All Forum Comments
Comment by petrochemist posted on Microsoft ICE Panoramic Software at 03/12/2013 - 13:48
It's very simple.
The change in relative sizes of objects is due PURELY to their relative distances. Try holding your hand close to your face then at arms reach & you'll see it's size relative to the background looks different.
The problem arrises because diferent focal lengths encourage a change in view point, which changes the relative distances of the objects.
The relative sizes of wide angle & telephoto images with the same relative distances (same spot) are identical. You can check this as recompended earlier up thread, or by stitching together telephoto images to civer the same angle of view, or even just by measuring relative sizes with a ruler.
Things differ if you use distorting lenses (fish-eye lenses) or at very short distances where it's difficult to keep the relative distances the same - which part of the lens/camera combination you measure to becomes significant.
The change in relative sizes of objects is due PURELY to their relative distances. Try holding your hand close to your face then at arms reach & you'll see it's size relative to the background looks different.
The problem arrises because diferent focal lengths encourage a change in view point, which changes the relative distances of the objects.
The relative sizes of wide angle & telephoto images with the same relative distances (same spot) are identical. You can check this as recompended earlier up thread, or by stitching together telephoto images to civer the same angle of view, or even just by measuring relative sizes with a ruler.
Things differ if you use distorting lenses (fish-eye lenses) or at very short distances where it's difficult to keep the relative distances the same - which part of the lens/camera combination you measure to becomes significant.
Comment by petrochemist posted on Something to ponder! at 26/11/2013 - 12:19
johnha wrote:
It's not difficult to get average results, beyond that takes a lot of effort/experience/gift etc...
I can't point you in the direction of a website, I learned from several books on 35mm photography (probably by Michael Langford), but the basics are fairly easy (it gets more complicated but this is enough to get started):
Your film speed (ISO) is fixed by the film you load and determines the amount of light you need for a 'correct' exposure. The ambient light level determines your shutter speed/aperture combination required to achieve this. Longer shutter speeds (lower numbers) let in more light and vice versa. Wider apertures (lower numbers) also let in more light and vice versa. For a given light level and ISO, a wider aperture means a shorter shutter speed and vice versa. For each 'step' in shutter speed (called a stop) there is a corresponding step in aperture (in the other direction). There is usually some overlap in the shutter speed/aperture combination to allow flexible choice in the following:
Shorter shutter speeds freeze movement, longer ones blur it. Wider apertures produce less (shallower) depth of field, smaller apertures produce more (deeper) depth of field. Shorter focal lengths create more DoF for a given aperture, longer ones create shallower DoF for the same aperture.
When you get the LX put it into manual mode (shutter speed dial not in 'automatic'). As you change shutter speed or aperture, you should see the red LED in the finder move up or down corresponding to the recommended speed for the given ISO, ambient light level and aperture. When the indicator of your set speed lines up with the LED, that means you're set at the recommended exposure. Take note how this works (easier to see for yourself than trying to explain it) pointing at different light levels.
Slide (transparency/E6) film shows up errors immediately (print film is 'corrected' in the printing process) and noting your settings when shooting will help you work out what (if anything) is going wrong.
Hope this helps, there must be useful stuff on the web too.
John.
John summary here is very good, but there's a couple of points that could be added:It's not difficult to get average results, beyond that takes a lot of effort/experience/gift etc...
I can't point you in the direction of a website, I learned from several books on 35mm photography (probably by Michael Langford), but the basics are fairly easy (it gets more complicated but this is enough to get started):
Your film speed (ISO) is fixed by the film you load and determines the amount of light you need for a 'correct' exposure. The ambient light level determines your shutter speed/aperture combination required to achieve this. Longer shutter speeds (lower numbers) let in more light and vice versa. Wider apertures (lower numbers) also let in more light and vice versa. For a given light level and ISO, a wider aperture means a shorter shutter speed and vice versa. For each 'step' in shutter speed (called a stop) there is a corresponding step in aperture (in the other direction). There is usually some overlap in the shutter speed/aperture combination to allow flexible choice in the following:
Shorter shutter speeds freeze movement, longer ones blur it. Wider apertures produce less (shallower) depth of field, smaller apertures produce more (deeper) depth of field. Shorter focal lengths create more DoF for a given aperture, longer ones create shallower DoF for the same aperture.
When you get the LX put it into manual mode (shutter speed dial not in 'automatic'). As you change shutter speed or aperture, you should see the red LED in the finder move up or down corresponding to the recommended speed for the given ISO, ambient light level and aperture. When the indicator of your set speed lines up with the LED, that means you're set at the recommended exposure. Take note how this works (easier to see for yourself than trying to explain it) pointing at different light levels.
Slide (transparency/E6) film shows up errors immediately (print film is 'corrected' in the printing process) and noting your settings when shooting will help you work out what (if anything) is going wrong.
Hope this helps, there must be useful stuff on the web too.
John.
The Field of View , is bigger with shorter focal lengths.
For 35mm film a 50mm lenses sees about the same as your eyes, a 24mm wide angle will give about twice the angle of view and a 200mm telephoto will look like its 4 times larger.
In shutter speeds each 'stop' is a two fold difference in time, while with apertures it's a two fold differnce in the area of the opening. With a constant light source half the time through twice the area is the same number of photons to expose the film.
