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These cheap 420-800 zooms, any info/review?
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PostPosted: Mon Jun 29, 2015 12:55 pm    Post subject: These cheap 420-800 zooms, any info/review? Reply with quote
I have two questions, did anyone ever tested or has samples from such lenses:

http://www.amazon.com/Opteka-420-800mm-Telephoto-Digital-Cameras/dp/B00OACMWJ6

and 2nd, as description says, this is "4 Elements in 2 groups" lens design. I highly doubt that it will be Tessar design, more likely just two doublets. So here's the main question - "zoom" here is achieved by moving front element away from rear element. So what if I'll take fixed 500mm F8 lens and move it's front element further away, will I get the same effect?


PostPosted: Mon Jun 29, 2015 1:24 pm    Post subject: Reply with quote
I discovered that in an old 35mm compact zoom camera, the zoom elements just move forward and backwards in front of a fixed lens. The fixed lens appears to be the one doing the focusing. In the Canon that I dismantled the fixed lens was 38mm and the zoom was 2x. This lens too appeared to be a 4-element 2 group design.

I don't trust any lens that calls itself 'digitally optimised' and 'HD'. They are meaningless words, and in my experience indicate low quality. Like 'optical' lenses. I have had many of these - sometimes expensive- type of lenses come through my hands when buying collections. Absolutely zero are any good. Though I've not had one of these.

In my honest opinion; It is unlikely to give results much better than simply using a good 300 or 400mm lens and cropping. CA would be visible.

However, it appears to have gotten some good reviews on Amazon. I guess they'd edit out the negative ones. All reviews mention the difficulty of focusing (caused by camera shake, dim viewfinder image and shallow DOF).

You pays your money...


PostPosted: Mon Jun 29, 2015 2:49 pm    Post subject: Reply with quote
In my case camera shake and dim viewfinder would not be an issue, since using on tripod, on Sony camera with IS built in body and live view.


PostPosted: Mon Jun 29, 2015 4:43 pm    Post subject: Reply with quote
philslizzy wrote:
I discovered that in an old 35mm compact zoom camera, the zoom elements just move forward and backwards in front of a fixed lens. The fixed lens appears to be the one doing the focusing. In the Canon that I dismantled the fixed lens was 38mm and the zoom was 2x. This lens too appeared to be a 4-element 2 group design.

I don't trust any lens that calls itself 'digitally optimised' and 'HD'. They are meaningless words, and in my experience indicate low quality. Like 'optical' lenses. I have had many of these - sometimes expensive- type of lenses come through my hands when buying collections. Absolutely zero are any good. Though I've not had one of these.

In my honest opinion; It is unlikely to give results much better than simply using a good 300 or 400mm lens and cropping. CA would be visible.

However, it appears to have gotten some good reviews on Amazon. I guess they'd edit out the negative ones. All reviews mention the difficulty of focusing (caused by camera shake, dim viewfinder image and shallow DOF).

You pays your money...

+1


PostPosted: Mon Jun 29, 2015 4:44 pm    Post subject: Reply with quote
Shake will still be an issue, don't expect steadyshot to do much on such a long lens that isn't communicating with the body.

For example, at 500mm, on an APS-C body, you will need at least 1/750 even with the thing on a tripod. 1/750, f8 will probably mean turning up the ISO unless the light is very bright.


PostPosted: Mon Jun 29, 2015 4:48 pm    Post subject: Reply with quote
it will takes pictures of course ,but after first humm pretty good feeling, you will not use it more at all I beleive it. Subject for long lenses rarely stay on sunshine , so F8.3 will be not enough, from long lenses I was really happy only with MC Rubinar 500mm f5.6 , others are either heavy , big or low quality lenses as well.


PostPosted: Mon Jun 29, 2015 5:56 pm    Post subject: Reply with quote
I'm using chipped T2 adapter, which allows full functionality, including focus peaking, etc.

I have experience of using 1000mm lens with Sony cameras and found no significant issues

Generally I shoot at 1/500 or faster, F16, ISO400.

So please, if anyone can provide user experience of such lenses with samples, especially at tele end - you're very welcome.


PostPosted: Mon Jun 29, 2015 6:25 pm    Post subject: Reply with quote
400mm is perfectly usable handheld with Pentax APS-C bodies IS at f/8
Even on moving subjects - like aircraft.
Very usable on closeup subjects like birds.

