Originally posted by ElJamoquio The question then is whether or not a, say, D7100 + 18-35 f/1.8 (not very wide or very long) is cheaper than D600 + Sigma 24-70 f/2.8, for example.
I will say again (if you permit me) that equivalence is actually very important when you're considering what size of sensor you want to purchase (which is part of what this sub-forum is about).
...they're exactly the same, the only difference is what the number is in the exif. That's completely irrelevant.
So then, it comes down to other factors, camera cost, lens cost, lens weight, size, distortion, bokeh, etc. Usually those things (except camera cost and camera weight) skew slightly in favor of FF. Sharpness, CA, colors skew heavily in favor of FF.
Equivalency is a very small part of lens performance. As usual, you try and make a point by focusing on a very narrow area of lens performance, while ignoring others. For exposure,ƒ 2.8 on FF is the same as ƒ2.8 on APS-c. And even based on equivalency, an APS-c camera can do anything an FF camera can do for 95% of images that can be taken with the camera.
These are the attributes or lens performance.
Focal length
Aperture as it relates to the regulation of light transmission
Resolution
Aperture as it relates to Depth of Field
While the in Aperture (equivalency) it is a formula explaining how DOF in one system relates to DoF in another. By nature it explains how the systems are the same, not how one is better. But equivalency also says that for 85% of the Aperture settings, there is an equivalent setting on the other system.
I've long suspected that the reason you don't post pictures on the forum, is it would be embarrassing to your argument to have people analyze your photos to see how often you actually use your camera wide open, because for equivalency to matter, you'd have to use your camera wide open at ƒ1.4 all the time. Otherwise you'd have no argument. I tend to use ƒ5.6, as it's the sharpest setting on the majority of lenses, on both APS-c and FF.
You have always said for what you shoot, FF is cheaper. But no one has a clue what you shoot, or even if you ever take any images. IN that sense you have only no credibility, and I'm probably the only one who even takes the time to point out the fallacy of this non-sense.
I could see posting a bunch of great pictures, that couldn't be done with an APs-c camera, which is problematic in itself, because the fact that you took a picture with an FF camera, usually in no way implies you couldn't have taken it with APS-c. But every now and then some one comes in with an FF image shot at ƒ1.4 or an image that for some other set of circumstances could only have been taken with an FF camera, so it's unlikely but not impossible. And if someone who was a fan of that style wanted to know how you took the image, it would be informative to tell them to buy FF. it would make their life easier. To anyone not a fan of that style, telling them FF is cheaper, is misleading. Because only for those who make a habit of shooting wide open, is equivalency even relevant. For most ƒ-stops, equivalency doesn't determine you can't do something, it tells you how you
can do something in an equivalent fashion. Many FF proponents have flipped it on it's head.
So except for a few people, and you haven't even shown us that you are one of them, they can buy a K-3 with a DA 18-135, and have a more practical, functional system than buying a D610 and 24-85 or whatever it is, and save $500. One system has more range, the other can produce narrower DoF, so roughly equivalent depending on what you treasure. The APS-c won't do as narrow DoF, but the D610 can't do telephoto. It would need a 200mm lens to be equivalent to the K-3 with Kit.
The systems are roughly equivalent with both not having important features the other doesn't, but the APS-c is cheaper.
FF is only cheaper, if you need a really good camera. IN which case, MF is cheaper, 4x5 scanning backs are cheaper, even though they may run you $100,000 K. After all according to FF proponents it's only the cheapest if it performs certain tasks best, and there are certain things only a Scanning back on a 4x5 will do best. SO does that mean the 4x5 $100,000 is the cheapest. It is for people who need that capacity. The fallacy of the argument is apparent to most, but not all. Saying a camera system is the cheapest for one set of circumstances, does not mean it's the cheapest camera. The qualifier must always be added.
What exactly is FF the cheapest for? An arbitrary level of DoF , CA control etc, accepted by a very few people as a standard. The fact that almost everyone who shoots APS-c has already rejected those standards, is lost on these poor proselytizers.