Telephoto multiplier lens or Rokinon 500mm mirror lens ?

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plainman007

Well-known member
Hi,

I have a canon 55-250 IS telephoto lens. I saw some adapter lenses on ebay with a 3.5x conversion factor. Which you fit onto the front of your lens to multiply its focal length. My second option is a seperate rokinon or opteka 500mm mirror lens. Which will give better image quality when used on my 550d ?

Please keep in mind that i mostly use my camera only for video. And ive heard that lens quality hits on the image quality are not as obvious on video as they are in images that are subject to keen scrutiny.

Id like to know which would be a better option.

Thanks...
 
your font is really large, you should try making it smaller

plainman007 said:
ive heard that lens quality hits on the image quality are not as obvious on video as they are in images that are subject to keen scrutiny.
Click to expand...

If nothing else, this site is all about keen scrutiny of video image quality. That being said the adverse effects of both lenses will be quit noticable on both still photos and DSLR video. Some people debate that lens sharpness isn't as important on DSLRs because its only HD resolution and even the worst 35mm lenses can ressolve that but this argument is false since canon DSLRs don't downres a full MP count but rather produce HD video by line skipping.

I don't know that exact multiplier but I can imagine you will loose tons of sharpness as well as probably have poor contrast and corner sharpness do to the glass on the multiplier. You might also experience vignetting.

The mirror lense is going to be terrible for anything but shooting the moon..and even that won't be great. The bokeh on mirror lenses is pretty gross (donut shaped), the aperture is fixed and slow, contrast is poor and sharpness is middle of the road.

If I had to choose, I would go with the multiplier but if I were you, I would spend on a more expensive lens or rent until I could afford to buy.

What will you be using this for anyway? 250 on a 550D is around 375mm..that has some pretty good reach.
 
Hi,

Thanks for the reply. I dont see what you mean about my font being big. It was normal sized when i posted and is normal right now (exact same size and font as your text) as im looking at it right now ? I really cant seem to understand why some webpages act quirky. For example right after the update and revamp of the dvx site the main forums list and thread list fonts seem very large. Right now if i back out of this thread to see whats on the main thread the fonts are gigantic. :(. Font size setting shows as 3 right now as im typing this post. I dont know how large this would look after i post. So id have to plead not guilty.

I know this site (or video forums to be specific) are ALSO about keen scrutiny of image quality. That being said im posting on a still photography forum and what i meant was that ive read reviews and from quite a lot of HDSLR video guys that a mediocre lens will show its effects more obvioulsy on a hi-res photograph even more so when zoomed and analyzed. But im sure it must be showing its effects on HD Video too but maybe less pronounced ?

Im aware of the downscaling being done using line skipping which sometimes contributes to the moire and aliasing issues when shooting synchronous patterned objects etc etc etc.

What about the option of using an extension tube ?

Yes im aware that a 250mm is good focal range on a 550d. But i recently tried with some wildlife subjects and wished i had more zoom. I could get a tiger to fill only about 20% of the frame at 250mm. Hence im thinking a little more might be better. But it doesnt warrant buying or renting since none of my work is for paid gigs. I have a 500d and the 550d. Planning to buy the 7D next year. Hence cant splurge too much on the lenses now.
 
Perhaps a GH2 with the focal multiplier would be a good choice, you could get a really amazingly long zoom with decent IS. I'm not sure you would be happy with a 500mm mirror lens or a 3.5 converter.
 
Just check vimeo and type in 'rokinon 500mm', youd be surprised, some of the vids are of decent quality considering what you pay for this lens.
 
If you can deal with the fixed and slow aperture as well as the donut shaped bokeh and poor contrast then by all means don't spend on a more expensive lens. Mirror lenses are around because they are suitable for certain applications. For my purposes I don't think it would be a wise investment to spend on one of these lenses as tempting as the focal length is. The bokeh is just too distracting and not being able to control dof is very hard to work with. I would think these two issues would be deal breakers for most wildlife photography.
 
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