Porthole effect over wider lenses

[Emanuel A.]

Although a common hassle comprehending any acquisition device, it seems there's something we should care about. Unless you have a RED ONE to test on.

I've been warned about a potential porthole effect over wider lenses (even a Zeiss with Super35 coverage) though minimized if stopped down (despite a potential vignetting then).

Having been tested Zeiss Standards on a Phantom HD, the 16mm was OK from T4 & the 24 OK from 2.8-4 split, according a reliable source.

So, granted that a Phantom HD has a larger sensor area (comparing with the RED sensor's 22.2 x 12.6 format) from this info published here (@3rd paragraph):

http://www.visionresearch.com/index....=camera_HD_new

«The HD has allocated formats for standard HD 16:9 (1920 X 1080 pixels) and 35mm mopic at 1.85:1 using an active pixel area of 25.6mm x 13.85mm (2048 X 1108 pixels) making this camera fully compatible with all 35mm equipment as well.»

...can we infer the issue shall be less noticeable with the RED ONE ? Or is the difference barely significant at the wider end with a 16mm lens, for instance?


Any thoughts?

Mostly from the RED Team who have been testing the prototypes
[BTW, when on the PJ movie Zeiss Standards were used for some shots!]

[Stephen Williams]

Hi Emanuel,

Using Zeiss Standards on a Phantom HD:-The portholing wide open was a big issue, a small circle in the center of the frame was much brighter than the edges. When stopped down the frame became even. My Nikon D70 with the supplied lens portholes when wide open, very obvious on a white background. Most Zoom lenses will porthole to some extent when wide open, obvious if you have a video camera & a vectorscope.

When lenses have a small exit pupil, the light may not travel in a straight line, film does not care what angle the light hits it. A CCD or CMOS sensor does!

Stephen

[Don King]

Gold information here (an exception during this silly season?)

[chuck colburn]

Anyone know if there are those circular graduated n.d. filters made in larger sizes?
Use to see them for medium format cameras using wide angle lenses. I think they use to include one with the 30mm lens for the Hassy Xpan also.
Anyhow it could be answer to the problem with wide angles shot at fast stops.

[Wade McDonald]

[BTW, when on the PJ movie Zeiss Standards were used for some shots!]

Just a little FYI, at NAB Jim said that the PJ short was shot with Cooke S4/i primes and an Angenieux Zoom, not Zeiss.

W

[Stephen Williams]

Just a little FYI, at NAB Jim said that the PJ short was shot with Cooke S4/i primes and an Angenieux Zoom, not Zeiss.

W

Hi,

A crew member informed me his Zeiss Standards got an outing.

Stephen

[Emanuel A.]

Yeah, Jim told me so. I had taken the information from Stephen but I also could check and it is spread all over the website:

http://www.reduser.net/forum/showthread.php?p=31172#post31172

http://www.reduser.net/forum/showthread.php?p=30336#post30336

It had been better to stand corrected there when it was posted. Although if too much later, it may result in unwanted misinformation.

[Petros Nousias]

Either my understanding of the language is not that great or the question remains unanswered. Is there a porthole problem with the standard primes or not?

[Emanuel A.]

No Petros, it isn't anything about that piece of glass. It's only a problem with (all wide) "film" glass converted to "electronic" glass. Only with wides at open apertures. Closing the aperture shall give vignetting. But if you will shoot 1:2.35/2.39, I believe you shall have the problem solved since the vignetting comes up only to the corners. Or am I missing something Stephen? (he's the man to answer this sort of issues -- reduser.net gold even if he may think this is not his home... :innocent:)

[Stephen Williams]

Either my understanding of the language is not that great or the question remains unanswered. Is there a porthole problem with the standard primes or not?

Hi,

I have not had a chance to test a Red one. However I am 99% certain that 16mm & 24mm Zeiss Standard 2.1 lens will porthole when wide open.

The size of the exit pupil is the issue here, Zeiss Superspeeds probably won't have the problem. This accounts for the absurdly high prices people will pay for those lenses that were designed 30 years ago.

As Zeiss Standards are very small (& expendable) relative to Cooke S4's or the Arg. zoom lens I think there is every possibility that Zeiss Standards were used for some shots.

Stephen

[astro]

Just to clarify, the lenses used on the shoot were a set of Cooke S4's , 24-290mm Optimo,17-80mm Optimo(for aerials and crane) and a set of Zeiss standards (T-2.1).
The only reason the standards were used was because we didn't have another set of S4's. There were occassions when the two cameras were separated from each other and needed their own set of primes.
The shoot was put together in an extremely short time frame, and the gear was ordered on the bases of availabilty and convenience. Simple as that.

Andrew Stroud.

[Emanuel A.]

