help me to understand "good rolloff as opposed to bad (Blown highlights)

jambredz

jambredz

Veteran
So i always hear and read how some cameras especially film that has a high DR handle blown highlights more gracefully than one without good DR. but what does that reeaallly mean? Do you guys have examples that u can put up side by side that will show me a good blown highlight as opposed to a bad one? i'd really like to see and understand the difference.
 
It depends on several things in my opinion.

How gradual it clips, how sharp it clips, and how soon it clips.

The longer it takes until clipping occurs is usually good. This also means it will likely be more gradual, seeming more natural. Finally, a slightly softer edge between information and no-information is nice. I like to use a classic soft, or pro-mist to give some subtle bloom to the highlights. It helps it not look so digital, which is notorious for treating clipping with no mercy.
 
jambredz said:
So i always hear and read how some cameras especially film that has a high DR handle blown highlights more gracefully than one without good DR. but what does that reeaallly mean? Do you guys have examples that u can put up side by side that will show me a good blown highlight as opposed to a bad one? i'd really like to see and understand the difference.
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Here's a characteristic curve given for an Ilford film. Which film doesn't matter, just that most follow this curve in some regard.

Notice the 'S' shape, and how low values and high values have a 'curve', along with a linear portion in the middle.

The 'shoulder' is the significant difference between 'film' and 'digital'. The sensors digital cameras used, do not have a 'shoulder', and as such will saturate 'quickly', rather than having a non-linear response, and 'gradually' reaching saturation.

Older films would actually 'reverse' with too much light, and would produce a 'solarization' effect... most modern films don't do that...

Anyway, a 'good' roll off allows for detail to be captured, but not lost. It may not have the contrast, because of the rolloff but the variation is 'detectable'... with film one could perhaps compensate for 'over exposure' by under developing, as the variation was recorded, and by reducing the developing time, that portion of the shoulder would remain within the limit of saturation.

I'm sure that some similar electronics could be made to do the equivalent to film, but it would be more complex. What I have seen is the use of two or more 'collecting' cells per unit 'pixel', with each cell taking on different amounts of light, thus when the data is process one or the other, or in some combination the light intensity is calculated in a stepwise approximation of the 'gradual' falloff.

2006210192201716.jpg
 
all very interesting...thanks for taking the time guys. I definately can dig the use of promist to bloom the highlights Ryan. You guys have any examples of what you consider good rolloff as oppose to bad that i can see?
 
I wrote a blog about this.. http://dslr4real.tv/index.php?option=com_zoo&task=item&item_id=56&Itemid=1

BLOWN highlights say white windows can look very cool and save you a fortune in the lighting required to control dynamic range

CLIPPED highlights look terrible, especially clipping one colour channell only

Nearly all of my stills work has blown highlights, but my D3 and Hassy still cameras roll to blown in a nice manner

As a general rule (of thumb) the larger the chip the nicer roll off

A camera with bad roll off often gradiates or rainbows as the image goes to blown, one with nice roll off (film, 16 bit MF camera) does not

All of these images has areas of 255/255/255 - do they look OK ?

02.JPG
 
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those are really nice Morgan. though i dont see the blown highlight in the last pic. I will read your blog ..thanks!
 
jambredz said:
those are really nice Morgan. though i dont see the blown highlight in the last pic. I will read your blog ..thanks!
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I think the first one is right, the second one has a little too much window (aesthetically to much white in the frame) the third one - I bet the wine glass is blown

really the first one is IMO a nice example of good roll-off

These are stills and I think you can do similar with the 5d in moton, the EX1 (IMO) tends to go a little horrible as it transits to white, kinda flouro egdes - bad roll off

S
 
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