That is nearly as big as my 400mm f4 lens, I have to put a converter on it to get to that sort of focal length so I would borrow the daughters
1800 mm f8 as its got better colour correction being a mirror lens design.
It weights in at 12 kg IIRC.
Not the sort of thing you want to lug about.
OTH she has a Sony with a 1200mm zoom which is easy to carry about. Its far better for casual photography as you have far more chance of getting the picture if you are moving about.
You could use a single line scan camera, they work quite well.
The camera maker can't actually put it in the best place as its different for each lens.
It is a telescope, it probably isn't a very good one as you can cut quality right down for photographic use as the sensors and film are pretty poor when compared to the eye.
A telescope will probably have optics surfaced to 1/8 wavelength while camera lenses are probably >100 times that.
Ah, OK. My mistake for mentioning what's turned out to be a total red herring :-(
It seems that manufacturers positioning the tripod point roughly where the sensor/film is coincidence and that rotating about that point doesn't make much sense for panoramas or for movie work where you don't want perspective changes as the camera pans.
Try and think about what it says and stop talking bollocks.
the DoFocus is the complement of DoField one at one side of the lens and the other at the other side of the lens. Unless you are designing lenses they have exactly the same effect and on a camera you change one and the other matches it.
i posted that link so as to help you understand but you obviously can't be bothered.
I know enough about teaching to know that teaching the stuff correctly is a good starting point and being so pig ignorant that you won't listen to someone who knows telling you what is wrong is not a good attitude for a teacher.
There are always new things to learn. At least you want to learn unlike some.
Its quite difficult to grasp the concept without proper explanations and a few drawings. I wouldn't expect the average photographer to even know about it. I would expect cine camera operators to know.
I hate to think what the next generation of photographers "know".
Dennis, as far as you are aware, is Whisky Dave correct to call the "London Underground" circle-and-bar symbol on most SLRs the "depth of focus" mark? I think the symbol marks the position of the focal plane and that the DoFocus is, as the explanation above says, a range of distances either side of the lens's focus point; when the lens's focus point is the same as the focal plane, the image will be in focus on the film/sensor.
Or is "depth of focus" ever used colloquially (and incorrectly) as a synonym for "focal plane"?
are yuo saying more accurate than a digital camera, so doesd this mean one of those film cameras is BETTER than a digital camera ? So why were you asking me whether or not film is better than digital for anything ?
irrelivant and not even true.
So it has no use then is that your claim.
No the aim is to teach photography.
Yes they are I told you that, but both have the abbrevaition of DoF.
Rubbish the deapth of focus indicator doesn;t need top move depending on teh lens used. The lens is designed so that when focused at infinity the image is in focus at teh film plane for visable light.
Flashguns have guide numbers which represent the light output at a particular distance, changing this distance means less or more intense light which means to cointoll this you need to adjust the aperature in most cases.
yes I know and until I know what 'compact' camera witout an interchaable or additional lens options, I can imagine why they'd bother or explain it. I can expalin why Lieca brought out a camera with snake skin.
I don't care and I doubt many people care where the tripod mount it. NOTICE I said people NOT photographers.
1800mm at f8 which lens is that. I want two so I can make a pair of binoculars for 3D photography ;)
wimp ! :-)
I though the problem with mirrors is that you can't stop down to increase deapth or field, Tjhey are fixed aperature) which is why the vast majority of pros use standard refractive lenses rather than mirrors.
are in satisfactory sharp focus, the limits being the establishment of a c ircle of confusion of greatest acceptable size.
sion of the film) can be moved backward and forward with respect to the cam era lens such as defined under the depth of field and circle of confusion. This term is often confused with depth of field and vice versa.
d in; it is what is in acceptable focus in front of the lens. Depth of Focu s is what only a technician is interested in; it is what is in focus behind the rear lens element which the film or image sensor "sees."
Try talking to a photographer and NOT someone that think photgraphy started with digital camera.
I think what WD is not saying is this: you need to know the exact distance from the flash to the subject to use the guide number to calculate the correct aperture. Rather than measuring from flash unit to subject, he's measuring from focal plane mark to subject.
I've rarely used guide numbers because my flash units have either been completely automatic, metering the reflected light through the lens, or else have had a sensor on the flash unit which does the same job, in which case you need to set the aperture manually according to an ISO versus aperture scale.
The manual flash units I had used a rotating scale: you preset the ISO and then found the distance and read off the corresponding aperture which does the guide number calculation for you (in the same way that a slide rule performs multiplication or division for you).
I tend to read the distance off the lens's focus scale rather than getting a tape measure out, though at close distances (maybe less than a couple of feet) accurate measurement may be a bit more important.
I'd have to google how exactly you use a GN. From memory it's something like: every flash unit quotes a series of GNs for different ISOs and you divide the GN by the distance to give the aperture (two GN values are quoted, for feet and metres). That's the principle, even if I've forgotten the fine details.
This is called *sharing* knowledge as opposed to trying to be superior and saying "if you're not clever enough to know, I'm not going to tell you" which is childish and unhelpful - I worked for a guy who thought that this was a way of motivating people, whereas it does just the opposite for me.
Mirror lenses also have very characteristic bokeh. But I won't make disparaging comments if people have to google to find out what bokeh is and what is characteristic about that of a mirror lens!
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