Alley in Pisa, Italy

by Lars Kotthoff

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F/22 suggests to me that the photographer first took some pictures with nearby objects in the foreground and then forgot (or didn't bother) to increase the aperture for this particular shot. The ISO setting of 640 is then quite appropriate, you can go lower with a longer exposue time, but as the other answerers point out that can cause problems if the clouds ...


1) Be simple. (s)he forgot to switch to the lower ISO. ). For example, (s)he wanted to catch a bird before. 2) But I heard one story from an older photographer (?) about the long exposure (sensor reheating during the long exposure): sometimes it's better using short high ISO shot vs. long exposure shot to avoid noise. The best solution to make two shorts ...


A very narrow aperture such as f22, which allows for an almost infinite Depth of Field, lets in very little light. ISO 640 may have been required to ensure the shutter speed stayed at a reasonable level, if the photographer didn't want to risk camera shake from wind or cloud blur.


Perhaps the photographer believes that ISO 640 can be LESS noisy than ISO 100. I'm not necessarily supporting that viewpoint, just stating that there is one.


The photographer chose a slightly higher ISO to compensate for using f/22 aperture (small opening = less light). You may ask, so why not make the shutter speed longer? The shutter speed was set to 1/6th of a second, rather than say 10 seconds, so that the image is nice and sharp, it may have been windy and might have shaken the tripod even just a little bit. ...


One (remote) possibility, based on a different camera... My Fujifilm X-Pro1 has a "dynamic range" setting that lets me choose between 100%, 200%, and 400%. Higher settings are supposed to extract more shadow and highlight detail (almost like a simulated HDR) in the out of camera JPEgs. BUT the 200 and 400 settings are only available at higher than minimum ...


I can't buy the clouds moving being an issue here. However, I can think of one reason that would be invisible: There are mobile objects near the photographer that sometimes get in the frame. He shot quickly to avoid them. He might have shot several, this is just the one that actually worked. I do think it's more likely an oops, though.


Disclaimer: this answer is highly dependent on equipment, firmware, etc. and may actually be conjecture. Another possibility is that the digital camera is not optimized for the lowest ISO values. If you look at the internals of a camera some sensors do not support "50 ISO" and instead the camera firmware shoots at about 160 - 200 and pulls the exposure ...


It could have been very windy. =0)


The only technical reason I can see in this particular case is that there might be some traffic on that road that you don't want in your shot. Thus the faster shutter speed was required to catch it between vehicles. Not that I think this was actually the reason, since the timeframe for ISO 100 is still pretty short.


I can't think of any technical reason for this to be the case. Even assuming that he used the lens at 105mm, if he was more than 387 ft from the closest object in the frame, he could have focused at 750 feet and had everything in focus even at f/5.6, so f/22 was completely unnecessary unless intending to get the shutter speed longer. A faster shutter speed ...


The mountain and the valley obviously are static -- even more from that distance. The clouds, however, move. If you chose a low ISO value, e.g., in the range of 50 to 100, the exposure time might be enough to get washy/faded/blurred clouds. If I calculated it correctly, an ISO value of 100 with the other settings (exluding shutter speed) staying the same ...


They simply mean that when using a higher ISO, you can use a higher shutter speed, smaller aperture, or both. There is no such thing as "reduced exposure parameters." It seems like you don't have a good grasp of exposure. There's a good primer at


The optimum ISO is whatever ISO you need for the exposure you want. ISO adjustments on a digital camera simply boost the sensitivity of the sensor, either causing some forms of noise to be amplified as well or causing a reduction in dynamic range. If you were to under-expose an image and gain it up later, you still get the same noise amplification, but you ...


The manual probably tells you what the "base" ISO setting is. That will be the one with the least noise. On my camera, for example, that's ISO 200. However, the best way to learn what the tradeoffs are with various ISO settings for your camera is to take your own test shots. The base ISO will have the lowest noise, but that alone doesn't tell you enough ...


Generally speaking if you want the least amount of noise you typically want the base ISO which is likely around 160 on your camera. This is worth a debate(already done here) because underexposing an image can introduce noise so if you can properly expose at ISO 160 that will give you the most noise free image. If you want the "optimum" ISO it depends. ...

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