Idea for mimicking STF effect without APD filter

[Langstrum]

I've just had an idea and I want to share with you. Since I'm interested in STF effect, I want to find a way to mimic it without using APD filter.

Basically, to achieve the same effect, I have to block the light gradually from center to the edge of the iris. It can be done easily with APD filter, but what if I don't have that filter? Well, the aperture blades can do the same thing if they're allowed to close or open DURING the course of exposure (in normal way, the iris is closed or wide opened before the exposure).

To demonstrate that, I used Helios 44 58mm f/2 with 13 aperture blades, so that the bokeh will be almost rounded at every apertures. I set the shutter speed to be quite slow, but not to slow to prevent shaking when I turned the aperture ring. I focused at f/2, and turned the aperture ring to around f/4 immediately after pressing the shooting button. I repeated that several times with the hope that some of the exposure can be synced with the movement of the blades. 

As the result, you can see that the two cases in between (f/2-4) show diffused bokeh balls, while the f/2 and f/4 images have more defined bokeh ball. 

The effect can be done much better if I can control the speed of the aperture blades. The best case is Sony or any other camera company can engineer the camera to control the aperture blades to let them open or close during the course of exposure. I want to suggest this idea with the hope that I can have STF mode on the camera in the future.

For now, if you want to do the same thing in a more practical way, you can try slow flash sync and close down the aperture ring in the long exposure time after the flash is off.

Do you think it's feasible to control in camera?

PS: someone just told me that Minolta came up with the same approach long time ago but no one is currently using it.


 

[Username]

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[Langstrum]

Is that any keyword for me to start searching more details of this tool? I have no idea.

I tested the effect at night, when I can shoot with longer shutter speed (5 sec) and the bokeh can be controlled more precisely.

Here is the photo shot at f/1.2 (SLR Magic 35mm f/1.2 CINE)



And here is the photo shot with "STF stimulating technique". At the start of the exposure I used f/11, and then rotated the aperture ring to f/1.2 slowly.

[Guest Jaf-Photo]

1 point for creativity.

-2 points for practicality.

[Langstrum]

1 point for creativity.

-2 points for practicality.

 

Yes I know it has limitation, but my point is demonstrating that the STF effect can be achieved. With the help of camera control, the apeture blades can be allowed to move while the sensor is being exposed and the technique can be applied under fast shooting speed condition. 

 

I want Sony to hear and put that to a camera, probably through firmware update. Minolta had Aperture bracketing to merge different exposures with 7 stops of aperture to achieve the same thing, but the application was removed. This method can be better since we need only one exposure, but it requires more advanced machine controls. 

[Guest Jaf-Photo]

To be boring/realistic it would require a lot of firmware development, i.e. costs. Sony isn't known for spending hugely on firmware updates. Furthermore, the STF style is a niche and the easiest way to achieve it is to use an STF lens. Sony would not want to undermine their sales of STF lenses, either.

 

So all in all, a good effort but personally I don't even like the real STF look.

[Steve C]

On 2/1/2018 at 3:02 AM, Username said:

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Are you totally unable to post without gratuitous hubris? In other words, put up or give it a, rest? Is this not an open debate to exchange thoughts? 

[Chrissie]

6 hours ago, Steve C said:

Are you totally unable to post without gratuitous hubris? In other words, put up or give it a, rest? Is this not an open debate to exchange thoughts? 

It's a little late for your outrage: "Username" got kicked out of this forum about half a year ago ...

[Steve C]

I'm shedding tearz an stuff to read dat.