Digital
Dilemmas
Hugh McLean-bsme, thb.
Camera resolution dilemma
There is an inverse relationship of resolution to film speed that is all but etched in stone with most of us. The slower the film speed is - the higher the resolution is, and visa versa - the faster the film speed is, the lower the resolution is. If you wanted fine detail in your final image, you selected a film with a slower film speed - which supposedly - produced higher quality images. Emulsion thickness and film speed also had a direct relationship. The thicker the emulsion, the faster the film speed and the thinner the emulsion, the slower the film speed. My first attempt to get sharp crisp prints involved using a very very slow film (Adox KB-14) developed with a one shot developer (Neofin Blue). It didn’t take long for me to realize that there are huge trade-offs that are sacrificed to achieve small grain size, which can easily defeat the initial intent. When the first ISO 400 color film came out, unlike the current 400 film, it was admittedly quite grainy. A 16x20 printed from a medium format negative looked like it was printed on coarse sandpaper. I used it because a faster shutter speed minimized camera shake and subject movement which were more significant to the quality image I was looking for, than the slower speed and finer grain films.
Along comes the digital camera with ISO speeds that are ‘switchable’ with a flick of the dial, and along with it a dilemma as to which speed is the correct one to use. I wrote the preceding paragraph pertaining to film because most photographers are more familiar with the various ramifications of ‘film’ speed than they are with a digital ISO speed. My logical instincts assume that the digital ISO is relatively equivalent to the film ISO. That assumption carries with it the preconceived notion that there is an inverse relationship between resolution and ISO numbers. I bet if I took a survey, most would be under the impression that the ISO on the digital camera functions the same way as film ISO. Do you get higher resolution with a lower ISO number on your digital camera? What does the ISO number on the digital camera really mean? What about file size? Do I get a higher resolution with a larger file size? What about the image size? Do I get higher resolution with a larger image size? The answers to these questions are not as intuitive as you might first imagine. The tests that I have made indicate results that the ISO number, for example, only seems to matter significantly when ‘artifacts’ or ‘noise’ appears, and the they become more apparent when the lens is pushed to its limits. The lens quality seems to have more bearing on the final image quality than does the ISO. One of my long lenses will produce acceptable results at ISO 1600, while another similar lens will not - even though the unacceptable lens worked fine with film at ISO 3200. The resolution tests that I have made so far, seem to indicate that the ISO speed - at least with my current camera (Fuji S2) does not significantly affect the resolution up to about ISO 800. I suspect that most of the complaints of the S1 not having an ISO 100 were based on the preconceived and erroneous notion that lower ISO = higher resolution. The one situation where the lower ISO is needed, is in bright sunlight when a fill flash is required to lighten shadows under the eyes. Since the maximum sync speed is 1/125, a lower ISO is helpful to keep the f-stop from getting out of range of both the lens and the flash unit.
I am always amazed when I read articles repeating the mantra of file size required to print an 8x10 and equating that to camera ‘resolution’, when in reality, the camera settings that are referred to as ‘resolution’ are actually degrees of ‘compression’. There is a huge difference.
New math dilemma
When does 356 - 354 = 3; 356 - 349 = 9; 356 - 344 = 15; etc.? Freudian series calculus? The countdown exposure number on the window of the S2 indicates the number of exposures that the storage device can contain after the last exposure has been stored. After the jpg crunching apparatus finishes extracting bits from the last exposure, there are bits left over that sometimes make enough space for an extra exposure, and the extra number is added to the exposure counter - or so it seems. Hence there are (2) number 354, (2) number 349, (2) number 344 - etc. /*hm4/*
Comments and kvetches to:
misterdigital@comcast.net