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Author Topic: Excellent shorter lens with TC vs Average longer lens  (Read 3930 times)

Hillsilly

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Excellent shorter lens with TC vs Average longer lens
« on: October 02, 2012, 07:42:22 AM »
Was just checking the Samyang site and see they've got an 800mm mirror lens and a 650-1300mm zoom.  A second hand shop near my work has a Meade 1000mm f/11 mirror lens for sale.  And I see a lot of similar lenses for sale on eBay.  A quick google search suggests the image quality from these lenses isn't great.  Unfortunately...it seems you get what you pay for.   

But my question is this: -

If you had a 300mm f/4, would your cropped image appear sharper than a cheap 1000mm+ lens?  What about a 300mm with a teleconverter or two?  Is there any point to buying a cheaper, longer lens?
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Excellent shorter lens with TC vs Average longer lens
« on: October 02, 2012, 07:42:22 AM »

neuroanatomist

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Re: Excellent shorter lens with TC vs Average longer lens
« Reply #1 on: October 02, 2012, 08:40:30 AM »
If you had a 300mm f/4, would your cropped image appear sharper than a cheap 1000mm+ lens?

I can't speak for a comparison based on optics, but I can tell you that manually focusing at 1280mm FF-equivalent (100-400 + 2x TC on APS-C) is really damn hard, even on a stable tripod and with IS (albeit only 2 stops).  The 300/4 image would at least be in sharp focus before cropping, whereas the 1000mm+ lens would likely not be...
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TrumpetPower!

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Re: Excellent shorter lens with TC vs Average longer lens
« Reply #2 on: October 02, 2012, 10:03:34 AM »
Unless you're an astronomer or in the espionage business, there's very little real-world utility to lenses longer than about 800 mm. The most common case would be birding...but a successful bird photographer knows how to get close enough to the subjects to use a "normal" supertelephoto.

The 300 f/4 is an excellent lens. It's a bit short and slow for birding; if you'd have a teleconverter permanently attached, strongly consider the 400 f/5.6 instead.

You're always going to get the best results with a larger sensor and a (quality) lens that's (natively) long enough to properly frame your subject. But, if you're distance-limited...well, at first, it's a tossup between a (quality) 1.4x teleconverter and an APS-C body with higher pixel density. Some combinations will be better than others. If you're still distance-limited in such a situation, your only choice left is both. And if you still need to significantly crop with a teleconverter on a crop body, then either you need to get closer to your subject or you need better equipment or you're in the worng line of work.

Of course, what you're doing with the final output is a question, as well. If all you're looking for is something to post on BookFace, then you can settle for a lot less than if you're on assignment for <i>National Geographic.</i>

Cheers,

b&

Hillsilly

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Re: Excellent shorter lens with TC vs Average longer lens
« Reply #3 on: October 02, 2012, 10:47:42 AM »
Thanks, should have mentioned that my interest is mostly astronomy related.  Currently using a 400mm with two 2x teleconverters on an m4/3 cameras (to give me an effective 3200mm).  But getting annoyed with noise and my photos could be sharper (and probably my tripod more stable).  Plus the small aperture doesn't help with getting sharp images.  Its not a bad set up for bright objects such as the moon, but planets look like tiny fuzzy blobs.  Just daydreaming about other options.  Maybe a telescope is the solution.
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Mt Spokane Photography

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Re: Excellent shorter lens with TC vs Average longer lens
« Reply #4 on: October 02, 2012, 11:39:14 AM »
One of the big issues with mirror lenses is the background.  The subject may be sharp enough, but out of focus areas are horrible.  For astronomy, thats likely no issue, but otherwise, the 300mm f/4 might produce a nicer lookiing image.
600mm Sigma Mirror lens (one of the best)  Only the center is sharp, Notice the background!

 
500mm Nikon mirror lens (Also one of the best)  Notice the weird background)
 

 
 
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300mm f/4L 100 % crop still sharp!

well_dunno

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Re: Excellent shorter lens with TC vs Average longer lens
« Reply #5 on: October 02, 2012, 11:58:18 AM »
If you had a 300mm f/4, would your cropped image appear sharper than a cheap 1000mm+ lens?

I can't speak for a comparison based on optics, but I can tell you that manually focusing at 1280mm FF-equivalent (100-400 + 2x TC on APS-C) is really damn hard, even on a stable tripod and with IS (albeit only 2 stops).  The 300/4 image would at least be in sharp focus before cropping, whereas the 1000mm+ lens would likely not be...

+1
I tried 70-300 with kenko 3X going up to 900mm on a tripod, with the slightest touch, everything moves significantly so I ended up blindly adjusting focus, waiting for the vibration to end, checking focus, if not achieved blindly adjusting again etc. Moon's movement did not help either and I gave up eventually...

I know jrista has some sharp shots with 2x + 1.4x on a 300 f/2.8. Perhaps he can share his experience...

Cheers!

TrumpetPower!

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Re: Excellent shorter lens with TC vs Average longer lens
« Reply #6 on: October 02, 2012, 12:35:21 PM »
Thanks, should have mentioned that my interest is mostly astronomy related.


