What causes this mess? Strange colour casts on IQ180 back shots.

[rogerxnz]

Can anyone explain these shots which are from a series of about ten taken in bright sunlight at 50 ISO on a Linhof Techno with a Rodenstock 40mm lens at about 1/8 sec at f11. I used a Kapture Group one-shot cable to release the shutter. Battery was good. Temrature was about 15º C.

One shot is of the subject. the other is with a LCC plate at 4x exposure. Most of the ten show weird casts as well.

I didn't think of trying another lens at the time but moved to a different location and had no trouble with a 60mm lens. I swapped back to the 40mm and got five OK shots. Then the next two had strange casts as well.

The lens couldn't cause this problem could it?

The back is under warranty and I will be communicating with the dealer.

Any ideas?
Roger

Update: The solution has been found. See my post at the end of the thread.
Roger

[Paul2660]

Hello Roger

I assume the lens is the 40mm HR-W Rodenstock?

If so were you shooting into the sun or at an angle where the sun was able to hit the front of the lens.  The reason I ask is that the top example shows the classic flare that the 40mm can get when exposed to the sun, where the front element of the lens is being exposed to rays of the sun.  The 40mm can have terrible problems with sun flare, and can get a large red center flare.  The top shot seems to shot this, but not sure about the yellow on the LCC. 

I use the 40mm quite a bit on an IQ260 but always have the Lee wide angle hood installed.  Even then I have to watch the angle of the sun as sometimes I get the flare issues.

I recently read about another photographer who sent his 23mm back to Rodenstock and they recoated it, and that reduced the flare issues that his 23 HR had.  Not sure if they had to totally pull the lens apart, but I assume they had to.  My recent history with Rodenstock high cost glass, I would not want them pulling my lens apart.  But I am probably an exception.

The 40mm will give the center flare and can ghost even with the sun behind you, however it's not as bad as the 90mm HR, which is terrible for this (ghosting).

I personally don't feel it's your back, especially if the 60mm worked OK. 

Paul Caldwell

[Bart_van_der_Wolf]

Any ideas?

Hi Roger,

Judging from the LCC pattern, it looks like sensor calibration data is missing. I'm not familiar enough with your back to know how that could be or how to fix it, sorry.

Cheers,
Bart

[Chris Barrett]

My guess was lens flare as well.  The mural side of the building is def in shadow, so the sun must have been coming at you.  I never shoot architecture in shadow, so I don't really run into this, but I also use the Lee WA hood.

[yaya]

Roger,
If the same lens works ok at faster shutter speeds (like 1/60 or faster) then the Copal shutter needs service.
This is based on you saying that the 60mm works ok and that the issue is intermittent.

BR
Yair

[rogerxnz]

Hi, Paul
Yes it's the 40mm HR-W Rodenstock. Well spotted!

The sun was at 90º to the wall, coming from the right of the scene. I was aware that sun could be hitting the lens and some of the shots were taken with a Lee WA hood on. Those shots also had a polarizer (because I cannot unscrew it from the holder!). I also put a black filter pouch over the (empty) glass filter slot at the top of the hood.

None of those steps seemed to make much difference.

Because I thought the problem was back-related (after taking all the above steps), I did not test another lens. At the next location I rotated the camera and took random shots at various angles. Two exhibited the same problem and I cannot recall whether I had the hood on or not. They are attached and were taken also at about 90º to the sun which was coming from the left of the frame. You can see similar ghosting.

None of the other shots in the sequence show ghosting.

So, now that I know it is not the back, I will test the lens more to see what I have to do to avoid the problem.

How does one find out about this ghosting problem? I'm amazed it can happen with the sun behind you.

I am also surprised you say it occurs with a RS 90mm lens. Is that the new very expensive one? A lens in that range is the only missing item from my kit. Is there a 90 lens which is less likely to flare?

Thank you for your help.
Roger

Hello Roger

I assume the lens is the 40mm HR-W Rodenstock?

If so were you shooting into the sun or at an angle where the sun was able to hit the front of the lens.  The reason I ask is that the top example shows the classic flare that the 40mm can get when exposed to the sun, where the front element of the lens is being exposed to rays of the sun.  The 40mm can have terrible problems with sun flare, and can get a large red center flare.  The top shot seems to shot this, but not sure about the yellow on the LCC.  

I use the 40mm quite a bit on an IQ260 but always have the Lee wide angle hood installed.  Even then I have to watch the angle of the sun as sometimes I get the flare issues.

I recently read about another photographer who sent his 23mm back to Rodenstock and they recoated it, and that reduced the flare issues that his 23 HR had.  Not sure if they had to totally pull the lens apart, but I assume they had to.  My recent history with Rodenstock high cost glass, I would not want them pulling my lens apart.  But I am probably an exception.

The 40mm will give the center flare and can ghost even with the sun behind you, however it's not as bad as the 90mm HR, which is terrible for this (ghosting).

I personally don't feel it's your back, especially if the 60mm worked OK.  

Paul Caldwell

[rogerxnz]

Lens flare seems to be the cause but, as stated above, the sun was at 90º and slightly behind me.

I need to do more testing.

My guess was lens flare as well.  The mural side of the building is def in shadow, so the sun must have been coming at you.  I never shoot architecture in shadow, so I don't really run into this, but I also use the Lee WA hood.

[rogerxnz]

Hi, Yair
That's an interesting idea. Would you mind explaining the theory behind it.

Lens flare seems to the more likely cause (although I did try to avoid it) but I will test higher shutter speeds also. The fastest I used on the day was 1/30th.

