ART Official OTAP Noob-Resource Thread

charles foster kane

New Member
Feb 14, 2007
93,467
Croatia
This is the thread for when you just don't know whats going on but don't want to feel like a douche for asking in other threads. No question too noob, and hopefully some thorough and correct explanations in reply.

Absolutely NO replies of the :hsugh: variety.

Please keep discussion in this thread to a minimum. If you are going to post, please keep it generally confined to questions, answers to questions, clarifications, that kind of thing. Let's have some high quality EDU replies

Also, I'll pre-empt a bunch of questions by reminding people about Jcolman's awesome thread "Basic & Flash Photography 101" found here
 

Pikel

Active Member
May 25, 2003
186,476
PNW
I'll start. I don't know how to use a histogram. I have a rough idea what it represents, but I've never known how to utilize one to improve my photography, or why I should.
 

Marix

OT Supporter
May 23, 2006
27,969
You have two types of histogram: an overall luminance histogram, and a colour channel histogram. More about that later.

The axis are:
X axis = black at the left hand side, through to shadows, mid tones and highlights, then pure white on the right hand side. The extreme left represents pure black, and the extreme right is pure white. The scale is 0 to 255.

Y axis = The proportion of the image that is that bright, according to the X axis. I don't know the exact units, but a larger peak = more of that type of light/colour (more later).

A histogram is telling you how much of each type of light is in your image. It's probably the single most useful thing when it comes to reviewing an image you just took. Colours, white balance etc can be changed later, but a badly exposed image is much harder to correct. Zack Arias said he shot a whole wedding with 80% of the screen taped over and only the histograms showing to check exposure.

You can work out a lot about an image depending on the histogram.

An image where the histogram is larger towards the left contains a lot of black and shadow. It may be underexposed, or it may be correct, depending on the subject. A night time scene will have mostly shadows, with spikes of highlights (from streetlights, the moon etc)

And obviously an image with the majority of the histogram piled to the right contains a lot of mid tone and highlight. It may be overexposed, or correct.. a white wedding dress against a window won't have many shadows, but that isn't a bad thing.

You can also see the amount of contrast in an image. Something with a U shape has a lot of black shadow, less mid-tones and lots of highlights (i.e. high contrast). Something a ^ shape has a lot of mid-tone but less black/highlight. It is low contrast - again, not a bad thing necessarily.

If anything is touching the edges of the histogram, it is pure black or pure white. This is *generally* a bad thing.. these areas contain no photographic detail, but again it can be fine depending on your photograph or taste.

Colour histograms are a little more complex - you can split up the luminance histogram into blue, green and red channels. In sum, they total up to the luminance histogram. You can have a luminance histogram which looks fine, but you can blow out detail in colour channels, thus ruining the colour of an image - i.e. you have an area with pure green, red or blue channel. A summer field will have bright blues, darker greens etc, but the luminance histogram may average out in between and look low contrast. You have low *luminance* contrast, but still have colour contrast between green and blue.

A good guide of reading colour histograms is here:
http://www.kenrockwell.com/tech/yrgb.htm

Also, you can find a good guide to standard histograms here:
http://www.kenrockwell.com/tech/histograms.htm

Yes it's rockwell, but this is a straightforward guide with no bullshit.

Rockwell is only wrong about one thing. In modern digital cameras it is better to "expose to the right" - i.e. if you have a high dynamic range image (black shadows between trees but a really bright sky and white fence posts), it's better to slightly overexpose, so you can get some detail into those shadows. Then you can recover highlights in software. I can get 2 stops of recovery from my camera when in raw mode. Pikel, I think you have a d7k, which has the same sensor as me, so you should get two stops of recovery too. Older cameras can recover less.

Of course you can bring up black to get detail, but you will generate a lot of shadow noise.


