joel_covey

<p>I agree that a digital sensor is linear and it has not-- and never will have--anything like the shoulder in a D&H curve. So with digital when you blow highlights they are gone forever.<br>

But when I'm talking dynamic range I mean working within the linear part of the D&H curve. That has a useful dynamic range of 7 stops (zones 2 thru 8) with any film I know about.<br>

A typical high end DSLR can collect over 40,000 photo electrons (p-) per pixel before saturation and has a noise floor (camera noise) around 10 p-. To make the calculations simple in my theoretical landscape photo the pixels of the bright white clouds in the sunny sky have 40000 p-. Then the dominate photon shot noise is 200 p- (sq root of the # of p-). That gives a signal to noise of 200.<br>

The pixels of cave with the rattlesnake near the bottom have only 100 p- (12 stops down from the clouds). There the camera and shot noise are equal, (10 p-) and since the two noises are incoherent and just as likely to cancel as add the total noise is 14 p-. So with a S/N of 7 our theoredical photographer will see the rattlesnake and set up his tripod well away from the cave.<br>

Toss in the latest advances of wavelet noise reduction and the digital dynamic range is even greater. So you can see why the newest DSLR now have in camera ISO settings of 25000.<br>

As an available light candid photographer I've willing sacrificed high recovery for low light performance. While I still have a few rolls of film in the frig and own a Nikon F3 I haven't shot a frame of film in years.</p>

<p> "There is still some work to do with increasing the dynamic range of a digital sensor but as far as getting more pixels is concerned - I think only a larger sensor will do it."<br>

To go OT a bit I keep seeing some version of the "film has a greater dynamic range than digital" claim in postings. Since from what I've read in the scientific literature and from my own experiments the DR of a digital sensor in a moderately low noise camera is now 11 to 12 stops. So if there is a better film out there where can I buy a couple rolls?</p>

<p>For the record and to keep the thread going I have the Promaster Spectrum 7 version of the same lens with a Nikon Mount. An excellent lens at an excellent price-under $30 with shipping</p>

<p>To quote somebody "Art was invented in the early 18th century by an Italian junk dealer when he discovered he could charge English m'Lords on a Grand Tour three time a much for his soot covered old pictures by calling them 'oggetto d'arte da mastets vecchio'-(art objects by old masters).<br>

Art is done by artists when they are in an artistic mood. Craft is done by craftsmen when they land an order. By this definition Jackson Pollock is an artist and Raphael is a craftman.</p>

<p>I bought a fiber optic lighting system for work a large number of years ago. It consisted of two flexible light pipes about an inch in diameter. two slip-on lenses and a halogen lamp in a case with a fan. Don't remember exactly what I paid but it was several week of my exorbitant salary. If we didn't need a source of cold light for a contract my boss would have never approved it.<br>

The big cost was the flexible light pipes. At one time you could buy short cheapie fibers that could be DIY in hobby shops in England but I could not find a supplier on this side of the Atlantic.<br>

On thinking more about it, I'd forget the worklight--too hot--and use an LED flashlight mounted to an adjustable stand. They color balance and would fit in close to the lens and sample</p>

<p>Old lenses with their chromatic aberrations and the DSLR= the 400X zoom button. The aberrations only became a problem when snap shooters could see them,</p>

<p>Nothing wrong with a fiber optic lighting setup except the big $.<br />I'm using an off camera flash with power control and a radio trigger. Works well and is useful for much more than macro photography. Sticking a smallish high intensity lamp by your wood sample works too. I've used a 150 watt work light from an autoparts store when I'm shooting 2 or 3 times lifesize. Just move it back and forth on the bench to set the illumination</p>

<p>At 200mm using a +4 diopter you are down to 1.4 times lifesize. Won't be nearly as sharp as a macro taken with a good macro lens but closeup lenses were the way I started.<br>

Another cheap way to macros--especially if you have an unused manual lens in a drawer--is to use e-bay extension tubes and, if needed, a reversing adapter (about $20). <br>

This is what I did with that type of setup <a href="

<p>Any way to delete a duplicated message in this forum?</p>

<p>At 200mm using a +4 diopter you are down to 1.4 times lifesize. Won't be nearly as sharp as a macro taken with a good macro lens but closeup lens were the way I started.<br />Another cheap way to macros--especially if you have an unused manual lens in a drawer--is to use e-bay extension tubes and, if needed, a reversing adapter (about $20). <br />This is what I did with that type of setup <a href="

<p><a href="http://francescobonomi.blip.tv/file/866674/">http://francescobonomi.blip.tv/file/866674/</a></p>

<p>He used CHDK. Google that and you will find the list of camera that can use CHDK</p>

<p>Auto focus is easy, sometimes fast and often overrated. One of the reasons I own a collection of manual focus lenses.<br>

I assume you are doing portraits and shooting wide open and from a distance of 10 ft. At f1.8 and 10ft your critical Dof is about 2 in. At f4 it increases to about 9 in--right for most portrait shots. And your image quality will go up. A new lens-I would return it. But with an old used lens, I would work around its limitations</p>

<p>Loose screws most likely.<br>

You will need the smallest JIS (Japanese Industrial Standard) screwdriver. You can buy them online. DON"T use a philip head!! They will mess up the head and cause you much grief<br>

