AlanKlein

1 hour ago, glen_h said:

For comparison, the data sheet for Portra 400 is here:

https://imaging.kodakalaris.com/sites/default/files/files/resources/e4050_portra_400.pdf

 

The main part of the curve, well all three of them, is amazingly straight!

It covers about 3 log10 units on the exposure axis, and has not started to curve over at the top.

It might have another log10 unit left before it curves too much.

The 3 log10 units, gives about 10 stops, but maybe 12 or 14 if they kept the curve going.

Match up to the density units on the left, and the slope is about 0.5, usual for C41 films.

(That is also usual for C41 black and white films like XP2.)

For a scene that fits in the 6.5 stops of Ektachrome, the additional maybe 6 means that

you can overexpose 6 stops, and still be within the straight part of the curve!

 

The low 0.5 for the slope means that you have to be pretty close when printing.

Color negatives are always printed with an enlarging light meter. 

 

The slope of about 0.7 for more usual black and white films, means you can usually

get away with using test strips, and get close enough.  And maybe only 3 or 4 stops

of overexposure.

I found when I bracketed +1 and -1 stops, there is a color shift in the greens especially, even though all three shots can be adjusted for proper luminance exposure after scanning.  

I swear.  I'm not guilty.

The guy's face on the left is messed up.  So are the faces on the right.

Red Rock Canyon, Las Vegas

Straightening is good idea.  I'd also crop the black out off the bottom. 

7 hours ago, danac said:

I'm guessing that at least 90% of the better B/W landscape images I've made over the last forty-four years with an AE-1 or A-1 (fifty-four if you include my old Pentax Spotmatic SP) were made using the settings my meter gave me. Sure some of those could have been a bit better by exposing for the shadows et al.. But overexposing with this tiny format will most often make for a grainier image which I personally don't like. In the last few years I've made a lot of poor negatives by over doing the creative routine. From now on I will trust my meter for at least one image and play with exposures for a further one or two just for fun. I know that Ansel took a dim view of bracketing but I just ain't as clever as he was.

Ansel's dead.  Bracket away.  I do.  

41 minutes ago, Niels - NHSN said:

Blind Magazine have a pretty thought provoking article:

https://www.blind-magazine.com/en/stories/how-ai-imagery-is-shaking-photojournalism/

When hands are visible, they are the usual giveaway.

The author's photographic work with AI takes cloning and fabrication to a new level.  It creates fake photos to tell a story that is only in the mind of the creator.  From a storytelling angle, it's a new method. Not much different than a novelist.  From a journalistic point of view, it creates real problems that will need time to get sorted out.  "Did you Photoshop it?" will become a rather mild question once AI gets really going. 

21 hours ago, Dustin McAmera said:

I remember finding with dismay how much it would cost to get the standard (ISO 732) for the design of 120 and 127 film (I hoped I could either quote it or link to it in Camera-wiki), though I knew I'd been able to download older versions free. Then I remembered that was because I worked at a university before, and we had a subscription. I know the ISO must cost a lot to run, and a lot of their customers are commercial and should pay for the information: but it feels unjust as a little citizen, that standards cost so much: 'This is the law, and it'll cost you sixty bucks to know what it is'.

Most standards are created by private organizations not the government, hence the cost.  The laws usually refers to standards by name and number and don't necessarily describe all the details which can be very complicated.  This way, they don't have to change the law every time the standard is upgraded.  If the government creates the standard, then it will be described in the law at no cost to the citizens. 

10 hours ago, weasel_bar said:

Does anyone know how ISO is defined for slide film? For negative film, ISO is defined by the speed point, where density is 0.1 above baseline. According to Wikipedia, for slide film, ISO is "determined from the middle rather than the threshold of the curve." I tried looking up the definition on ISO website, but it costs 61 swiss francs to find out. Does anyone know what is the technical definition of ISO for reversal film?

 

What does the differing calculations mean to the average photographer?  For example, box speed ISO 100 on reversal vs positive color film means what?

On 4/20/2023 at 2:11 PM, movingfinger said:

I made a self-published book on blurb and I was very pleased with the results. I used lightroom to create the book and just shipped the result to blurb. I did go with the highest quality paper. You can see the resulting book, which has both color and BW images, on the blurb website as I make the entire thing preview-able. On my screen the images look like they do in the finished paper publication. You can find it here and see for yourself, click on 'preview'. 

Very nice.   Labor of love.   I did my first Blurb soft cover of my grandson's first birthday party.  The first came out too dark but they re-did it after I lightened it up in Lightroom first. 

I was just thinking.  Why would Sony, a camera manufacturer, ever create a contest for AI when cameras don't have to be used?

Dead Horse Point, Utah

I don't think there's any issue using AI for art just as one would create an oil painting.  The problem is when AI is used to present a documentary photograph that isn't authentic in its representation. At least with Photoshop, you started with a photo or photos.  With AI, you don't even need a camera or leave your computer desk. 

How does one create an AI photo?

John and Mike.  I stand corrected.  You both make sense. 

I have a question. Regardless of white, black or 18% gray, the histogram should show the data in the middle? What if it's slightly off middle?  Is that calibration or something else? 

10 hours ago, mike_halliwell said:

If i remember my metering, any monotone background subject to Auto, be it black, grey or white, should register as a centered mole-hill on the histogram.....

that's how they're calibrated.

9 hours ago, John Seaman said:

Not necessarily. As long as it's a neutral surface with no colour cast.

All the camera sees is an illuminated area, it doesn't "know" what the reflectivity is, or how brightly it is lit. No matter what automatic exposure mode or metering pattern is used, the meter should set the camera to place the histogram centrally.

I was surprised to find my D700 overexposing, it's not impossible for metering to misbehave.

Metering is based on 18% gray scale.  If you use a white card, shouldn't the histogram data show on the far right?  If using a black card, shouldn't it be on the far left? Shouldn;t the 18% gray be in the middle?

5 hours ago, John Seaman said:

When I first had my D700, it consistently over exposed.  There's a custom setting called Fine Tune Optimum Exposure, which lets you change the settings for the different exposure modes, spot, centre weighted and matrix. By setting them to minus one, the exposure is fine. To test it, just take a picture of a plain grey surface and check that the spike on the histogram is centred. I don't know if this custom setting is available on the D7000, it certainly is on my D7100.

I suppose you mean an 18% gray card?

That's an interesting point though, John.  I have to check my camera to see if it keeps the histogram in the center when on shutter or aperture priority or whether it's offset.  If it isn't, could the metering be off?  Factory set? I don't believe my Olympus micro 4/3 E-PL1 has Fine Tune Optimum Exposure feature or its equivalent.

11 hours ago, paddler4 said:

As someone who does drone photography, I am pleased that some parks ban them. Many people go to parks for peace and quiet, not to hear they high-pitched whine of drones. However, still photography in a parking garage is an entirely different matter, as it doesn't interfere with what other users do unless you take photos of people or their personal possessions.

But the OP was flying a drone from the parking lot building.

That's why I asked is that feasible to create images on its own?