Hope that was useful.. I'm sure cfk will chip in too, and we will overlap in some places and get some new info too :cool:
 

Pikel

Active Member
May 25, 2003
186,476
PNW
Yeah, I feel like I already understand color/data loss at the extremes and try to avoid it (and like using the highlights view to spot it sometimes).... a histogram is a neat representation of it but not sure I'd ever really use it. Hmm.
 
TS
TS
charles foster kane

charles foster kane

New Member
Feb 14, 2007
93,467
Croatia
should a light meter be aimed at the camera or at the light source?
I guess if you have a very dramatic, directional light you could point it at the source to make sure it catches the same amount of light as the subject, but for more soft light it probably wouldn't make much difference

Guessing you mean incident readings
 

tekniqs

Well-Known Member
Feb 20, 2007
9,464
i took a picture of my sister peeking outside the window. it's pretty bright on her face to the point where there really isn't much detail left...and then behind her is really dark....any advice on how to make her have detail while also lighting up the back a bit?
 

Marix

OT Supporter
May 23, 2006
27,969
Yeah, I feel like I already understand color/data loss at the extremes and try to avoid it (and like using the highlights view to spot it sometimes).... a histogram is a neat representation of it but not sure I'd ever really use it. Hmm.

It's the only thing you can use to accurately check exposure. Your LCD screen can't be trusted since the brightness probably varies a lot. The flashing highlights are fine, but it won't show if you blow a colour channel out.
 

Pikel

Active Member
May 25, 2003
186,476
PNW
i took a picture of my sister peeking outside the window. it's pretty bright on her face to the point where there really isn't much detail left...and then behind her is really dark....any advice on how to make her have detail while also lighting up the back a bit?
Fill light.
 

MSIGuy

om nom nom nom!
May 30, 2005
4,705
i took a picture of my sister peeking outside the window. it's pretty bright on her face to the point where there really isn't much detail left...and then behind her is really dark....any advice on how to make her have detail while also lighting up the back a bit?
You can also switch to spot metering. You need to tell the camera what area of the frame you want to expose to, if you don't it's going to just try and make an average exposure, and that's what you end up with.
 

MSIGuy

om nom nom nom!
May 30, 2005
4,705
[y]8tojMWjrD8w[/y]

[y]lpSi27u4azQ[/y]
Fucking no! They're both doing it wrong! :rofl:

You don't randomly blow into your sensor chamber, sometimes it'll work but most of the time you end up blowing more shit onto your sensor than you wanted to remove. Just a couple of blows, then you move onto another technique.

And the second one was close, but you don't lift the swab up and flip it over like that, when you do that you end up leaving streaks and shit on the edge of the AA filter...

I should get working on that EDU soon... :rofl:
 

dmora

Fucking no! They're both doing it wrong! :rofl:

You don't randomly blow into your sensor chamber, sometimes it'll work but most of the time you end up blowing more shit onto your sensor than you wanted to remove. Just a couple of blows, then you move onto another technique.

And the second one was close, but you don't lift the swab up and flip it over like that, when you do that you end up leaving streaks and shit on the edge of the AA filter...

I should get working on that EDU soon... :rofl:

go on?
 

MB300E87

Active Member
Jun 4, 2001
13,023
California
what do you guys do to keep your chops up? what do you practice on when there aren't events or jobs that you've booked where you need to be shooting?

i know the question isn't very specific but i don't have pets or kids so my access to "interesting" subjects to practice on is pretty limited.
 

Cicada

Abraham $LINK’in
OT Supporter
Sep 30, 2008
177,743
SoCal
should a light meter be aimed at the camera or at the light source?
depends. i aim at the camera if im getting an overall reading. if i want a reading of just one light, ill either retract the sphere and aim it at hte light i want a reading of, or shield it/turn off the other lights.

if i'm outdoors, i aim it at the camera in an attempt to get an "even" reading of both ambient and flash.
 

Chitown B

Active Member
Oct 13, 2008
26,944
chicago, il
is there a way to meter the background and still get enough light in the foreground, without a fill flash? Lots of times I'll want the sky and person in front of me exposed correctly but usually can only get one or the other.
 

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