[Recovered Thread: 78774]

[Ken Rogers]

I'm really starting to love my new FZ5. This shot was taken at 10pm from approximately 1/2 mile away. I set the ISO to 200, aperture wide open, and shutter speed at 1/2 second, although the camera recommended a longer exposure. Iwas fullyzoomed to 12x. Noise was removed afterwards with "Neat Image".

I'm happy with this shot but would like opinions and suggestions for improvement. A friend of my (who considers himself tech-savvy) told me that digital cameras can only simulate ISO, aperture and shutter speed. Surely that's not true! Can someone shed some light on this (no pun intended :G).

Ken

[Stump1000]

Nice picture man. I like it. Better let someone else answer your questions though. lol

[Corpsy]

Nice picture. You used a tripod, right?

On the ISO thing, I think your friend is basically accurate. Try this, take a properly exposed picture in manual mode at ISO 400. Then turn the ISO down to 80 and take the same picture again. Bring them both into Photoshop. Add a levels adjustment layer to the ISO 80 picture and correct the levels to brighten the picture. When I tried this, I found that both images turned out basically identical.

I don't know if ISO does something different on an DSLR camera. I have one at work and haven't tried that specific test, but I'd be a bit surprised if I could get the same results with a properly exposed ISO 1600 image on a very underexposed ISO 100 image. I'd have to use RAW to test it fairly though, a lot of that dark data would be thrown out when saving down to JPG.

[José A.]

Ken Rogers wrote:

A friend of my (who considers himself tech-savvy) told me that digital cameras can only simulate ISO, aperture and shutter speed. Surely that's not true! Can someone shed some light on this (no pun intended :G).

I'm no technical, but as far as I understand the camera does have a diaphragm (is that the English word?) and does regulate the shutter speed, so thosetwo are not simulated.

About ISO... well, let's just say for now that I'm no technical.:-x

[squirl033]

digital "ISO" is merely a convenient name we all recognize, applied to the process of electronically adjusting the sensitivity of the sensor to light. with film, the ISO (or ASA, for us old-timers) was determined by the chemicals in the film emulsion. with digital technology, we can "simulate" that by varying gain of the photodiodes in the sensor. more gain =more sensitivity, higher ISO. lower gain =less sensitivity, lower ISO. it's a very easy function electronically. yes, you can compensate for a darker or lighter image in PP, but that's a function ofincreasing or decreasingthe brightnessof the pixels in the image... not at all the same thing, though it has almost the same effect on the image when you view it.

i don't know if there's actually a mechanical iris in digital cameras... if there were, you'd probably here it working when you take a picture, though, and most digitals are silent unless you have tbe "beep" turned on, or (like me) you like the "click" sound effect Panasonic thoughtfully included for nostalgic purposes in the FZs. i don't know how you'd "simulate" a mechanical iris, though i'm sure someone more techie than i am could offer an explanation...

[Ken Rogers]

Yes, you can compensate for a darker or lighter image in PP, but that's a function ofincreasing or decreasingthe brightnessof the pixels in the image...

On occasion I've taken some very dark pictures, then dragged them into Photoshop and cranked up the gamma on them. Extra detail is revealed, but only to a point. I'm sure thatusing the correct ISO setting in the first place is sure to give better results. I just hope my camera isn't simply "faking it" by increasing the brightness of the pixels after the exposure process is complete, because this would be the same thingthat Photoshop "Levels" does for you.

As for the shutter, I've read that digitals simulate it perfectly by adjusting the sensor's "on" duration. I'd like to know about the aperture though. I am new, and haven't really had any need for depth of focus, but would like to know if an iris really exists.



PS: I did use a tripod for this. I also used the two-second delay feature, so I wouldn't shake the camera when I squeezed the button.

Ken

[Corpsy]

Here's an article that does a bit to explain how ISO works in digital cameras. Some cameras handle it differently. I suspect that cameras like my FZ30 use "bit shifting".http://www.cs.duke.edu/~parr/photogr...tml#isomeaning

[Ken Rogers]

Very interesting. Some of it goes over my head (i.e. "underexpose and push in raw conversion"?). With the shot I took above, there are areas that are blown out. I wish I'd used an even lower ISO, then brightened selectively afterwards in Photoshop (using "curves").

Thanks for the link. I'll read it twice.

Ken

[José A.]

squirl033 wrote:

i don't know if there's actually a mechanical iris in digital cameras... if there were, you'd probably here it working when you take a picture, though, and most digitals are silent unless you have tbe "beep" turned on, or (like me) you like the "click" sound effect Panasonic thoughtfully included for nostalgic purposes in the FZs.

My FZ10 does have one... if you're not sure, try making the same shot with different f-stop values and check the depth of field later.