The Photoshop “Tilt-Shift “ filter, a meager simulation of the TS Lens


How many times have I come across people claiming that a “Tilt Shift” lens is not needed since it can be done in Photoshop. I don’t know if this is a matter of consumerism, ignorance or plain stupidity.  At best the PS Tilt-Shift filter is an imitation that only works under certain circumstances.

Tilt_shift_lens_Nikon

Tilt Shift Lens

So, what is this all about?

Tilt Shift lenses are crucial for architectural work, the reason is very simple.

The capture of a structure must be accurate, proportional and correct, reflecting reality.  I am not talking about creative architectural photography, that is different ball game altogether.

vallenI am sure that we all have been standing one time or another in front of a tall building and tried to capture the complete building into the frame.   Although we fitted a wide-angle lens and stepped back as far as we could, and still we couldn’t get the top of the building in the frame.

What do most people do?

Yes, tilt the camera in a slight upward angel. Eureka! Now we got the complete building in the frame.  Good isn’t it?  Nope. In the final picture the building will appear to fall backwards.  This is caused by the fact that the object  (front of the building) is no longer parallel to the Lens- and Sensor plane. The result is perspective distortion.

No problem, Photoshop will come to the rescue with a perspective correction. Yes, that will work. But have you ever wondered what happens with the pixels that are not there and need to be created through software to execute the correction?  Indeed interpolation, complex algorithms and estimation…. It will never be as good as the real thing.  Given, PS does a fairly good job.

Why not fixing it during the capture?  After all we are photographers and not retouchers.  

Well we could get a sky lift and move upwards to the point were the building fits the frame, a clumsy way but it works perfect.  Or use a Tilt-Shift lens, applying the shift up or down option.  It has a similar effect as standing on the sky lift, and no need for drastic perspective corrections in PS.

The question is “ does this warrant a 2000 Euro Tilt-Shift lens?”   I would say “No” if that was the only feature of the lens.

Parallelism unavoidable with standard lenses

Shift effect of TS Lens

Tilt effect of TS Lens

Now imagine that you need to capture a building, the corner head first with left and right the wings.  The wing of interest is the right wing (see picture) , more specific the spiral stairs, the left wing is of no interest and can be blurred.

In other words we must adjust the Focus plane so that it is no longer parallel to the Lens and Sensor plane….(Scheimpflug principle) . This is not going to work with a normal lens, since the Focus-, Lens- and Sensor plane are “fixed parallel”. Sure the distance can change but  not the parallelism.

Parallelism of a standard lens

Parallelism of a standard lens

We need a lens that can vary the angle between the Lens- and the Sensor plane; the result will be a Focus plane completely different then with a normal lens.  By changing the angle of the Lens plane versus the Sensor plane the Focus plane can be moved to other then normal places.  Hence we are able to create “in camera” a picture with sharpness on the right, and blurred on the left, although the distance between both wings and the camera are as good as identical.

Tilt principle

Tilt principle

 PS a meager simulation

Photoshop has a filter called “Tilt-Shift” that simulates this capture method; you can apply the filter to any picture (taken with a normal lens) and make it look like a Tilt-Shift lens effect.  “Make it look like”, that is the key.  It works as long as you will apply blur, it cannot create sharpness!  That is where the Photoshop Tilt Shift filter is “Busted”. Besides the fact that the Photoshop filter can not perform the “shift” function.  That is only possible at the moment of capture with a TS lens.

wallIn practice one would have to make very sharp pictures with a large Depth of Field (DOF). Forcing the capture with a stopped down aperture (high F number). But what if there was not enough light and you need to shoot with a wide open lens (F5.6, F2.8 or less) ?  That is not going to work, the DOF will be limited in the standard parallel plane, and off course not were needed. The PS Tilt Shift filter is not going to help out, as it can only blur. The picture on the left required a sharpness (focusplane) along the fence while shooting with a wide open aperture. The picture is taken with a normal lens, and can not be corrected with the PS TS filter.

Reflections, angle in = angle out

Another very nice feature of the Tilt Shift lens is it ability to avoid unwanted reflections, due to angle of occurrence. If light falls under a 45 degree onto a flat surface it will be reflected at an opposite 45 degreed angle.  Imagine you want to take the picture of bride in a mirror with a normal lens.  Pffff, very difficult framing since the photographer will be partial or fully in the mirror reflection.  A Tilt Shift lens with a horizontal shift, fixes that issue in a heartbeat.

It is not all rosy, the TS lenses are all manual focus and the light metering is not working. It takes some time to get the swing of it, once under control it allows for great shots.

No matter how we twist or turn it, the PS Tilt Shift filter cannot replace the Tilt-Shift lens. It does not even come near.  Try it if in doubt.

Of course if one only takes every so often an architectural picture, Photoshop will be your best ally and the investment in a Tilt Shift lens is out of scope.

Thanks for reading,

Steve

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