Make a viewfinder- but the opposite- Help with lens..

[Opcod]

Hi

So i would like the make a viewfinder with an eyecup and see perfectly. But the source has to be a square lcd of 2.5 inch.. So i know if i just look in a teleconverter for any camera, the effect look almost what i whant to make.

So any expert to help me.. do i need some achromat, biconvex lens, diopter... Also, i know Hoodman have a product..

http://www.hoodmanusa.com/products.asp?dept=1017

But how to made something more powerfull..

Thanks in advance for hints.

* i use a camera that don't have a viewfinder, i whant to made one from the lcd.

[TCav]

With an optical viewfinder, the limit to the quality of the image you see is the quality of your vision.

LCD viewfinders havea much lower resolution than that, and when you start magnifying it, you're going to give up the image in favor of the pixels.

A 2.5 inch LCD viewfinder is 1.5" by 2", has an aspect ratio of 4:3, and usually contains ~230,000 pixels. That works out to a resolution of about 560 pixels wide by 420 pixels high. Just to keep the math simple, let's suppose that the camera has a 6MP image sensor that creates 3000x2000 images. So the LCD viewfinder must display the 3000 pixels of the imageonto 560 of its pixels, and 2000 pixels of the imageon 373 of its pixels. (It doesn't use the full 420 pixels becuase it needs to preserve the photo's 3:2 aspect ratio on the4:3 aspect ratio of the LCD display.) That means that each pixel on the LCD viewfinder is being used to display ~29 pixels from the actual image. So the LCD viewfinder shows a pretty poor version of the image anyway.

And you want to magnify it? You may not like what you see.

Most digicams have the ability to zoom in on photos stored on the flash memory card, but I don't know any that allow you to magnify the live image. You might be able to use the digital zoom, but digital zoom usually only kicks in after you've reached the limit of the optical zoom.

I think the HoodLoupe is the closest thing you're going to find.

[Alan T]

Opcod wrote:

i would like the make a viewfinder with an eyecup and see perfectly.....But how to made something more powerful...

Given the poor quality of the image anyway, you won't manage a much better optical device than this, my own invention, heavily used until Iacquired my new camera with a wonderful electronic viewfinder. Isuspect it may be a little cheaper than more sophisticated devices.

[Opcod]

Thank for the hint.

Also, Alan, how long does it have ? Because, i'm building a 35mm adapter for a small cam and all the box in fiberglass. So for stability purpuse.. i need a point in my face and see at the same time. I will post my developpement in about 2 week, maybe it can help other.

[shene]

There are viewfinders made for rangefinder cameras available on eBay (e.g., Argus, Kiev, Zeiss, Leica, etc). Some of them support 28mm, 35mm, 50mm, 100mm and 135mm (e.g., Kiev, Zeiss). Most of these viewfinders have parallax adjustment mechanism. However, you will need a hotshoe to mount this type of VF's.



CK

http://www.cs.mtu.edu/~shene/DigiCam

Nikon Coolpix 950/990/995/2500/4500/5700, Panasonic FZ-10/FZ-30, and Canon A95 User Guides

[[email protected]]

Maybe this is an alternative for you.

I hold the camera like an old-fashioned medium format reflex camera with my elbows jammed into my sides. This puts the LCD far enuf from the eye that you can see it while holding the camera steady.

It also helps taking candid pictures as subjects aren't aware you are looking at them.

Also CK Shene's recommendation is a good one. If you don't have a hot-shoe just glue the viewfinder to the camera body.

Dave

[Opcod]

Hi

So.. hum.. great. i think that idea have to be tried. But, at the same time, i got the Hoodman loupe. I will try all together next week. And i got all my stuff for make my mold out of fiberglass.