Manual Focus in this day and age?

[DonSchap]

Yes. Even though most DSLR cameras are designed without manual focusing grids, there are a number of this grids available which can assist you in making a manual focus, when autofocus is just not there for you.

When does autofocus NOT work?

One argument holds that most people are going to try and get a lot more out of their lenses than the these devices were designed to do. It is called “stretching a buck” … and believe me, a lot of hobbyists do it. Indulge me here:

Let’s say, just for argument sake, you purchase a typical SONY or TAMRON AF 70-300mm f/4-5.6 starter lens for your camera. Oh, why look, there’s one in your lens case. Who knew? Anyway, obviously you are going to want to have a longer lens and cannot afford it. That $800 price tag is rather brutal looking. So, you find yourself looking for a “cost-effective” way to extend what you already have. So you go out and buy either a rather low cost 1.4x or a 2x T/C (Teleconverter) (say $100 or so) … slap it on the end of your 70-300mm and, Voila, you now have a 98-420mm or 140-600mm lens, right? Sure. The math is correct.

70 x 1.4 = 98
300 x 1.4 = 420

70 x 2 = 140
300 x 2 = 600

Wow, that was easy. Unfortunately, by doing so, there is a stiff light penalty to this (not taking into account the image degradation by adding more glass into the picture).

Light Penalties
The 1.4x T/C = loss of 1 f/stop worth of light
The 2x T/C = loss of 2 f/stops worth of light

Okay, so here’s the real problem we are dealing with. You need to realize that most camera autofocus systems begin to fail when the lens’ base aperture reaches around f/6.3 –f/7.1 (the base aperture is usually stamped on the outside of every lens body and is on the outside of lens’ box).

So, let’s do the math for this:

a) At 300mm, the base aperture of your lens alone is f/5.6. You cannot make this wider, it is what it is. Anything you add to the lens only makes it worse.
b) Okay, so now you ADD the full f/stop “light penalty” by attaching the 1.4x T/C to the lens
c) The base aperture of the whole lens has just leapt to … f/8
d) Guess what? Yeah, no AF lock! It’ll just drift back and forth, unable to stop, until it gives up.

This is precisely where an enhanced MANUAL FOCUSING SCREEN can help. You switch the AF Mode in your camera to MF Mode and then you will not have to fight the autofocus system, as it saws its way back and forth, unable to achieve a focus and wasting valuable battery power. You simple adjust the focusing ring on the lens, as you look through the viewfinder and get your own “lock.”

This is just one reason for using this enhanced screen. Another is not being able to achieve autofocus due to difficult lighting situations. Although focus can be tricky in manual, under less than optimum lighting, you usually can “creep it” close enough to turn out something useful. The manual focusing screen helps as it improves the sharpness your eye will see.

There are a number good MANUAL focus lenses out there and they can have significant cost savings, if you are willing to forego the hardware involved in an autofocus lens. Also, MANUAL focus will often allow you to use older lenses, which may not have ever been designed with autofocus capability, e.g., TAMRON’s Adaptall2 series lenses or the current SamYang {aka Boker, Polar, Vivitar, Falcon, Rokinon} (South Korean) lenses. These can offer decent images … without the enormous cost of investing in high-end, wide aperture glass. You just have to be a little more involved in your focusing and forget your old “point & shoot” habits. :thumbsup:

[Frog]

I've considered a manual focus grid and have no idea why they are no longer in cameras.
Something technical I'm sure that is unknown to me, but if you can buy a grid then there shouldn't be a problem
I have read/heard that they can cause problems with the auto-focus, especially when using spot focus. True?

[SmartWombat]

If it's a split prism screen then yes, the split prism messes up the central AF and spot metering quite comprehensively.
Same goes for a microprism grid, often arranged as a ring around the central prism pair.

Modern AF lenses don't have the feel of a real connection between the focus ring and the lens, I find them pretty uncertian in focussing.
For MF I would want to use an old manual lens, where the focussing was directly driven by the focus ring not an intermediary electronic system.

[DonSchap]

Here's a recent MANUAL focus entry that I recently acquired, the Rokinon MF 85mm f/1.4 from Cameta..

Does a right nice job, too, for a mere $250 USD

[PWhite214]

I am not sure how much trouble it is to change the focus screen, but a split image focus screen is listed on EBAY at $20.00 US. I might try one if I get some other projects done.

Phil

[Frog]

I suggest doing some research first, Phil.
You get what you pay for.

[DonSchap]

Frog ... take a look at the Hasselblad H4D ... and you will see that there is a lot more truth to what you say. You can pay ... and pay .. and pay.

[pisco]

It's easy to add a focusing screen. I've been looking at them for a while. Haoda http://haodascreen.com/default.aspx sell them for about $ 75, and If you google you'll find another with step by step pictures on how to change it.

A couple of weeks ago I was playing with the camera and by mistake I removed the screen that comes with the camera... took me 5-10 minutes to google the step by step pictures and put it back on.

[PWhite214]

Sounds good, I have to manual focus with my bellows (MD mount) with my old MD mount lenses. With my aging eyes I have trouble focusing with the stock Sony Screen. Thanks for the information.

Phil