tradergeorge Loc: Newport, Kentucky

That is one of those "all things being equal" situations. It is a well known fact that a 200mm lens designed for a FX sensor will give the angle of view of a 300mm lens when used on a DX body. This is a function of the interaction of the lens and the sensor, which always must be taken into account....That is why I said earlier than a 200mm lens is a 200mm lens, except when it is not...

oldtigger Loc: Roanoke Virginia-USA

a 200mm lens is a 200mm lens, always, no exceptions.

tradergeorge Loc: Newport, Kentucky

Of course it is. However, that statement is worthless when you get something less from that focal length than you otherwise would. As an extreme example, A 200mm lens focusing on a large format negative will give you a different angle of view than if it is playing to a 35mm...The principle is the same with a FX sensor vs a DX sensor....

You can parrot all day that they are the "same", but the image you get is definitely different depending on what it is projecting to...

moonhawk Loc: Land of Enchantment

Yes, but the OPs question was about putting different format lenses on the same camera--Therefore 200mm is 200mm is 200mm. IOW, the question was not about what the lens is projecting to, but what it is projecting from.

And, I always heard that large format lenses in general aren't as
sharp as good 35mm lenses, because covering such a large image area, they didn't need to be.

I have heard recently that the newer medium format lenses for digital backs, however, are very sharp.

tradergeorge Loc: Newport, Kentucky

The OP's question WAS about putting different lenses on the other camera....But the second question and implication was how they would perform compared to the camera they came from. That is why he asked about a "crop factor"....That only comes into play when you are comparing two different formats. This makes my answer relevant and your comment to me a pithy observation of an irrelevant truism.

f8lee Loc: New Mexico

Ugh - this is getting tedious.

This is wrong. Two lenses of the same focal length have the same focal length - that is the ONLY thing that can be concluded from this datum. Once again, the angle of view is based on the focal length AND the size of the sensor.

Ergo, a 150MM focal length lens on an 8x10 view camera would be a wide angle lens (assuming it's projected circle is large enough to cover the entire sheet of film without vignetting). That same 150MM focal length lens would be a super-duper telephoto on a cell phone image sensor.

Here's a simple way to grok this:
1) get a sheet of graph paper. Draw a horizontal line 1 inch tall near the left edge, and just below that another horizontal line 5 inches tall.
2) next, place a dot 6" to the direct right of the middle of each of the above lines. (6" is about 150MM, but your graph paper is likely in fractions of inches)
3) now, get a ruler and draw a line from the upper end of the 1" line through the dot you just placed. Then draw a second line from the bottom of the 1" line through the dot.
4) do the same thing with the 5" line - draw a line from the top of the 5" line through the dot and then from the bottom through the dot

Now, the dot represents the focal length - here about 150MM. Note how the ANGLE OF VIEW is vastly different between the two drawings? THAT's what you are all talking about. The angle of view is much wider on the 5" line than it is with the 1" line (for extra credit, guess what it would be if you drew a 1/4" horizontal line and did the same thing with another dot 6" to its right). What makes a telephoto lens a telephoto lens is it's angle of view - a narrower angle of view means the lens "pulls in" the scene which it can see - narrower angle of view = more telephoto effect. Easy peasy.

Again, "crop factor" is a marketing term invented to make it easier for the hordes of photographers who were used to shooting 35MM film in days of yore, in order to allow them to get a general sense of what a given focal length lens would "behave like" on a digital camera with a sensor smaller than 24x36MM (the size of a 35MM film image area, now known as "FX"). There is nothing inherently special about "FX" other than it representing what the 35Mm film size was, and again, if it instead were true that 6x6CM format (Hassy) was ubiquitous and the vast majority of photographers "knew" that an 80MM lens was "normal", then the Hasselblad format might have been considered "FX" and the 24x36MM "sub-FX". But because 35MM film (which, when it first appeared in the still photo scene, was called "miniature") probably was used by at least a hundred times more photographers (maybe a thousand times more) than 120/220 roll film or sheet film, it became the standard concept as far as the marketing whizzes were concerned when interchangeable lens DSLRs first hit the market, as a way of explaining the concept of how a 50MM lens (which 35MM shooters considered 'normal') would give a view equivalent to a 75MM lens when placed on a DX body.

If you look at the technical specifications of any of the bridge cameras, you will see they speak of the "equivalent focal length" when the camera has a non-removeable lens; sometimes they will even specify the true focal length.

oldtigger Loc: Roanoke Virginia-USA

when it comes to focal length/angle of view and such, i think MT Shooter summed it up pretty well:

"A 50mm lens is a 50mm lens no matter what body you mount it on. You are implying that the lens changes when in fact it is nothing more than the portion of the image that is cast by that lens that is being captured by a smaller sensor. The image cast is exactly the same no matter what downsized sensor is recording whatever portion of that image."

The smaller sensor does not alter the lenses angle of view, it just throws away part of the image the lens offered..

f8lee Loc: New Mexico

That "throwing away" is equivalent to saying it alters the angle of view. The angle of view is what defines the image area - whether the shot is of the entire stadium or one individual across the field is determined by the shooter's position and the angle of view of the lens/camera being used.

If there were such a thing as an infinite resolution sensor, then you could shoot everything with an ultra wide angle lens and selectively crop down to your desired image in post - the resulting image would be identical to having used a longer lens in the original shot. That cropping is "throwing away part of the image the lens offers".

Meganephron Loc: Fort Worth, TX

RWR continue to split hairs. The manufacturers of these cameras reported a 1.5 magnification factor when the DX format was intoduced. While this is not true magnification, when you get your picture printed an 18 mm DX image will look like a 27 mm FX image. Remember too an 80 mm lens is a "normal" lens on a Hasseblad. A "normal" lens on a Nikon, Canon etc is 50 mm so an 80 mm Zeiss is a telephoto lens regardless of what you want to argue about focal length

speters Loc: Grangeville/Idaho

In fact, it was pretty much the whole story and he told it very nicely and easy to understand for everybody! What you are saying, is just repeating part of what he already said!