Thank you
Roger

Roger,
If the same lens works ok at faster shutter speeds (like 1/60 or faster) then the Copal shutter needs service.
This is based on you saying that the 60mm works ok and that the issue is intermittent.

BR
Yair

[Chris Livsey]

I can't see how flare is going to result, as in those last examples, of half the sensor showing them with a straight line cut off.
I suspect this is tied up with the shutter and the back latency settings.

Supported shutters in poor condition can cause image quality problems such as streaking or blurring at long exposure times, "Two Shot time-out" errors or other image quality and capture problems.

https://www.phaseone.com/en/Search/Article.aspx?articleid=1573&languageid=1
https://www.phaseone.com/search/article.aspx?articleid=1775&languageid=1

As ever the shutter will not consistently repeat its error so user testing may not be sufficient.

[Paul2660]

I looked at the crops again and I agree the hard line going across the image seems more like a back calibration issue.

I was looking at the red blob on the first post and missed the hard line in the center.  From problems I have with my phase backs where you get the hard line separation tends to have a calibration issue.

Don't know if the shutter could be causing this or not.

With my backs, when I started to see this type of problem I would get it with any lens on my tech camera and air of my Mamiya lenses.   If you are getting it with only the 40mm it very well may be the shutter not in time with the back.

The ghosting when I get it tends to show up as an area of less contrast and seems hazed out.

Paul

[rogerxnz]

Because the problems seem to occur only when the sun is at approximately 90° to the lens' axis, would that not rule out back calibration and shutter issues?

In any event, what is "back calibration" and how do I get it! Apologies for my ignorance.

The latency setting on the back is probably not causing the problem because I have not changed it since I got the back and it works OK with other lenses.
Roger

I looked at the crops again and I agree the hard line going across the image seems more like a back calibration issue.

I was looking at the red blob on the first post and missed the hard line in the center.  From problems I have with my phase backs where you get the hard line separation tends to have a calibration issue.

Don't know if the shutter could be causing this or not.

With my backs, when I started to see this type of problem I would get it with any lens on my tech camera and air of my Mamiya lenses.   If you are getting it with only the 40mm it very well may be the shutter not in time with the back.

The ghosting when I get it tends to show up as an area of less contrast and seems hazed out.

Paul

[Doug Peterson]

Almost certainly a mechanically lagging shutter.

The shutter remains open after the flash sync signal has indicated the exposure is over. This messes with the generation of the black calibration file.

You can check by detaching the flash sync port and initiating/ending the exposure using a wakeup cable and fire the mechanical shutter while the back is exposing. The issue should never happen when you are 100% sure the lens fully closed before the back stopped exposing.

Your dealer should know the best place/way for you to have a copal shutter repaired/tuned-up.

(all as Yair indicated previously, just with a bit more elaboration on his behalf)

[buckshot]

Is there a 90 lens which is less likely to flare?

The Schneider Apo Digitar L 4.5 / 90mm would be a safer bet, but it 'only' has a 90mm image circle compared to the R/S's 125mm, and isn't as sharp (if you're a pixel-peeper).

It's not a retrofocus lens so there are far fewer elements / groups for extraneous light to bounce around on and through.

[rogerxnz]

Thank you, Doug, for the explanation but it seems to me that, if the problems only occur when the sun is at about 90º to the lens' axis and the shots taken at other angles to the sun are OK, the problem cannot be with the shutter.

As mentioned above, I rotated the camera 360º taking shots at random angles to the sun. My second group of two images above are the only ones of about six that show the problem and they were taken at what seems to be the problem angle.

Also, on the day before, i used the same lens on the same subject and had not problems. The only difference was that on the previous day, there was no direct sun as the sky was overcast.

I will test angles and shutter behaviour again.
Roger

Almost certainly a mechanically lagging shutter.

The shutter remains open after the flash sync signal has indicated the exposure is over. This messes with the generation of the black calibration file.

You can check by detaching the flash sync port and initiating/ending the exposure using a wakeup cable and fire the mechanical shutter while the back is exposing. The issue should never happen when you are 100% sure the lens fully closed before the back stopped exposing.

Your dealer should know the best place/way for you to have a copal shutter repaired/tuned-up.

(all as Yair indicated previously, just with a bit more elaboration on his behalf)

[calindustries]

I've seen issues like this with broken shutters on both p65 and credo40 backs. the broken blades stayed open. Doug explained better what actually happens but the files looked very similar....

[eronald]

This is a back/shutter sync issue, as Doug says.
Now is the time for your wonderful dealer to show his worth ...

Edmund

[rogerxnz]

Thank you for this. I have some testing to do but I presume you mean the lens dealer???
Roger

This is a back/shutter sync issue, as Doug says.
Now is the time for your wonderful dealer to show his worth ...

Edmund

[Chris Livsey]

Thank you, Doug, for the explanation but it seems to me that, if the problems only occur when the sun is at about 90º to the lens' axis and the shots
Roger

Coincidence can play strange tricks and the shutter may be affected physically when moved to change the angle.

[rogerxnz]

When I got home this evening, i looked at the shutter in the 40mm lens and it seems to work fine with no hanging or delays.

Then, I looked at the camera itself and noticed the bellows were not properly installed at the rear standard on the side that faced the sun in the first pair of shots. There was a gap of about 3mm at the bottom corner!

That seems to be consistent with the advice that the casts were caused by light reaching the sensor during the calibration of the black file.

I'll check when I have time but it seems more likely that light got in through the gap in the bellows. I'm pleased because that is a very fixable problem and I don't have to send lenses or backs overseas for investigation and repair.

Thank you all for your help.
Roger