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Zak Forsman

Rectilux Core DNA - non-rotating single-focus attachment for anamorphic lenses

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2 hours ago, Bioskop.Inc said:

So is this the reason that people think that the 54 is less sharp than the 36, especially when shooting with a lens wide open, because in fact you won't be shooting at the aperture that you think you're shooting at? So in fact, when shooting with a 54 you really are shooting at the right aperture & so it will reveal the taking lens to either be sharp wide open or soft - nothing to do with the attachement, but more to do with the taking lens?

Its definitely a factor, and it certainly helps to be aware of what is actually the limiting aperture in the system.  Even the Iscorama-54 isn't large enough to avoid stopping down an 85mm f/1.2.

Although I don't have the Iscorama-54 design prescription and can't accurately evaluate its performpance, I do expect that it has plenty of aberrations on its own, especially at full aperture.  A good test of the 36 vs 54 would be to use a prime lens with great performance that has an entrance pupil larger than 54mm.  The 85mm Zeiss Otus comes to mind . . .

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7 hours ago, Brian Caldwell said:

Its definitely a factor, and it certainly helps to be aware of what is actually the limiting aperture in the system.  Even the Iscorama-54 isn't large enough to avoid stopping down an 85mm f/1.2.

Although I don't have the Iscorama-54 design prescription and can't accurately evaluate its performpance, I do expect that it has plenty of aberrations on its own, especially at full aperture.  A good test of the 36 vs 54 would be to use a prime lens with great performance that has an entrance pupil larger than 54mm.  The 85mm Zeiss Otus comes to mind . . .

Well I don't have a 36 anymore (not for a long time), but do have 2 other Isco-Gottingen made anamorphics (widescreen 2000 & Iscomorphot s8/x2 - both fixed focus), so might be worth a try to see what the difference is between different anamorphic back element sizes.

The largest fast 85mm I have is the Helios 40-2, which is f1.5 & it looks like the pupil size is slightly larger than 54mm.

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This thread may be helpful for me. I just got the Rangefinder to use with my Takumar 50mm and Singer 16D. I did some testing with/without the rangefinder and the background is stretched vertically by quite a bit with the RF. Is that normal? It's rather odd looking compared to the "anamorphic only" footage. I can still return it and get the Rectilux but I wanted to find out if that's a characteristic of both, or just the RF.

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1 hour ago, AaronChicago said:

This thread may be helpful for me. I just got the Rangefinder to use with my Takumar 50mm and Singer 16D. I did some testing with/without the rangefinder and the background is stretched vertically by quite a bit with the RF. Is that normal? It's rather odd looking compared to the "anamorphic only" footage. I can still return it and get the Rectilux but I wanted to find out if that's a characteristic of both, or just the RF.

Quite normal...at least from my experience with DNA or any diopter for that matter. Oval bokeh stretch is often increased. It can be a good trade off when closing down on taking lens to retain sharpness on many scope lenses, since the apparent oval defocus is then reduced to a more 'regular' looking stretch ratio, akin to shooting with the taking lens with an open aperture when no diopter is used. 

Since most modern cameras perform very well at higher iso's...the effective loss of light by stopping down is far less of an issue.

For example, Ive found f4 - f5.6 on Core DNA gives a comparable oval defocus stretch value to having the taking lens set at f2 - 2.8 when no diopter is up front. From most single-element diopters I've tried  - I'd say f4 is as wide as you'd want to be to help avoid funky glows and highlight ghosting when used in front of most scope lenses....there is still plenty of defocus stretch, due to the diopter 'effect'.

My advice to anyone using any of the vari-diopter solutions is to stop down 2-3 stops more than you would normally...so as to give the single-element optics a fighting chance at resolving sharpness, without ugly highlight edge artefacts...there will still be plenty of shallow depth of field for those who crave it.