ISO is ameasure of how sensitive the film/sensor is to photons double the ISO & you only need half as many photons.
(Photons are effectivly individual bits of light, there's absolutely no need to understand them which is just as well!)
Comment by petrochemist posted on I know nothing about photography but I've bought an LX. Help! at 22/11/2013 - 15:49
Although I'm usually very anti flare, I prefer the first with the startburst to the second.
In fact I prefer the sky & sea areas from the first and feel the silhouetted land/people bit the second is marginally better.
I have to add I think the composition from the phone has advantages over both due to added foreground interest...
So all three are winners
In fact I prefer the sky & sea areas from the first and feel the silhouetted land/people bit the second is marginally better.
I have to add I think the composition from the phone has advantages over both due to added foreground interest...
So all three are winners
Comment by petrochemist posted on Midnight Sun - the difference aperture can make to an image at 22/11/2013 - 14:58
Darkmunk wrote:
Ha ha, ace!
I'd say a good proportion were deliberate.
+1Ha ha, ace!
I'd say a good proportion were deliberate.
Some really great images, but 5, 11 & 12 are the only ones that look like panoramas and no 11 was certainly planed.
The bath scene definitely wasn't from an attempt at panoramic stitching, I suspect it needed 4-5 carefully planed shots that were manually merged in Photoshop.
Despite this they're well worth a look!
Comment by petrochemist posted on Found these epic pano failures online... at 19/11/2013 - 18:10
As the others have said the second is incredibly good.
It's not often you get to see under a single seater on the track, and the clouds of cement dust behind help pick it out too!
It's not often you get to see under a single seater on the track, and the clouds of cement dust behind help pick it out too!
Comment by petrochemist posted on Motorsport: Brands Hatch Formula Vee Festival at 12/11/2013 - 16:03
andrewk wrote:
Andrew
The spacing looks to me as if it matches the blinds fairly closely. I'd certainly expect it to be lens flare from the window.JAK wrote:
Or it could be a reflection within the lens of the light from the window.
If it is just on this photo, that would be my guess too.Or it could be a reflection within the lens of the light from the window.
Andrew
FWIW I could see it straight away on your grandmother, but can't spot it at all on either of the boys.
Comment by petrochemist posted on Under chin Ghost? at 12/11/2013 - 15:56
Offertonhatter wrote:
In that case John, play fleabay at their own game. Non-AF lenses are vintage, cheaper to list. Any Pentax user worth their salt will know one lens from another and search accordingly.
Surely the listing fee is the same in each, it just cost more to use more than one.In that case John, play fleabay at their own game. Non-AF lenses are vintage, cheaper to list. Any Pentax user worth their salt will know one lens from another and search accordingly.
I suspect many photographers would look under 'usable' but not 'vintage/collectable' whilst collectors would probably have searches to look in both.
Comment by petrochemist posted on Where Do We Draw The Line? at 11/11/2013 - 09:30
Given m42 lenses are regularly used by many types of dslr (pentax, canon, sony...) I'd very much class them as usable too.
IMO lenses that need modification or custom adapters to be used with ANY modern camera would fit in the collectable class. I have a couple from prewar folding cameras, that have been jury rigged via bellows, still usable after a bit of work but more vintage/collectable. All of my Large format lenses would probably fit in that class too.
Especially rare m42/K mount lenses such as the 1000mm reflex could be listed in either (& probably should be in both). The early M39 screw mounts and the MEF's lenses are the only pentax lenses I'd be unsure about classing as usable.
Until about 5 years ago FD lenses were pretty much useless with any modern camera, so would have been considered collectable (or junk). Now there are many adapters available for them to be used with mirrorless cameras, so I'd say they were usable again.
IMO lenses that need modification or custom adapters to be used with ANY modern camera would fit in the collectable class. I have a couple from prewar folding cameras, that have been jury rigged via bellows, still usable after a bit of work but more vintage/collectable. All of my Large format lenses would probably fit in that class too.
Especially rare m42/K mount lenses such as the 1000mm reflex could be listed in either (& probably should be in both). The early M39 screw mounts and the MEF's lenses are the only pentax lenses I'd be unsure about classing as usable.
Until about 5 years ago FD lenses were pretty much useless with any modern camera, so would have been considered collectable (or junk). Now there are many adapters available for them to be used with mirrorless cameras, so I'd say they were usable again.
Comment by petrochemist posted on Where Do We Draw The Line? at 09/11/2013 - 14:43
Hope the 'DA wide zoom', comes at a reasonable price. It fills a gap in my range that I can't currently afford.
The 'DA tele zoom' seems to cover ~120-380mm so perhaps the long awaited long lenses might be on the way.
Shame about the TC, but it wouldn't have been for me anyway.
The 'DA tele zoom' seems to cover ~120-380mm so perhaps the long awaited long lenses might be on the way.
Shame about the TC, but it wouldn't have been for me anyway.
Comment by petrochemist posted on Updated Roadmap at 07/11/2013 - 21:35
It copes remarkably well with poor alignments. I've had a run of 7 or more handheld telephoto shots from a moving ship printed as a banner (over 10' long) and you have to look hard to spot the joins. It did fail to match on another similar run, but I suspect it was due to a rather plain patch of coastline.