OVF vs EVF put to rest

Started Sep 16, 2012 | Discussions thread
Piginho Regular Member • Posts: 317
Re: OVF vs EVF put to rest

TrojMacReady wrote:

Piginho wrote:

TrojMacReady wrote:

Piginho wrote:

TrojMacReady wrote:

No OVF with ground glass will be able to show you detail equivalent of each pixel in say the final 24MP image, regardless of how good your eyes are. An EVF can, regardless of its resolution, as long as there's a quick magnification button that allows you to magnify up to pixel level (of the sensor).

And from where have you derived these facts? Please provide links/references!

Here's one simplified explanation and example:


This doesn't answer the question in any way, though it was an interesting read. Also, ground glass screens haven't been used in SLRs or DSLRs for more than 30 years. Viewfinder screens are plastic and some are fresnel type. Minolta were at the forefront of this technology and most recently in Sony implementation used spherical acute matte screens.

Is this a discussion of semantics or one with substance? Of course they are no longer made of real glass, but most people still refer to them as ground glass. Glasses that people wear are often made of plastics too, are you going to correct people calling them glasses still?

The closest that I could get to any kind of information regarding resolving power is in the following link.


It has to be born in mind that this link is talking about ground glass, but a simple calculation would indicate at least 9Mp resolution should be possible. How this relates to the more modern screens in a Sony A900 for example, I cannot say, as the information seems to be unavailable. What makes me laugh is your assertion that "No OVF with ground glass will be able to show you the detail equivalent of each pixel in say the final 24MP image," when you have no definitive evidence to back this claim.

You mean I have 20/12.5 vision and actually compared them (the A900 is still the OVF benchmarks for DSLR's) rather than your theorizing and assumptions about EVF's? Yes, you're funny like that at times.

As it happens, you may be right, but that's yet to be determined.

You mean you have yet to make the comparison yourself, apparently.

What is almost certainly true, based on the research that I've done so far, is that the OVF in an A900 or similar will have at least around 4 X the resolving power of a 2.4Mp EVF.

Do share the exact calculations you used and all the variables involved.

Also, by posting your link and some of your latest comments, you are attempting to move the goalposts of the debate. You're trying to make it about DOF and how it's seen in the viewfinder. What's the title of this thread?

I first reacted to someone making claims about DOF preview, suggesting they are similar in their representation of DOF (preview). That was you. The rest of that discussion wasn't with you.

My question to you was about the source of your knowledge about resolution on GG screens, not DOF issues.

You asked what the claim that GG limits the resolution, is based on. I said experience and gave an example. You're in the process of admitting it's true.

After that question, I didn't reply to you any further about DOF issues. Have you activated the posting tree or are you staring at a flat view of the forums?

The link you provided as an answer to my question about how you can to have knowledge that a GG screen couldn't resolve 24MP, had nothing to do with the question. Yes, it did relate to DOF as seen on a ground glass screen, which is something that I have also referred to, but it had nothing to do with resolving power, which if you go back far enough on this and similar threads, has been my personal issue with EVF to date. Others have different issues with it.

You now say that experience is your credible support for your claims about ground glass screens. I would say get your eyes tested because my experience is different. This is just anecdotal from both of us. I'm talking about either scientific evidence, or at least credible specification information from the manufacturers.

As for my simple calculation. If you bothered to read the link that I gave you, like I read the one that you gave me, you will see some experimentation that showed the equivalent of 18Mp resolution on a GG screen exactly twice the size of A900 screen. From this I deduced a mimimum of 9Mp on A900 and this is not allowing for improvements due to spherical acute matte design. Also GG screens resolve detail differently according to how finely they are ground. Course ground provides more contrast but less resolution and fine ground is the opposite.

Therefore, there are quite a few variables to take into account and unless someone has the hard data we can't be certain, however, if you read the article that I suggested, I'm sure that you'll agree that 9Mp + is probably a conservative estimate, taking into consideration Minolta and then Sony's lead in development in modern focussing screens. Hence, 4 X 2.4 = 9.6Mp.

As for DOF issues, I was not unaware of the points brought out in your linked article. In fact, it's one of the reasons that Sony provided different screens for the A900. Even with the most appropriate screen, however, you will still see DOF on screen with 50mm set at f1.4, looking like about f2.8, but this relationship is not linear. With lens at f2.8, it looks as it should and will continue to do so at higher apertures.

Again, I pointed to use of intelligent preview on A900 as a solution at large apertures.

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