In that case, forget entirely about SLR lenses. Instead, get yourself a decent (real!) astronomical telescope and whatever adapter you need to mount your camera to it.

Everything involves compromise. There are lots of compromises necessary for making photographic lenses that come at the expense of astronomical suitability, and vice-versa. An upside-down image is a non-starter for a photographic lens, but hardly even worth mentioning for a telescopic lens, for example. Pleasing (or, at least, not distracting) out-of-focus blur is necessary for a photographic lens, but not even remotely on the radar for astronomers.

You will get <i>far</i> more bang for your buck with an astronomical telescope than with a telephoto lens.

There are exceptions, of course...if you're looking for wide-angle shots, such as of the entire Milky Way, then you'll need a typical wide-angle photographic lens. And a Great White is going to do a pretty decent job at wide-field astrophotography...but a $12,000 telescope is going to do a much better job than a $12,000 400 f/2.8 II. Still, if you're wanting to do an automated search for extra-solar planets, you're probably going to go with an array of several 200 f/1.8s.

http://en.wikipedia.org/wiki/SuperWASP

Cheers,

b&

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Re: Excellent shorter lens with TC vs Average longer lens
« Reply #6 on: October 02, 2012, 12:35:21 PM »

emag

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Re: Excellent shorter lens with TC vs Average longer lens
« Reply #7 on: October 02, 2012, 01:53:28 PM »
I would recommend a good tracking mount be your next purchase.  A 300/4 will take some fine images of astronomical objects, but you'll need 30-90 second exposures in order to use lower ISO settings for less noise.  The beauty of using a telephoto lens for a beginning foray into astrophotography is that you have a lens useful for other photography.  A telescope is somewhat less versatile.  I shoot with a Canon 300/4, Sigma 400/5.6, Sigma 70-200/2.8 and several telescopes.  I have a 500/8 mirror lens I bought for a song that I've never used for astro.....that'll change soon.

This was a shot taken during a public stargaze last fall, single shot with minimal post-processing.  Modified 40D with EF 300/4.


Menace

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Re: Excellent shorter lens with TC vs Average longer lens
« Reply #8 on: October 14, 2012, 09:54:17 PM »
I think a decent telescope would be a better investment for your astronomy photography. Cheers
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Radiating

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Re: Excellent shorter lens with TC vs Average longer lens
« Reply #9 on: October 15, 2012, 12:24:51 AM »
Was just checking the Samyang site and see they've got an 800mm mirror lens and a 650-1300mm zoom.  A second hand shop near my work has a Meade 1000mm f/11 mirror lens for sale.  And I see a lot of similar lenses for sale on eBay.  A quick google search suggests the image quality from these lenses isn't great.  Unfortunately...it seems you get what you pay for.   

But my question is this: -

If you had a 300mm f/4, would your cropped image appear sharper than a cheap 1000mm+ lens?  What about a 300mm with a teleconverter or two?  Is there any point to buying a cheaper, longer lens?


Well here's a comparison between the 300mm F/4.0 with a 2x teleconverter and a Canon 100-400mm with a 1.4x teleconverter. The image quality is similar:

http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=111&Camera=453&Sample=0&FLI=4&API=2&LensComp=113&CameraComp=453&SampleComp=0&FLIComp=10&APIComp=3

So let's assume that the image quality from the 100-400mm with a 2x teleconverter will be similar to a 300mm with a 2x teleconverter and a 1.4x teleconvterter. Giving us a 840mm f/9.0 lens.


Here's a comparison between the 100mm-400mm with a 2x teleconverter (our stand in for a 300 F4 with 2x & 1.4x) and the Tamron 180mm lens.


Tamron 180mm lens, a lens which people consider "good" compared to our stand in:

http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=393&Sample=0&FLI=0&API=0&LensComp=113&CameraComp=453&SampleComp=0&FLIComp=11&APIComp=3

As you can see our estimate of a 300mm F4 with a 2x & 1.4x teleconverter is better than what is considered a "good" lens.

Now lets compare our stand in to what is conservatively considered bad:

http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=683&Camera=453&Sample=0&FLI=6&API=2&LensComp=113&CameraComp=453&SampleComp=0&FLIComp=11&APIComp=3

Sigma 150-500mm with a 1.4x TC. The stand in does MUCH better.


I think you will see much better results with a 300mm F4 with dual teleconverters than you will see with a mirror lens that has a reputation for sub par image quality.

Hope that helps.

wickidwombat

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Re: Excellent shorter lens with TC vs Average longer lens
« Reply #10 on: October 15, 2012, 04:04:13 AM »
I went a different option and got a 600mm f4.5 canon FD lens off ebay $1500 in perfect condition and an edmika adapter, i'm still on the lookout for an FD TC for it but optically its awesome and almost 2 stops faster than the 300 f4L with 2x TC on it not to mention the 300f4L wit 2x will only AF on my 1D anyway the 5ds are all manual anyway

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Re: Excellent shorter lens with TC vs Average longer lens
« Reply #10 on: October 15, 2012, 04:04:13 AM »