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milesy · 11-05-2010, 03:19 AM

hi - back to this again......

having given a bit more thought i think the k-7 photo above was a bit unfair - when i rechecked the shutter speed was only 1/10 of a second - so its not really a fair shot.

So what next....i thought i would compare using a flash so as to even up the field a bit and i thought i would compare the 28-300 (the one i was complaining about) and my 70-210 (sigma also).

here are the two shots.

and

ok first thing is if you lookt it is clear that one shot is sharper than the other.....also it is clear from these two shots taken from the exact same postion that the focal length of one is greater than the other.

Ok here is the real kicker - the shot where the DVD box is larger is the 70-210mm NOT The 28-300 (both used wide open at max zoom)

WHAT THE??? does this make any sense at all

milesy · 11-05-2010, 06:58 PM

anyone?

**dadipentak** · 11-06-2010, 04:40 AM

Originally posted by milesy

anyone?

I'm stumped.

JeffJS · 11-06-2010, 11:56 AM

Sigma Zoom lens - 28 mm - 300 mm - F/3.5-6.3 - Pentax K

Is this your Sigma 28-300? Optimized for Digital (APS-C)?

milesy · 11-06-2010, 01:30 PM

JeffJS - well i didnt think it was - when you look at the EXIF data it reports EFL 450 but clearly something is amiss

JeffJS · 11-06-2010, 02:15 PM

The reason I was asking was, I was wondering if there is something about the 'optimized for digital' that gives us a different field of view. I once had a bellows and wanted to digitize slides with it. When I put a Film type 50mm lens on the bellows no matter what settings I used, I could not get past the APS-C crop to get a full copy of the slides. When I put my DA 50-200 on the bellows and set it to about 60mm not only could I get the full slide image but also part of the cardboard slide mount frame as well.

After writing however, I went out and tested the theory again, comparing my FA*85 to my DA*50-135 at 85mm, and the photos taken from the same distance, are identical. That is, no apparent change in crop. So, I don't know what's going on with your photos either.

Pigeon · 11-06-2010, 10:01 PM

Internal focusing lens does not provide full focus distance when focused on close target. Never thought the effect such strong.

11-06-2010, 01:30 PM	#20
milesy Veteran Member Join Date: Jan 2009 Location: Melbourne Photos: Gallery Posts: 379 Original Poster	JeffJS - well i didnt think it was - when you look at the EXIF data it reports EFL 450 but clearly something is amiss Last edited by milesy; 11-06-2010 at 01:43 PM. Reason: ECIF > ECIF

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11-05-2010, 03:19 AM	#16
milesy Veteran Member Join Date: Jan 2009 Location: Melbourne Photos: Gallery Posts: 379 Original Poster	hi - back to this again...... having given a bit more thought i think the k-7 photo above was a bit unfair - when i rechecked the shutter speed was only 1/10 of a second - so its not really a fair shot. So what next....i thought i would compare using a flash so as to even up the field a bit and i thought i would compare the 28-300 (the one i was complaining about) and my 70-210 (sigma also). here are the two shots. and ok first thing is if you lookt it is clear that one shot is sharper than the other.....also it is clear from these two shots taken from the exact same postion that the focal length of one is greater than the other. Ok here is the real kicker - the shot where the DVD box is larger is the 70-210mm NOT The 28-300 (both used wide open at max zoom) WHAT THE??? does this make any sense at all

11-05-2010, 06:58 PM	#17
milesy Veteran Member Join Date: Jan 2009 Location: Melbourne Photos: Gallery Posts: 379 Original Poster	anyone?

11-06-2010, 04:40 AM	#18
dadipentak Site Supporter Join Date: Jul 2008 Location: Baltimore, Maryland Photos: Gallery Posts: 11,590	Originally posted by milesy anyone? I'm stumped.

11-06-2010, 11:56 AM	#19
JeffJS Inactive Account Join Date: Aug 2008 Location: Michigan, USA Photos: Gallery \| Albums Posts: 7,484	Sigma Zoom lens - 28 mm - 300 mm - F/3.5-6.3 - Pentax K Is this your Sigma 28-300? Optimized for Digital (APS-C)?

11-06-2010, 02:15 PM	#21
JeffJS Inactive Account Join Date: Aug 2008 Location: Michigan, USA Photos: Gallery \| Albums Posts: 7,484	The reason I was asking was, I was wondering if there is something about the 'optimized for digital' that gives us a different field of view. I once had a bellows and wanted to digitize slides with it. When I put a Film type 50mm lens on the bellows no matter what settings I used, I could not get past the APS-C crop to get a full copy of the slides. When I put my DA 50-200 on the bellows and set it to about 60mm not only could I get the full slide image but also part of the cardboard slide mount frame as well. After writing however, I went out and tested the theory again, comparing my FA85 to my DA50-135 at 85mm, and the photos taken from the same distance, are identical. That is, no apparent change in crop. So, I don't know what's going on with your photos either.

11-06-2010, 10:01 PM	#22
Pigeon Junior Member Join Date: May 2009 Location: Chicago Photos: Albums Posts: 35	Internal focusing lens does not provide full focus distance when focused on close target. Never thought the effect such strong.

300mm Lens

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