Weird red results

The23rdman

The23rdman

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Dean
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I did a quick moody red and green gelled shoot for my Slipknot loving 12 year old nephew last night. The results are terrible though. Shot it with my nifty, which is the sharpest lens I have, and I allowed enough ambient light to focus by with ease, but the results are soft as crap.

I know the lens is fine, but this is something I've noticed when shooting with strong gel colours. Anyone know what is happening?
 
Click for 300dpi full size original. Straight out of camera and LR3 with standard settings.
 
Looks sharp to me :shrug:

The red speedlite looks a little close and too harsh and has blown some of his face, better ambient lighting or another clean speedlite would help also.
 
open up the channels and then go to the red channel and add unsharp mask it because red is not as sharp.
like this
4822736949_9294c1c6cc_o.jpg
 
I've looked at some of the other shots, and Chaz is dead right. I've some with the subject half in red and half in green and the green is tack sharp. Interesting experiment.

Steve, his face isn't blown at all, mate. It's damn red, but not blown.
 
The23rdman said:
I've looked at some of the other shots, and Chaz is dead right. I've some with the subject half in red and half in green and the green is tack sharp. Interesting experiment.

Steve, his face isn't blown at all, mate. It's damn red, but not blown.
Click to expand...

the reason is each colour is a different wave length and you can not focus all at the same time. think back to inferred file you have a mark on the lens where to adjust your focus point, I know red is not IR but its that end, if you understand...
 
the reason is each colour is a different wave length and you can not focus all at the same time.
Click to expand...

Could you elaborate on this a bit Chaz? I understand about wavelengths and different coloured light etc etc....... but I don't get the not focussing on them all at the same time? Is this specifically to do with gels and flash etc??????
 
Lynton said:
Could you elaborate on this a bit Chaz? I understand about wavelengths and different coloured light etc etc....... but I don't get the not focussing on them all at the same time? Is this specifically to do with gels and flash etc??????
Click to expand...

That would be my guess, though I'm a bit surprised it's as noticeable as you say (can't see much on screen). Some lenses are more prone than others, basically more simple designs - an 'apo' lens should be better (apochromatic).

In theory, it's impossible to get all colours to focus on exactly the same point but with a bit of clever optical design you can get very close. Most lenses are optimised around green, as that's in the middle and I think tends to be a slightly more common colour in many photographs.

Red is as far as you can get from green and it's obviously right at the end of the visible spectrum. The next step along the way is infrared, which requires all lenses to shift their focus point beyond the visible spectrum, hence the IR focusing mark.
 
Chaz Photos said:
the reason is each colour is a different wave length and you can not focus all at the same time. think back to inferred file you have a mark on the lens where to adjust your focus point, I know red is not IR but its that end, if you understand...
Click to expand...
The aspherical glas elements should take care of this, but these are usually only found in expensive lenses.

Hoppy works too much with microscopes! Why can't all photography lenses have the goodness of my 63x NA1.4 pan fluo apo with LD collar?

edit: well, must have been another forum member, never mind Hoppy ;)
 
Cistron said:
The aspherical glas elements should take care of this, but these are usually only found in expensive lenses.

Hoppy works too much with microscopes! Why can't all photography lenses have the goodness of my 63x NA1.4 pan fluo apo with LD collar?

edit: well, must have been another forum member, never mind Hoppy ;)
Click to expand...

You've lost me Mike!
 
HoppyUK said:
You've lost me Mike!
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Yes, my bad, I only checked your profile after posting and realised that I mixed up users. The "63x" (magnification) I described is microscope objective, which is corrected for a completely planar plane of focus, is almost free of chromatic aberrations and is optimised for fluorscent imaging. My special little friend also has a collar which allows for focus distant adjustments. Usually, microscope lenses are corrected for 0.17mm glas cover slips, but the correction collar (a fancy term for a switch) allows to image through much thicker surfaces (like cell culture dishes). And finally the numerical aperature (NA) describes how much light the lens gathers. We give nature a tiny nudge and use immersion oils with a high refractive index to encourage a little more light flowing through the optics.

Well, this has run a little off topic. Sorry Dean!
 
Bloody hell, what a thing to wake up too! I've posted a shot in the portrait forum which shows this in practice though. Green side sharp, red side soft.
 
The23rdman said:
Bloody hell, what a thing to wake up too! I've posted a shot in the portrait forum which shows this in practice though. Green side sharp, red side soft.
Click to expand...

This one http://www.talkphotography.co.uk/forums/showthread.php?t=246176

I think it does show some evidence of the misfocused red, but it's very slight. Not 100% sure on that TBH.

The main difference between the red and green sides is because of the colour filtering effect of the red gel, which has removed the reddish chequers on the shirt. Whereas on the other side the red element has been darkened by the green.
 
The23rdman said:
Bloody hell, what a thing to wake up too! I've posted a shot in the portrait forum which shows this in practice though. Green side sharp, red side soft.
Click to expand...
;)

It is a cool photograph. I like that the drumstick exactly separates the colour zones.

Coming back to the red channel. I believe human skin is pretty much devoid of red contrast information. So this might be the reason for the misfocused impression.
 
HoppyUK said:
This one http://www.talkphotography.co.uk/forums/showthread.php?t=246176

I think it does show some evidence of the misfocused red, but it's very slight. Not 100% sure on that TBH.

The main difference between the red and green sides is because of the colour filtering effect of the red gel, which has removed the reddish chequers on the shirt. Whereas on the other side the red element has been darkened by the green.
Click to expand...

Trust me, richard, at full res it's obvious the red side is much softer. It's like a slightly soft shot with a kit lens rather than nifty fifty.
 
Cistron said:
;)

It is a cool photograph. I like that the drumstick exactly separates the colour zones.

Coming back to the red channel. I believe human skin is pretty much devoid of red contrast information. So this might be the reason for the misfocused impression.
Click to expand...

Thanks. It's a lesson learnt anyway.
 
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