Perspective correction preview (tilt/shift emulation)

[ariznaf]

I could not enjoy ML yet, as I have a 40D and there is not yet an official port.
But it will come and in the future I hope to buy a 7D and first thing I'll do is install ML in it.

One thing that I think would be easy to implement and will be great is a preview of perspective correction in LiveView.

It would be of great help in architectural photos, helping you compose the image and preview the area of the image you will be cutting later when you make perspective correction by software.

You could use the joistick to increase the perpective correction in one or another axis until you see the line convergence corrected. Thus you can see what part of the image will be lost and move the camera or use a smaller focal if it is needed.

Zooming in the image will help to make the composition.

Guiding line from the small axis would help to see what will be the final cut if you are not using the cloning brush to expand the usefull area.

Thanks  for your attention.

[a1ex]

It's possible, in the same way as defishing or anamorphic preview (with display filters), but not on 7D. You need a camera with CONFIG_DISPLAY_FILTERS enabled in internals.h.

I'm going to let somebody else implement it though.

[ariznaf]

Thank you for your quick response.

I understand for your answer that 7D and other cameras are not able to do it in real time as you cannot stablish a filter to make the perspective correction in the image processing on the fly (as it travels the pile line to the liveview).

It would be of help even if it is not done on the fly in cameras that are not able to do it on the fly.
I mean, using a buttom to trigger a "ghost capture" and see the resulting imagen static in the lifeview to see the corrected picture and the cropping rectangle.

Does 50D or 60D support the filters?

[a1ex]

60D and most newer cameras (also 550D) support display filters. The 50D/7D can do this only in playback mode (not Liveview), because we don't know how to change the display buffer address.

[Marsu42]

I'm going to let somebody else implement it though.

If someone can do it, it would be very useful - if doing perspective correction I often find that there are too few pixels on one side to leave the crop I want (hardware tilt/shift lenses fix this by always providing 100% sensor resolution). If there would be any kind of preview I'd know how much I have to zoom out...

[ariznaf]

Ok,  thank you,  I understand.
Any way  I think it is a useful and may be easy to implement feature in cameras that support filters.

That would be a thing in favor of 60d against 7d.

[Marsu42]

Any way  I think it is a useful and may be easy to implement feature in cameras that support filters.

I wouldn't know about easy to implement, but given the hype (though understandable for professional architecture shooting) around the €2000+ tilt/shift-lenses a helper for software perspective correction would be a feather in ml's hat :-)