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Lenses Discussion of Lenses

Question on Sharpness

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  #21  
Old 20-03-06, 19:38
prostie1200 prostie1200 is offline  
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Quote:
Originally Posted by robski
Make you wonder if something has worked loose ?
As long as its in the lens and not my head Robski, It'l be OK
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  #22  
Old 20-03-06, 21:07
Grant Grant is offline  
 
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Yelvertoft, thank you for the welcome; likewise Robski, and thank you for the info.

I use 6x7 film (what do you mean, “what’s that?”) and considering a decent telephoto. However, I need to translate your info into my format. Hence the interest.

As a minimum I will need to get a 400mm plus a 1.4 converter to give 560mm. In 6x7 terms, this will equate to about 280mm. Maybe that’s not enough. Looks like I will need to reconsider.

2x converter? Depends on the quality.

Grant.
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  #23  
Old 20-03-06, 21:38
robski robski is offline
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Grant

I used a 300mm plus the sensor 1.6 crop factor equates to 480mm in 35mm terms.

If I recall your standard lens is something like 150mm ?
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Last edited by robski; 20-03-06 at 21:40.
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  #24  
Old 20-03-06, 21:40
robski robski is offline
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Quote:
Originally Posted by prostie1200
As long as its in the lens and not my head Robski, It'l be OK
LOL - Now there's a thought
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  #25  
Old 21-03-06, 01:45
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nirofo nirofo is offline  
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Sounds to me as though there is something wrong with the lens, however, that shouldn't cause motion blur unless the electronics are sending the wrong signal to the camera, making the camera think you a need slower shutter speed than you should be getting! Even then, with the camera and lens locked down hard on a subtantial tripod you should be able to obtain sharp images of stationery subjects. That is providing of course you're using some sort of electronic shutter release and not manual.

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  #26  
Old 21-03-06, 02:16
Grant Grant is offline  
 
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Rob, there is a correction to my post, ie “In 6x7 terms” should be “In 35mm terms”. No matter.

I don’t have a standard lens but it’s 90mm.

If you’re using an effective focal length of 480mm, for comparable results I would need to go 2x this or nearly 1000mm (to convert 35mm equivalents just double the focal length).

My ignorance of digital cameras is almost total but does the film sensor area produce a raw image about 1.5x that of 35mm? If this is correct, then your figure of 480mm could be divided by 1.5 to give just over 300mm (320mm) in 35mm terms? It’s simpler for me to think in terms of 35mmm/6x7.

You may wonder why I’m so keen to pin this down. Simple, if I going to fork out around £1,300 for a second-hand lens (£7000 new) plus £250 for a used 1.4x (or 2x) converter, I need to know it will deliver the images. If not, I’ll save the money and enjoy the excellent shots on WPF.

I’ve just had a quick glance at your portfolio. Magnificent stuff, especially the jersey. Re the squirrel, the focal length is given as 300.0mm (35mm equivalent: 2245mm). Note 2245mm. Is this correct?

Thanks in advance.

Grant.
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  #27  
Old 21-03-06, 03:19
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Tyler Vargo Tyler Vargo is offline  
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Quote:
Originally Posted by Grant
the focal length is given as 300.0mm (35mm equivalent: 2245mm). Note 2245mm. Is this correct?
I can answer that one for you, the number is incorrect, highly!

That's a bug with the gallery software, it multiplied 300 by 7.48333... instead of the correct 1.6... It does that to a lot of the photos taken with the 20D.
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Last edited by Tyler Vargo; 21-03-06 at 03:22.
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  #28  
Old 21-03-06, 10:58
robski robski is offline
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Grant the Crop factor is due to the fact that many DSLR sensors are not full frame. 1.3 and 1.6 are common for Canon and 1.5 for Nikon. The bigger the sensor the harder it is to produce in reliable quantities and hence very expensive. If your into bird photography may you should thing about getting a DSLR it may be cheaper. Digital has pretty well caught up with film these days.
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Last edited by robski; 21-03-06 at 11:17.
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  #29  
Old 21-03-06, 13:12
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Don Hoey Don Hoey is offline  
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Quote:
Originally Posted by robski
Grant the Crop factor is due to the fact that many DSLR sensors are not full frame. 1.3 and 1.6 are common for Canon and 1.5 for Nikon. The bigger the sensor the harder it is to produce in reliable quantities and hence very expensive. If your into bird photography may you should thing about getting a DSLR it may be cheaper. Digital has pretty well caught up with film these days.
May be worth a look at this thread and the link on post 5. http://www.worldphotographyforum.com...read.php?t=689

Don
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  #30  
Old 21-03-06, 16:45
prostie1200 prostie1200 is offline  
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Thanks Nirofo

Your last post regarding Electronics spured me to take a look at the elecronic bayonet pins on the lens. They were furred and a gentle wash and bush up has made all the difference. - here's the first shot at 50 feet 500 at
f4, much improved dont you think.
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