In the lens I fixed, I unscrew the ring with the engraving and slid it up toward the top of the lens. The three screws holding the mount were underneath. I pushed everything tight and tightened the screws.<br>

Hope this helps</p>

 

<p>Check out CHDK for high end Canon non_DSLR cameras.<br />The DOF calculator may not be the script I use the most on my S3IS but it works well. A hobbiest wrote the code in his/her spare time. Not difficult to impliment at all.<br />And if you don't want to see it, one click in the config menu sends it away to forget-about-it land.</p>

<p>What does the iris do besides setting exposure? Aberration control. A big, big part of lens design. If the designer could have come up with a faster lens, you better believe the iris would have been bigger.</p>

<p>Noise. Every image has it and if you look hard enough you'll find it. 99.9 % of your viewers won't look that hard and if a few do they won't care. I've exhibited images with much worse noise<br>

The problem I see in your out of focus background--bokeh if you insist--is the blue squarish blob-a trash container maybe. It's too regular and jumps out of the rest of the background. Clone it out with your image editor and you will have a better image</p>

<p>Expectations--buy a new camera and all noise goes away<br>

Don't happen. The vast majority of the noise in any image is from the light not the camera. Photon shot noise, statistically dependent and caused by the random emission of photons that make the photo electrons that make the image. Fancy way of saying more light , less noise. <br>

But worth keeping in the back of your mind since the same laws of physics say to half the photon noise you need to make the pixels four times larger. Which you don't do when you move to a full frame camera.<br>

Pros end up with better pics in part by using faster full frame lens but mostly by using better techniques. Since the noise in the ref's shirt bothers the OP, he should mask it and and then clean it up using a decent wavelet noise reduction package. Wavelet noise reduction loves large areas of black and white with no detail.<br>

My two pennies.</p>

<p>Both the free RAW converters are standalone programs so you wouldn't have to download the full version of GIMP</p>

<p>I may get booed off this forum, but for a 16 year old I'd buy a moderately high end P&S with a movie mode and and all the other things that a teenage loves. A camera she will carry around in the book bag and use. If she is like most teenagers I know a DSLR will spend most of its life in her room<br>

And--I hang my head in shame--if the girl has a technical bend I'd buy a Canon. That way she can down load the free CHDK firmware extension and be introduced to joys of RAW processing and other interesting things that the Canon folks (and Nikon folks) forgot to implement in their firmware.</p>

<p><a href="http://en.wikipedia.org/wiki/Depth_of_field">http://en.wikipedia.org/wiki/Depth_of_field</a><br>

t'ain't a MYTH t's OPTIC<br>

see all them there "f"s<br>

that's where you put the focal length to make them there DOF numbers come out right</p>

<p>Raw conversion software normally looks at the header--a small block of information before the RAW data-- to decide if it is looking at a valid RAW file. While it's not impossible for the camera's firmware to become corrupted it's highly unlikely. So I'd focus on the memory cards which can have problems<br>

Do these experiments.<br>

Take a couple test shots using all your memory cards and see if your software recognizes any of the RAW files. If it does with some cards you know which ones are corrupt. Format these card and try again.<br>

If your camera can process RAW files with with different settings check to see if changing them makes a difference. Start by resetting the camera to its default mode.<br>

Try non photoshop converters. The GIMP versions--UFRAW and RAWTherapee-- are free downloads and more flexible about what they recognize than the Photoshop versions.<br>

Then come back and tell us what you learned.</p>

<p> </p>

<p>With long exposures you are dealing with thermal noise--the noise caused by electrons popping into a pixel randomly due to heat not light. It is linear with exposure--not a problem with exposures under a second or so but becoming more and more of a problem as your exposure becomes longer. That's why it makes sense to stack a series of short image like astrophotographers do rather than taking one long one.<br>

Thermal noise also doubles with every 6 degree C rise in temperature. So the cooler the sensor the lower the noise--the reason some serious astrophographers use cameras with Peltier coolers. Hot summer nights aren't the best time to take star trails.<br>

The sensors don't heat up--they don't use that much current. The big heat sources in your typical camera are the LCD and the internal batteries. Turn off the LCD--an easy fix. And if you have an extra working car battery lying around screw into the lead part of the middle cell for a quick and dirty 6 volt supply.</p>

<p>I've done something similar using GIMP, the free open source editor. Unfortunately I just bought a new laptop and don't have GIMP installed yet, but as I remember it was straight forward. Enter the number of pixels you want and then move the crop box to where you want it</p>

<p>Looks like something is out of alignment in the lens assembly. The edges of the shadow would be sharp if it was the sensor. And once a pixel is bad it stays bad</p>

<p>Hate to say it in a Nikon forum but buy a Canon and add the free CHDK (google it) firmware extension. It adds all the stuff the Canon Marketing folks left out of the camera-starting with RAW--plus some features they never thought of. By now there are 30-40 cameras supported (check the list) so you should find what you need.</p>

<p>I noticed a speed difference recently when I filled up my type III card and had to use a slower speed card out of another camera. If you are into sports and other burst mode photos type III cards are worth the extra money.</p>