Spring 2012

Spring 2012
by ani

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37

Split-prism focusing depends on your using fairly fast lenses. When the normal "kit" lens was a 50/1.8 (or 50/1.7, or something similar) that worked well. With slower lenses, one side or the other (or both) will be "blacked out" nearly all the time, and it provides no help in focusing. A typical kit lens nowadays is a zoom with a maximum aperture of ...


17

here's a couple of potential disadvantages: blackout: Split-prism focusing screens tend to turn black in the center with slower lenses (usually f/5.6 or slower, depends on the screen). Unless you're using a slow lens, or setting the aperture manually, this probably won't be a major problem. effects on metering: Focusing screens can affect the camera's ...


16

Many confused answers here... Eruditass got it right, it's all about the viewfinder. Actually it's mostly the "ground" glass, which is not a ground glass anymore: it's a microstructured glass, optimized for light transmission with slow lenses, not for ease of manual focusing. Something a bit like a Fresnel lens. The eyesight, has nothing to do with this ...


12

On a reflex camera (those with a mirror allowing you to compose and focus through the same lens that you will shoot the picture - aka SLR or DSLR) the focussing screen is a glass surface on which the image is projected by the mirror. You can see it by removing the lens and looking inside the body above the mirror: When looking into the viewfinder you see ...


12

Actually, the default screen is imprecise. With the advent of autofocus, modern viewfinder screens are designed to be bright even with slow lenses, at the cost of not really showing the difference in focus at fast apertures. With the "imprecise" screen, it's hard to see the exact, "critical" focus needed for fast lenses. But autofocus doesn't care, so if ...


10

What you are showing isn't just a focusing screen. It is a focusing screen with two special focusing aids. First, it has a split prism, which works as a tiny rangefinder — when the two sides are aligned, the subject is in focus. Second, outside of that, the rough microprism ring gives a similar effect, with a different tradeoff between ease of focus and ...


8

Well, first I should mention that dust on the focusing screen has no effect on the image quality or the exposure metering, so for that sake there is no need to clean it. On the other hand the dust may get loose and get onto the sensor, so it's a good preventive measure tog get the worst dust away at least. To clean it, you should first turn the camera off, ...


8

Two things contribute to this phenomenon: The light collected by split image focusing screens are edge rays collected on the outer areas of the front element of the lens. With lenses that have smaller maximum apertures the focusing screen is trying to find light from an area wider than the front element of the lens. In most situations focusing and metering ...


7

Split-prism focusing screens went away with AF. I have a Nikon F90 from the early 90s with a plain matte screen (and only one focus area). I can't speak for other brands and models, AF film bodies being the red-headed stepchildren of the used gear market. They're cheap because no-one wants them. I think the reasons for not having them are both usability - a ...


7

It sounds like you're observing the laser etched glass focussing screen. A focusing screen requires a rough surface so an image can be formed for you to view through the viewfinder. Ground glass used to be used for this purpose but now glass etched in a circular pattern with a laser is used, to improve the brightness of the viewfinder when used with slower ...


6

That's a 'focusing screen'. You can easily obtain it either from the manufacturer directly, or from a camera store. For example from Adorama Typically, for one model of camera there will be a few types of focusing screens that work with it. Your camera's manual will tell you which one has been installed by default, and which ones you can substitute for ...


6

These focusing aids are part of the focusing screen, which is part of the viewing system within the camera body. Some cameras have user-interchangeable focusing screens, others have factory-interchangeable focusing screens, and some cameras have focusing screens that cannot be changed. See for example Canon's leaflet on focusing screens here: https://www....


5

You'll find most split-circle focusing screens in manual focus film SLRs. In these cameras, the mirror is very efficient, and reflects all of the light up into the viewfinder. A little gets diverted for the exposure metering, but most of the light goes up and hits the focus screen. On autofocusing cameras the mirror is less efficient, as part of the light ...


5

The first thing to tackle is keeping all your focusing screens (and equipment used to handle them) tidy. Any dirt will be clearly visible in viewfinder and somewhat hard to remove from the ground side of the glass. Often a focusing screen kit has tweezers and a finger-protection glove (like a tiny condom, to protect the glass from body grease) to assist ...


