TS-E on the cheap? For architectural photography

Steve Balcombe wrote:

AmateurArchitectural wrote:

The T/S lenses benefit greatly from being used on full frame

Can I ask how? The IQ of a crop is presumably higher away from the vignetting and focus problems of the outer edges of the TS-E image circle. The difference between 18 and 20 Mp doesn't seem critical for my purposes.

The difference between 18MP and 20MP is very minor, agreed. But the higher image quality of full frame (used optimally) is significant.

He asked to explain what would give the higher IQ. In reality, the IQ differences are not that big, when you use equivalent settings.

Remember you are talking about investing a very large sum of money in a lens to do something which you can already do, albeit with some disadvantages, in Photoshop. Second best quality is presumably not what you are striving for!

The argument about lower quality towards the edge of the image circle doesn't really hold water. The 17 mm lens is not quite as sharp as the 24,

The 17mm f4 is more than sharp enough to give great results still with 1.4x TC. On APS-C you do not need that TC.  Anyway, if the center of the lens is sharper than the borders, you will get less difference between center and border on APS-C. Which just happens to be the case with the 17mm anyway.

and to use it as a 24 mm equivalent on crop means using 1.6x greater enlargement of any imperfections and aberrations. Double whammy.

Incorrect. The CA will lessen on APS-C (due to the nature of CA).

There are cases of full frame lenses which perform better on crop - one documented example is the Nikon 70-200/2.8 which was current a few years ago when Nikon had no full frame DSLRs. It was optimised for performance in the centre of the frame and had (relatively) poor corners.

It is nonsense that this lens was "optimized for performance in the center". It is a film era full frame design, when digital DSLRs were not yet replacing film SLRs (2002 introduction).

But this is unusual - most full frame lenses perform better on full frame sensors.

Not true. Most full frame lenses perform just fine on APS-C, with better border performance. Of course, the lenses which have great border performance on FF won't show any border improvement on APS-C. I could give many measurement results which illustrate this, but I guess that is rather pointless.

I've never used FF (I may indeed hire to find out!), but most seem to feel that Live View gets you nearer than even the best pentaprism. My first instinct was to chuck money at it and go 6D+24mmTS-E, but answers above have really opened my mind to some other options.

I would never argue against having an open mind. I am completely open-minded about that.

The current cheapness of the 60D does make it sound like a good contender - thanks.