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11-08-2009, 08:19 PM   #31
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QuoteOriginally posted by stevebrot Quote
Let's hear it for precise language!

Steve
I second that!

11-09-2009, 02:10 AM   #32
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so if I size a image to fit 8 x 10 page
then crop out what I want [that ends up being 3 x 3 inches]
and I enlarge that 3 x 3 crop up to the 8 x 10 size what do I call that??????
Alistair

Last edited by adwb; 03-31-2012 at 07:01 AM.
11-09-2009, 05:33 AM   #33
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QuoteOriginally posted by stevebrot Quote
"Crop of the image at capture resolution" ???


Arrrrgggg...
I like this...."cropped at capture resolution" sounds just about right...CACR, for short
11-09-2009, 05:40 AM   #34
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QuoteOriginally posted by Blue Quote
For artistic purposes you can make that argument. For technical or scientific purposes, this is not true. That is why micrographs often have a scale on them.

Even for scientific purposes, it still has validity. I'd say a 100% crop pretty much has no artistic merit but entirely for pixel peeping purposes. It definitely doesn't show the entire information, but very relevant information like what that part of the image looks like for pixel peeping at the pixel level.

Edit: As far as downsized images goes, it is still the entire image where a crop is not.

True, but they serve different purposes. If one wants to show the entire image and the file be not too large, then downsizing makes sense. However if I want to show a pixel level image and want the file size to be small, then a crop at original resolution is more appropriate. If the file size itself is irrelevant then the original downsized, uncropped image will give all information in it's entirety (RAW file).

...................

11-09-2009, 06:27 AM   #35
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QuoteOriginally posted by newarts Quote
You may be a little disappointed in your desire to "see what effect this has on distance to the subject". When the main lens is focused at infinity the working distance (distance from the lens to the subject) it is simply the close-up lens' focal length, which in case of the Raynox 150 is about 8.2".

With the Raynox 150, you'll have a working distance of 8.2" minus a little due to in-out motion of the main lens when you turn the focusing ring for any focal length primary lens.

That is, the Raynox 150's maximum working distance is 8.2". Period. If you add a teleconverter to the front of the stack the working distance will still be about 8.2".
"EDIT" what varies as you change the primary lens is the magnification, not the distance to the subject.

All that said, 8.2" is a reasonable working distance; about what you'd get with a 100mm macro lens at 1:1 magnification.
Newarts, thank you the 8.2" info is very interesting, so, at infinity with a prime I will have to crop and enlarge if the object is too small, conversely if the object is to large I will have to move the camera back?
So if I live with the oft reported poor IQ of a zoom the camera will not need to be moved as the zoom can be utilised?
BTW what is the distance for the Raynox 250?
Alistair
11-09-2009, 07:03 AM   #36
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QuoteOriginally posted by adwb Quote
Newarts, thank you the 8.2" info is very interesting, so, at infinity with a prime I will have to crop and enlarge if the object is too small, conversely if the object is to large I will have to move the camera back?
You cannot move the camera back and maintain focus; 8.2" is the maximum distance from Raynox 150 to subject.

QuoteQuote:
So if I live with the oft reported poor IQ of a zoom the camera will not need to be moved as the zoom can be utilised?
BTW what is the distance for the Raynox 250?
Alistair
Correct. The combination of a long zoom (like 50-200, 70-300, etc.) with a Raynox 150 is very convenient. The lens stays fixed in space 8.2" from the subject, while the magnification is changed by zooming.

The image quality may not be bad even with a mediocre zoom lens; you'll be using only the center part of the lens at small apertures, where the lens should be at its best.

The Raynox 250's focal length is 125mm, about 5". The 250's increased strength & decreased working distance makes it a little more difficult to use; for example the decreased working distance makes getting light to the subject more difficult - especially the on-board flash.

If you've a long zoom or selection of long lenses I recommend the 150.

Dave in Iowa

PS how about 100% crop = "displayed at capture resolution" or "one display pixel per sensor pixel"?

Last edited by newarts; 11-09-2009 at 12:27 PM.
11-09-2009, 11:52 AM   #37
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QuoteOriginally posted by adwb Quote
I suspect this has been covered many time so please point me to the thread but,

I wonder in the prime range of lenses available [any make] which would give the best IQ for taking images with a view to heavy cropping /enlargement??

my reasoning is the a "dedicated micro lens" is silly money. but given what you can achieve with top class prime and the 10-14mp cameras we now use , if a image has a nice low ISO and you are lucky enough to get that perfect in focus image with a decent DOF you can enlarge way past the magic macro figure of 1:1 with little loss of IQ.

So given the proliferation of used k lenses that are available from various sources, what are the best of the IQ ones to look out for?
Not certain I agree with your rationale. Go buy a DA 35Ltd and be done with. As good for general purpose as for macro. Rather exeptional actually for a "Macro" lens.
11-09-2009, 12:03 PM   #38
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QuoteOriginally posted by adwb Quote
BTW what is the distance for the Raynox 250?
Alistair
The Raynox 250 has a +8 diopter.
1/8 = 0.125 meters (4.9") working distance with host lens at infinity
To expand on Dave's comments above about the DCR-150. The 8.2" working distance is nice, but you will need a zoom with at least 210mm focal length to get 1:1. You may be able to get 1:1 with a shorter lens with focus at other than infinity, but the working distance will be less.

You might want to browse through this related thread:
https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/79076-raynox-h...40-helios.html
There a several comments where the details of calculating working distance and magnification ratios are touched on.

Steve


Last edited by stevebrot; 11-09-2009 at 12:12 PM.
11-09-2009, 05:30 PM   #39
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QuoteOriginally posted by pcarfan Quote
...................
QuoteOriginally posted by adwb Quote
so if I size a image to fit 8 x 10 page
then crop out what I want [that ends up being 3 x 3 inches]
and I enlarge that 3 x 3 crop up to the 8 x 10 size what do I call that??????
Alistair
I'd call it a lady beetle.
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