5

The physics... The ground glass (or plastic) screen acts as a diffuser, scattering light passing through it randomly rather than simply letting it pass through unaffected. An image can be brought to focus on the screen by adjusting the lens, and the image we perceive comes from scattered light that is traveling in the precise direction of our retinas. The ...


4

This is due to the focusing screen, which is a small piece of etched glass above the mirror and below the pentaprism/pentamirror, is misaligned. I've had this problem a couple times with my 450D, as I've had to take my focusing screen out on a couple occasions to clean it due to some thing getting thoroughly stuck on it. After reinserting the screen, my ...


4

It's to do with the focussing screen, however I don't profess to completely understand all of the effects you mentioned. The focussing screen in modern DSLRs is made of laser etched glass in order to facilitate manual focussing and transmit as much light as possible for slow lenses. With old fashioned ground glass screens, the micro-structure of the glass ...


4

From what I can find, the 60D has the same focusing screen as 40D and 50D, and it looks quite different from the one in the 550D (T2i) so it's not likely that it will fit: 40D/50D custom focusing screen replacement 550D custom focusing screen replacement According to the Canon specs, the 550D focusing screen is not replaceable, although there are third ...


4

You are looking for an HDMI monitor. Here you go, BHPHoto has 116 results for that.


4

The ground glass, or focusing screen, is, in the simplest case, literally just a piece of glass that has been ground, so one of its sides has a rough/matte surface (see also the article Ground glass on Wikipedia. It's actually quite easy (at least for large format cameras) to make ground glass yourself, see this how-to for example. The ground glass just ...


4

Sounds to me like you've never actually used a different focus screen on your 6D, and you're obsessing about something you've read online. Just get the super-precision matte screen (Eg-S). I've adapted manual focus lenses to both my 5DMkII and 50D--both of which have the same interchangeable focus screen feature your 6D does. Swapping the focus screen is ...


3

The great news is that you have not damaged anything, this is normal. The screen fits between the prism and the sensors and so it will affect something. Using KatzEye screens as an example because I have personal experience on two Nikons, each has good notes on what kind of metering changes you will experience. Mostly your exposure will change by a ...


3

It can and it does. The metering sensors are placed up in the top of the prism housing, in other words it reads the light AFTER the light has passed through the focusing screen. If you are using a camera that is designed to have different mattes replaced (bad news: You are not) and the screen is one the camera is designed for, the necessary adjustments that ...


3

You can always remove the focusing screen then puff some air on it with a blower or whatever. Here's a website with instructions on how to remove the focus screen. http://www.focusingscreen.com/work/550den.htm You may simply end up with more dust though. Who knows. Good luck!


3

I'm not exactly sure what you mean, I am guessing that by 180 you mean a single split, perhaps horizontally framed and the double 45 is really an X shaped dual split. The reason that the old SLRs had so many different screens is that its very much a personal preference, there is no one answer, it varies by photographer by what they are shooting. I ...


3

A scratch on the focusing screen won't affect Auto Focus at all, since the light used for AF, whether phase detection or contrast detection, doesn't pass through the focusing screen. It will only affect what you see through the viewfinder. If severe enough it might affect metering, which does use light that passes through the focusing screen. But a single ...


3

I would suggest rather than drawing directly on the ground glass focusing screen that you use a piece of clear laminate material to draw on. If you draw your desired lines onto paper, tape the plastic over the paper then trace your markings onto the laminate, you can try several different options depending on what you need. Once you find the perfect ...


3

If the focusing aid was part of the lens, it would be visible in the image. That's because they are optical elements themselves, which means they change the properties of the light that goes through them in order to work. But you do not want them to be visible in the frame (neither film nor digital). The path of light goes always trough the lens and then ...


2

On the installation instructions at: http://www.focusingscreen.com/work/k7en.htm there is the statement: Penatx [sic] ISTD/K7/K10D/K20D change focusingscreen will not influence AF-Focus and focus point operate. So it seems to be working with autofocus.



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