom-Thomas said:

I may have argued in a passionate and blunt manner here

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It does appear from my perspective that you've been getting very worked up about all this.

It seems that most of the factual information in relation to your question has been provided to you anyway, and as such, this should be sufficient in helping you understand how the crop factor works, and also where external sources may be unfortunate or inaccurate in how they informally describe its basic tenets.

As to the matter of insults - "it takes two to tango." From the get-go (starting post #6), you've expressed yourself in what I'd qualify as an exasperated fashion and have implicitly insulted virtually every participant in this thread of not being able or willing to read your post. That this boomerang after several pages ends up flying back into your own face - I'm afraid this is entirely your own doing, and as insults go, there's really not much being cast into your direction.

So coming back to your earlier request in #24, I think this would be a good time to lock this thread. In general, if you have questions about locking threads, or concerns about insults, we have a 'report' function that you should use. Don't create drama. State your case, we'll look into it and intervene as necessary.

Also, consider stepping back from the keyboard once in a while whenever you feel you're getting agitated. Locking this thread may be the best way forward as it removes the need to keep coming back to this and continue scratching the itch.