The size of the exit pupil is the issue here, Zeiss Superspeeds probably won't have the problem.Do you think so? Why?

[Emanuel A.]

Just to clarify, the lenses used on the shoot were a set of Cooke S4's , 24-290mm Optimo,17-80mm Optimo(for aerials and crane) and a set of Zeiss standards (T-2.1).
The only reason the standards were used was because we didn't have another set of S4's. There were occassions when the two cameras were separated from each other and needed their own set of primes.
The shoot was put together in an extremely short time frame, and the gear was ordered on the bases of availabilty and convenience. Simple as that.

Andrew Stroud.Thank you for your input. An useful enlightenment, informative enough. Moreover, I have two questions:

1) Portholing with open apertures and vignetting closing the aperture at wide? If so, which focal lengths?

2) Color matching issues between the lenses from distinctive brands?

EDIT -- Well, generally speaking though I open my focus over the Zeiss standards (T2.1).

Thanks.

[RobRoySyd]

The backfocus distance is also a factor, the further the rear element of the lens is from the focal plane the higher the angle the light strikes the focal plane and hence less risk of portholing. It could sure be an issue with some of the wide 35mm stills lenses, the ones where you had to lock the mirror up becuase the rear element had to get so close to the film.

[astro]

[QUOTE=Emanuel;45682]Thank you for your input. An useful enlightenment, informative enough. Moreover, I have two questions:

1) Portholing with open apertures and vignetting closing the aperture at wide? If so, which focal lengths?

We were composing for 1: 2.35 aspect ratio so generally any vignetting to be had at T-2 would most probably become apparent in the corners of the "full gate" area. To be honest its not somthing we had time to think about or consider. I couldn't say which standards would be a problem at T-2, its been a while since I've worked with them on a super 35mm shoot. From memory I can't recall them being a problem though. Some one else may have more information. The best way to find out is to test for your self.

2) Color matching issues between the lenses from distinctive brands?

That wasn't a consideration, it was all about getting what equipment was available.

Its safe to say the S4's and the Optimo's resolve much better than the Zeiss standards do but I would imagine it would be pretty hard to pick out the lenses from shot to shot in the film. The shots using the standards were few and most of the film was shot on the S4's and Optimo's.

A.

[Petros Nousias]

Would any member of the red team care to comment? Im asking because I recently purchased a 10 lens 2.1 set to be used with red and wonder whether it was a bad decision. Of course I had no idea about the porthole effect till this thread began.

[Emanuel A.]

I started up this one 'cause the same purpose than you, Petros though I hadn't bought it yet.

Actually, I've been in touch with Jim on subject and a lens coverage recommendation over a 30mm image circle has been coming from him. Stephen gave the 1st information on portholing. I posted 'cause I thought it would be important for some of us, if not for all. This is a community, right? -- IMHO, if we can get it as the best one, we must contribute to the best enlightenment and fortunately we've had good contributors!

This Andrew's input over the Zeiss Standards: «I couldn't say which standards would be a problem at T-2, its been a while since I've worked with them on a super 35mm shoot. From memory I can't recall them being a problem though.»

...is a very promising hint though. So be cool, Petros! With luck you should be fine. :sorcerer:

And it comes up a good add to the previous Stephen's experience over the Phantom HD despite otherwise.

However, Matt Uhry (one of the most coolest UNBIASED DPs that I could find over these same boards) has been warned myself on subject:

«The Zeiss 2.1's especially the 16mm and the 24mm may have problems, you would want to test them out before buying a set. It's not because they don't cover enough area but because the light coming from the rear of the lens strikes the film or sensor at a oblique angle. This does not matter on film emulsion, but is not good on an electronic sensor.»

I just can't be sure if this quote from Matt succeeded the Stephen's finding or his own (from Matt himself).


EDIT -- Although it seems the problem may affect only the wide angle ones but the 16 - 24 range probably. Not the 35mm (or even the 28mm) focal length(s) or am I wrong?

[Stephen Williams]

Do you think so? Why?

Hi Emanuel,

Superspeeds have a large exit pupil!

Zeiss Standards & Cooke S2/3 have an issue with P+S adapters, I was fairly sure there would be issues with a digital sensors. That's why I tested the Zeiss on the Phantom

Stephen

[Gordon Prince]

Post deleted. Wrong thread.

[Stephen Williams]

This Andrew's input over the Zeiss Standards: «I couldn't say which standards would be a problem at T-2, its been a while since I've worked with them on a super 35mm shoot. From memory I can't recall them being a problem though.»

...is a very promising hint though. So be cool, Petros! With luck you should be fine. :sorcerer:



Hi Emanuel,

The Zeiss Standards will cover S35 no problem when shooting on film. The wider 2 will with 99% certainty porthole @T2.1 on any digital sensor.There was no 35mm in the set that I tested, however the 50 & 85 had no problem.