 

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3 hours ago, Hans Punk said:

Quite normal...at least from my experience with DNA or any diopter for that matter. Oval bokeh stretch is often increased. It can be a good trade off when closing down on taking lens to retain sharpness on many scope lenses, since the apparent oval defocus is then reduced to a more 'regular' looking stretch ratio, akin to shooting with the taking lens with an open aperture when no diopter is used. 

Since most modern cameras perform very well at higher iso's...the effective loss of light by stopping down is far less of an issue.

For example, Ive found f4 - f5.6 on Core DNA gives a comparable oval defocus stretch value to having the taking lens set at f2 - 2.8 when no diopter is up front. From most single-element diopters I've tried  - I'd say f4 is as wide as you'd want to be to help avoid funky glows and highlight ghosting when used in front of most scope lenses....there is still plenty of defocus stretch, due to the diopter 'effect'.

My advice to anyone using any of the vari-diopter solutions is to stop down 2-3 stops more than you would normally...so as to give the single-element optics a fighting chance at resolving sharpness, without ugly highlight edge artefacts...there will still be plenty of shallow depth of field for those who crave it.

 

Thanks! Great info.

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9 hours ago, AaronChicago said:

This thread may be helpful for me. I just got the Rangefinder to use with my Takumar 50mm and Singer 16D. I did some testing with/without the rangefinder and the background is stretched vertically by quite a bit with the RF. Is that normal? It's rather odd looking compared to the "anamorphic only" footage. I can still return it and get the Rectilux but I wanted to find out if that's a characteristic of both, or just the RF.

Good choice in taking lens, I've found that Super Taks are a great sharp taking lens with Anamorphics.

As far as the extra stretched background, that's a bonus - oval out of focus areas is why a lot of us use anamorphics (Yes, it's not the flares! You get over them very quickly once they ruin a great shot & by ruin, I mean obscure what you really want people to be looking at, & yes that's not the flares).

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9 hours ago, Bioskop.Inc said:

Good choice in taking lens, I've found that Super Taks are a great sharp taking lens with Anamorphics.

As far as the extra stretched background, that's a bonus - oval out of focus areas is why a lot of us use anamorphics (Yes, it's not the flares! You get over them very quickly once they ruin a great shot & by ruin, I mean obscure what you really want people to be looking at, & yes that's not the flares).

Yeah I agree with oval bokeh and totally out of focus areas, but this is the entire frame, including the parts that are partially in focus. Everything except the dead center.

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1 hour ago, AaronChicago said:

Yeah I agree with oval bokeh and totally out of focus areas, but this is the entire frame, including the parts that are partially in focus. Everything except the dead center.

The way that you've written this sounds like it is a problem, can you throw up an image or 2?

One thing that the Super Taks are renowned for is their thin plane of focus when wide open, but am assuming that this isn't the case....

Also, as Hans said, Diopters will introduce more distortion to the anamorphic qualities & this can produce an overly soft extra-stretched effect. Good quality diopters (doublets, not singlets) tend to control this more, but can still be present. 

I've found this to be a problem & now now tend to use longer taking lenses with my Iscorama, when i want to do close-ups etc... I also find getting too up close & personal with real people can be off putting for everyone concerned - objects don't get put off!

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Hey Sketch, do you have a picture of your rig? How do you like the Mini 4.6K so far?

By the way, I downloaded your shots from Flickr, and when viewed in full res I can see a vertical line pattern embedded in the image. Is that visible in the source files as well? What format where you shooting in?

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Hi Liszon, thanks for reminding me to change my privacy settings on Flickr.  Those stills are from an unreleased project and I should try to prevent quite so many stills from being downloadable.

There's some FPN in some of the images from the Ursa Mini 4.6K where I pushed the sensor pretty hard.  I can clean it up, but I just did a super quick grade for those stills until the director sits down with the colorist.  

Shooting in 4:1 compressed raw.  No images of the camera build, but it's pretty standard, rails, lens supports and lenses.

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