How to down size 34mp to 12mp


New Member
Apr 10, 2012
i saw image comparison of D3s and d800 and those d800 pictures were down sized to 12mp.
is there a proper way to resize these picture in photoshop to avoid much data lost or does the "Image" -> "Image Size" will do?

one eye jack

Senior Member
Jun 11, 2011
Nondestructive Editing
When you make edits to the image background layer, such as cropping
the image or changing the lighting, you change the pixels themselves.
Even though the changes may enhance the image, changing the pixels
is called destructive editing. Once again, I strongly recommend
working in a copy of an image so that you can always return to the
original if you decide to take a different creative path. Even when
you’re working with a copy, though, it’s convenient to retain
flexibility. You can take advantage of several features that let you
make nondestructive edits—that is, edits you can revisit, remove, and
modify any time you want to.

Adjustment layers, for example, let you make adjustments to tonal
levels,exposure, and other aspects of the image without affecting the
original pixels. Instead, the changes are made on a separate layer
that overlays the original. You can easily return to the adjustment
layer to modify the settings and change the way it affects the image.

You can even hide or delete the adjustment layer if you decide not to
use the changes. The easiest way to add adjustment layers is by using
the Adjustments panel.

Choose Window > Adjustments to open it.
When you click an adjustment icon, the Adjustments panel changes to
display the options for that adjustment layer. To add another

adjustment layer, click the Return to Adjustment List button at the
bottom of the panel.

tip By default, adjustment layers affect all the layers below them.
However, you can limit the adjustment layer—or any other layer—to
affect only the layer directly beneath it by creating a clipping mask.

Make sure the adjustment layer is directly above the layer you want to
affect. Then, select the adjustment layer, and click the Clip To Layer
icon (third from the left) at the bottom of the Adjustments panel.

(Alternatively, choose Create Clipping Mask from the Layers panel
menu.) The adjustment layer is indented with a small arrow next to it,
and the name of the layer it affects is underlined.

Likewise, Smart Filters make changes to the image without modifying
the pixels themselves. As with adjustment layers, you can make changes
to them at any time, even turning them off if you don’t want to use them
anymore. Smart Filters work only with Smart Objects, so in order to use
them, you need to first convert a layer to a Smart Object. Turn to

Chapter 7
to learn more about Smart Filters.
Any edits you make in Camera Raw are also nondestructive. Instead of
altering the image itself, Camera Raw writes the changes as metadata
that it attaches as a “sidecar” XML file, which travels with the
image. You can return to Camera Raw to revise or remove the edits you made at any
time. See Chapter 5 to learn about working in Camera Raw.

tip You can also use layer styles (described in Chapter 7) and masks
(described in the next section) to edit nondestructively.
Source: Photoshop CS5 Pocket guide page32.


Senior Member
May 16, 2005
Source: Photoshop CS5 Pocket guide page32.
I don't think any of that answered the TS's question... which was about resizing an image... :)

i saw image comparison of D3s and d800 and those d800 pictures were down sized to 12mp.
is there a proper way to resize these picture in photoshop to avoid much data lost or does the "Image" -> "Image Size" will do?
resizing in Photoshop in this sort of case is typically done via the "Image Size" interface as you had suggested... one thing to add is that in the "Image Size" interface, at the bottom of the window, there is the option "Resize Image"... for resizing smaller it is usually best to use the "Bicubic Sharper" option, and for resizing bigger it is usually best to use the "Bicubic Smoother" option... if you want to know the difference, read on... if not, just take this as reasonable advice :)

the difference between "Bicubic", "Bicubic Sharper", and "Bicubic Smoother" lies in what Photoshop does to the image after the main resizing operation... let's just take "Bicubic" to be the plain variety (if you are interested, you can read about "Bicubic" vs "Bilinear" here)... the thing about resizing is that detail in the image is either thrown out in downsizing, or invented when upsizing, and this has implications on the sharpness of an image...

in downsizing, detail is thrown out and the size of the image is reduced... the visible amount of detail is reduced in line with the reduction of the image size... but even in this sort of operation, a certain amount of "softness" (or maybe better described as uncertainty) is introduced due to the nature of "guessing" what to remove... so Adobe thought to add a "Bicubic Sharper" option, where the resizing operation adds a bit of sharpening to produce a sharper image than just by the "Bicubic" option...

in upsizing, pixels are added by Photoshop, which makes a guess of what the added pixels should look like... as this is just guessing, no new real detail is available... as Photoshop is just guessing from what is already there, it tries to "expand" the original detail, resulting in a softening of the image... the "Bicubic Smoother" option is supposed to allow this upsizing process to produce smoother results in upsizing, which is supposed to produce a better looking upsized image... it is then left to the user to sharpen the resulting image to taste...

the plain variety "Bicubic" is an in-between option... it neither sharpens the image in downsizing, or biases an image smoother in upsizing... it is for when the other options produce an image that is too sharp in downsizing, or too smooth in upsizing (unlikely as this case might be), so the user may make further decisions on sharpness from a more neutral basis after the resizing operation...

but as in many things, YMMV :)

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