Stephen

[Emanuel A.]

Thanks Stephen! Your contribution has been quite helpful but you actually well know as gold member as you already are. It would be interesting to check the 28mm behaviour though.

[Stephen Williams]

Thanks Stephen! Your contribution has been quite helpful but you actually well know as gold member as you already are. It would be interesting to check the 28mm behaviour though.

Hi Emanuel,

You mean 35mm! I did not buy the Phantom HD, so I don't have a single chip camera to test with, that is until I get my hands on a Red!

Stephen

[Emanuel A.]

Well, Stephen, it seems there's no 28mm focal length at Zeiss Standards series, correct? But it would be interesting to know if higher than 24mm, the same would occur or not. Since you check it would be OK T2.8 - T4 split.

I have an offer over a 18mm T3.2 (not Zeiss), can I expect it should be fine at T4?

[Now, off topic]

Didn't you think to buy a cheap single CMOS chip camera like the new Canon HV20 just in order to check this sort of issues? (I will!)

BTW, take a look over this:

http://www.reduser.net/forum/showthread.php?t=2563

It fully worths the glance.

[Petros Nousias]

Actually there is a 28mm. the full set is something like this:10mm, 12mm, 16mm, 20mm, 24mm, 28mm, 32mm, 40mm, 50mm, 85mm, 100mm, 135mm, 180mm.

[Stephen Williams]

Actually there is a 28mm. the full set is something like this:10mm, 12mm, 16mm, 20mm, 24mm, 28mm, 32mm, 40mm, 50mm, 85mm, 100mm, 135mm, 180mm.

Hello Petros,

There is no 28mm in the Zeiss Standard T2.1 Range. The range you are quoting are the Zeiss Ultra Primes. The Ultraprimes have nothing in common with the lenses being discussed in this thread. (OK they are both made of glass):)

Stephen

[Stephen Williams]

Well, Stephen, it seems there's no 28mm focal length at Zeiss Standards series, correct? But it would be interesting to know if higher than 24mm, the same would occur or not. Since you check it would be OK T2.8 - T4 split.

I have an offer over a 18mm T3.2 (not Zeiss), can I expect it should be fine at T4?

[Now, off topic]

Didn't you think to buy a cheap single CMOS chip camera like the new Canon HV20 just in order to check this sort of issues? (I will!)

BTW, take a look over this:

http://www.reduser.net/forum/showthread.php?t=2563

It fully worths the glance.


Hi Emanuel,

The only way to know if that 18mm lens will work on a digital sensor is to try it on a RED, Phantom or D20. Guessing does not help here.

The chip of the HV 20 is to small to help.

Stephen

[Emanuel A.]

I see... Thanks!

[Petros Nousias]

Actually I own a Zeis T2.1 MkII 28mm, its just that its not that common(usually the set is 16, 24, 32, 40, 50, 85, 135)

[Stephen Williams]

Actually I own a Zeis T2.1 MkII 28mm, its just that its not that common(usually the set is 16, 24, 32, 40, 50, 85, 135)

Hi,

Does it porthole on a digital sensor?

Stephen

[Petros Nousias]

The porthole effect is very new to me and I have no idea whatsoever. Thats why I asked before and really hope it doesnt happen with the 28 as well(I also have a 16, 20 and 24).

[Stephen Williams]

The porthole effect is very new to me and I have no idea whatsoever. Thats why I asked before and really hope it doesnt happen with the 28 as well(I also have a 16, 20 and 24).

Hi,

You may get an idea by looking through the lenses backwards, if the 'hole' on the 28 is bigger than the 24 you may be in luck.

Stephen

[Jarred Land]

Just so you guys know.. we used the Zeiss 14mm for one of the milk girls shots, and that 14mm is used for calibration in the lab almost every day between f2.8-f4 , and we never have had a problem. Your going to get natural fall off of course to a miniscule degree.. but nothing like "a porthole"

[Stephen Williams]

Just so you guys know.. we used the Zeiss 14mm for one of the milk girls shots, and that 14mm is used for calibration in the lab almost every day between f2.8-f4 , and we never have had a problem. Your going to get natural fall off of course to a miniscule degree.. but nothing like "a porthole"

Hi Jarred,

Was that a Zeiss Standard T2.1 or an Ultraprime T1.9?

Stephen

Edit the effect is most obvious on a white background

[Emanuel A.]

Good question Stephen! And thanks chief for your help! -- I know you're a busy man but a good fellow too! ;-)


Your going to get natural fall off of course to a miniscule degree.. Up to? From what aperture can we go fully OK according your 14mm lens experience(s) with the RED prototypes' sensor?