Longer than that is quite a lot harder.

There are some common 400mm f/6.3 lenses around that are pretty decent and very inexpensive, if you are looking for something along those lines I would try for a cheap 400/6.3 Spiratone or Astranar or the like. $20 will get you right on the very steep long tele learning curve.

That 420-800 seems to be a very early sort of zoom, a varifocal.
These things go back to the 1890's.
It also has a fixed aperture (no iris), so the effective f/stop varies with the focal length.
Focal length is changed by varying the distance between the front and back group.

I don't think it would be all that bad, especially for center sharpness.

Some comments here -
http://www.dpreview.com/forums/thread/1248210


PostPosted: Mon Jun 29, 2015 7:00 pm    Post subject: Reply with quote
philslizzy wrote:

However, it appears to have gotten some good reviews on Amazon. I guess they'd edit out the negative ones. All reviews mention the difficulty of focusing (caused by camera shake, dim viewfinder image and shallow DOF).



Amazon does NOT edit out negative reviews. On several occasions, I've changed buying decisions of products because of the number of negative reviews they had received.

One thing the Amazon page on this lens does not tell you is this zoom is a variable aperture zoom. It's f/8.3 at 420mm, but it's f/16 at 800mm. AND there are no aperture blades -- so this is more like shooting with a mirror than with a regular refractor lens. And a slow mirror at that. Now, for me, f/16 is just a bit too dim, especially if one is wanting to capture the moon with it. However, it appears that it is possible at least because, in one of the reviews at Amazon, an owner mentioned he obtained sharp pics of the moon with it.

The Amazon page also is advertizing it as a 420-1600mm zoom, which means they must be tossing in a cheap 2x TC with the lens. So if it's f/16 at 800mm, then it will be a whoppingly dim f/32 at 1600mm!


PostPosted: Mon Jun 29, 2015 7:39 pm    Post subject: Reply with quote
Sample, sample @ 800mm! Smile less theory please Smile

p.s. while amazon does not edits out negative reviews, seller might contact you asking to delete negative review for refund or discount or whatsoever - I had personal experience of that on amazon.


PostPosted: Mon Jun 29, 2015 11:49 pm    Post subject: Reply with quote
CuriousOne wrote:
Sample, sample @ 800mm! Smile less theory please Smile

p.s. while amazon does not edits out negative reviews, seller might contact you asking to delete negative review for refund or discount or whatsoever - I had personal experience of that on amazon.


You're talking about one of Amazon's sellers, and not Amazon, correct? I consider that practice to be unethical.

I have actually come across products on Amazon that had more bad reviews than positive reviews, and of course my question when I saw this was, "Why do they carry such an inferior product at all?" Too big to notice or care, I suppose, which is why reviews are so important and should never be influenced.

Hey, I wrote a book about camera gear that was sold on Amazon for years -- in fact, it's still available as an ebook -- and I had to take the knocks with the praise, and there were a few knocks, too. But that's life, and it helps you make a better product if the criticisms are well-founded. In my case, they weren't, but perhaps I'm being partial . . . Cool You can see my book here:
http://www.amazon.com/McBrooms-Camera-Bluebook-Michael-McBroom/dp/1584280131/ref=sr_1_1?ie=UTF8&qid=1435621847&sr=8-1&keywords=mcbroom%27s+camera+bluebook


Oh, and if you're intersted in seeing samples from the 420-800mm zoom, try Flickr. I just went there and typed in "420-800" and got a bunch of hits. Here's one I found at random, and there were better ones than this:

House Sparrow by Kathryn Docking, on Flickr


PostPosted: Tue Jun 30, 2015 3:13 am    Post subject: Reply with quote
Yes sellers, but amazon can also do nearly the same. They remove product, and re-list it under new ASIN or how it's called. So, your negative review is not visible to anyone. In fact, in your reviews history, you will see "No item title" and "No item description available" for such blocked item.

I had a review of ATTEN power supply, sold by amazon itself and having some constant issues. There was huge storm of feedbacks on that review, and suddenly product disappeared!


PostPosted: Tue Jun 30, 2015 4:34 am    Post subject: Reply with quote
Well, you say "disappeared," but what probably happened was Amazon just decided to drop the item because of all the bad feedback. Nothing wrong with that. It was worthless, so they got rid of it. I'd do the same.
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