# histograms



## cougar (Jun 15, 2004)

pardon my ignorance, but what am I looking for in a histogram? and how do I read one?

I look at it 2D liek my fish finder....


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## grayfish (Jul 31, 2005)

cougar said:


> pardon my ignorance, but what am I looking for in a histogram? and how do I read one?
> 
> I look at it 2D liek my fish finder....


Here is one explination.

http://www.luminous-landscape.com/tutorials/understanding-series/understanding-histograms.shtml


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## Dances With Fish (Jul 24, 2006)

Well not to be a smart ***** but You didnt get the manual on your fish finder..???
Usually the phamplets and things we recieve with our electronics are best reference in cases like these....If your fish finder operates or indicates by way of histogram than it should be(likely to be) in your manual.....
Wish I could be of more service


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## RustyBrown (May 29, 2004)

*Great start...*

That's an excellent link, but let me just put it into a practical perspective. Your sensor has a dynamic range of tones it can record.

If you overexpose an image the graph will stack up against the right margian and you'll see that some of the data exceeded the brightness range of the camera with the settings used. This is what we refer to as blowing out the hightlights. This will show as pure white on the image and nothing can be done to fix it. Some displays will show blinking highlights on the image.

If you underexpose and image the graph will shift to the left. If there's data against the left margian then again data is lost and the overall noise level will be high.

*There is no such thing as a perfect histogram shape because contrast varies from image to image, but by not cutting off the data on either the left or right margains your exposures will always be good.*

Reviewing a display histogram is easier to do in bright light than trying to evaluate based on reviewing the image itself. Some images also will peg on both margins - an example would be shooting the opening of a railway tunnel from inside. The camera's meter wants to find the midline between light and dark and as a result you get a blown out white arch in the middle of the frame surrounded by black. There just too much range for the sensor to handle. That's what we use HDR for...but that's another story.


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## Pocketfisherman (May 30, 2005)

The thing to remember is that most cameras show the histogram of the RAW data after it is converted to JPEG. This means the data has gone through gamma conversion, which tends to compress the dynamic range at the top end of bright end of the tone range, and stretch the shadow range. When your camera display and the histogram spike near the right showing blown out highlights, they will show that way in the JPEG. But if you deal with RAW files, there is data there that can be recovered for increased dynamic range (1/2-1 stop) for Canons. So if you shoot raw, shoot so the histogram is weighted to the right end of the graph, and use the RAW convertor options for Shadow, Contrast, and Brightness to stretch the shadows and bring out shadow highlights on the bottom, and recover any highlights blown out. Unless you have a monitor with at least 700:1 contrast ratio though, forget all this as you won't be able to see it anyway.


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## Dances With Fish (Jul 24, 2006)

And I thought he was talking about the his. on his fishfinder...........What a goof


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## Saltwater Servitude (Mar 18, 2006)

http://forums.dpreview.com/forums/read.asp?forum=1020&message=22129907

Here's a link to some blown highlights so you can get a good idea of what Rusty is talking about. THese were recovered very nicely, but the DSLR in question is built for it.


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## cougar (Jun 15, 2004)

*ah, now I get it....*

thanks for the information and examples. It makes much more sense to me now. I knew what the flashing areas were in my camera LCD display, now I just have to be more mindful of my shooting settings. To be honest.... one problem I'm having with my PC monitor is calibrating it with my photo processor. Nothing like loving something on the screen for it to print horribly (well, not that bad....).


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## richg99 (Aug 21, 2004)

Poor man's monitor calibrator. Use a picture that you took and either printed by yourself.. or ....had printed where-ever you normally have your work printed. 

Load the original pix up onto your monitor. Hold the printed picture up next to the monitor. Adjust your monitor's settings until the monitor gives nearly the same tones, contrast, colors etc. that the printed picture does. Voila' this is as close as you are going to get without spending a lot of money on a real calilbrator. Rich


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## cougar (Jun 15, 2004)

Rich,


I think you were the one I got that idea from in the first place. Did that and the Mrs. complained that when she did her stuff, the monitor was too dark... Sounds like Goldilocks....

Anyways, I guess it's just all part of the learning process. In the end, I walk by places and think, "darn, I wish I had my camera...." So that's a good thing, right?

Thanks all! I think to accelerate my learning curve, I'll keep reading and maybe one day we can try to get together and do a show and do.....


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## richg99 (Aug 21, 2004)

Hmmmmm ***"and do a show""***** ANOTHER good idea is born on this group. 

Who is ready to step up and find a big, empty, air-conditioned space someplace? Maybe one of the fishing shops (Academy/FSU/Gander/BASS-Pro/Tops and Towers/Boat Dealers; Gun dealers... etc ) would find a side room for us. Say for a Saturday Morning...One/Two photos each from each member who is interested. Have to be outdoor related ( because of the sponsorship).

The show should provide extra foot traffic for the sponsoring store. What about sponsors here on 2cool already???

Who is a good organizer who has the time, connections and interest??? 

Rusty (our esteemed leader) MTStringer; Grayfish; Arlon??? Who is around the longest and knows his/her way around the area?


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