RAW Format Advice Needed

[RonFrank]

I said to keep it as light as possible without blowing it out.


Nope I mean overexposing the image. A digital camera unlike film is a linear device. It’s response to light is linear. So lets take this simplified example. Your digital camera can only capture 4096 shades of gray. 4096 is white and 0 is black. Each block is a stop in exposure.

Let's skip the confusing and rather incorrect (or at least very incomplete) example of how digital sensors capture light.

The fact is one does NOT want to OVEREXPOSE the image, but rather PROPERLY expose the image. However with digital if you MUST ERROR in one direction, OVEREXPOSURE is a BIG mistake.

Photosites are sensitive to blooming. Blooming is when a photosite collects so much light it overflows into adjacent photosites. Light mixture is an additive process. While mixing paint together is subtractive, and mixing Red, Blue, and Green will make black, as you combine colors of light, you end up with white.

Those are two very good reasons why detail can often be saved in an image that is UNDEREXPOSED in a digital process, but it's next to impossible to get detail in an overexposed image, it is just NOT there.

The bottom line is that digital photography is NOT forgiving to overexposure. I compare digital to shooting slide or positive film, vs. shooting negative file. Under exposure in negative film is death, and overexposure in slide film is death.

My BEST advice is to learn how to use a histogram to judge an exposure in camera after an image is made, and then adjust the exposure based on the results to fine tune.

Realize that digital camera's have what is called exposure latitude, and it is NOT possible to shoot a scene in full sun with bright highlights combined with deep black shadows without clipping one end of the spectrum. Camera meters are reflective based systems, and are easily fooled which is the reason why a histogram is a MUCH better way to judge exposure.

Ron

 

[crestgel]

Well put. about the camera raw and tag files. I agree the histogram is very important, understanding it is more important.

Let's skip the confusing and rather incorrect (or at least very incomplete) example of how digital sensors capture light.
It is a simplified example,

It was meant to be a simplified example, not a How Things Work Article. No wonder why you are confused.

So lets take this simplified example. Your digital camera can only capture 4096 shades of gray. 4096 is white and 0 is black. Each block is a stop in exposure.

I disagree with your assertion of overexposure being improper I may not have explain it clearly so here is a links to more info on this.

http://luminous-landscape.com/tutor...ose-right.shtml

Semantics maybe the problem. I call it over exposure you call it correct exposure. I find that I often need to overexpose an image after I see the histogram. I have to overexpose so overexposing it is my PROPER exposure.

The bottom line is that digital photography is NOT forgiving to overexposure. I compare digital to shooting slide or positive film, vs. shooting negative file. Under exposure in negative film is death, and overexposure in slide film is death.

Ansel Adams would meter with a spot meter (reflective meter) on an area that he wanted to be dark with detail and stop down 2 (underexposing) with BW negative film

Oh no Ansel Adams made a big mistake! He underexposed his negative film. The truth is that he did not make a mistake. Google Zone System and find out why.

If the word overexposure is the problem then please replace it with PROPER exposure or better yet EXPOSE for the brightest part of your image being careful not to clip it.


Underexposing digital images and then trying to get it back has its drawbacks. You may be able to get some information back from the dark areas but they often look pixilated, abrupt tonal separations. This is why you expose PROPERLY to the right of your histogram.

Yes the dynamic range of a scene may require clipping. If possible bracket the exposure. If not then decide on what you want to keep. The is also true with film too.


All RAW files are linear files. They are dark and flat. The reason why they look good when you open it in your RAW converter/program of choice is because of the application of tagged shooting information, linear conversion, tone curve that...

 

[Scubatooth]

crestgel i think out main difference is in how we view what is the correct exposure you would say over expose as where i would want it correct to start. For me i try to get my histogram so that my whites are there but not blown out unless i cant help it (shooting at high noon). then if im shooting a image were i have a 5+ stop range i will do a 2 or 3 shots(bracket) to get the various items i need then i will layer them for the final product.



the zone system comparison wont work for digital as the sensors dont see the image the same as a negative film, digital is closer to a slide film. in addition to this you can always play with the processing of a neg or slide to alter the denisties of various areas as has been mentioned by ron.

RAW isnt very linear as i can introduce custom tone curves into the image before its processed. They arent flat either because they are the same as the image if shot in jpeg or tiff its just that you have more options when converting the image if you missed. for me i rarely make changes outside of the conversion process except for output sharpening before i print them image. heavy editting in PS is usually reserved for images im really trying to save or that i have been sent and have to edit because they have to be used.

FWIW

Tooth

 

[crestgel]

crestgel i think out main difference is in how we view what is the correct exposure you would say over expose as where i would want it correct to start. For me i try to get my histogram so that my whites are there but not blown out unless i cant help it (shooting at high noon). then if im shooting a image were i have a 5+ stop range i will do a 2 or 3 shots(bracket) to get the various items i need then i will layer them for the final product.



the zone system comparison wont work for digital as the sensors dont see the image the same as a negative film, digital is closer to a slide film. in addition to this you can always play with the processing of a neg or slide to alter the denisties of various areas as has been mentioned by ron.

RAW isnt very linear as i can introduce custom tone curves into the image before its processed. They arent flat either because they are the same as the image if shot in jpeg or tiff its just that you have more options when converting the image if you missed. for me i rarely make changes outside of the conversion process except for output sharpening before i print them image. heavy editting in PS is usually reserved for images im really trying to save or that i have been sent and have to edit because they have to be used.

FWIW

Tooth

I hear what you are saying. I think that the word overexposing is the problem.

Here is another way of looking at it. I take a shot with my DSLR camera. After looking at the histogram I decide is is underexposed so I add a stop of light and make the PROPER exposure.

My Ansel Adams example is not to say that negative film and digital cameras are the same. The point I wanted to show is that under or over exposure is not such a taboo thing to do. It was also used because the previous post said that underexposing negative film is death.