Author Topic: Spirit level for A700?  (Read 7878 times)

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Offline chappo1

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Re: Spirit level for A700?
« Reply #15 on: September 11, 2013, 11:30:14 PM »
I do not worry about the theory but I have never noticed any problems either on screen or when printed (up to A4) when I have adjusted horizon or verticals.
I do not print many A3 but on the couple I have done, I have not seen a problem either....john
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Offline peterboulton

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Re: Spirit level for A700?
« Reply #16 on: September 12, 2013, 12:17:03 PM »
Subjectively I fully accept that it may be impossible to see the difference between an interpolated tilted adjustment and the original photo.  I don't know.

However, I still don't see how adjustment isn't lossy. Please see this page I just put up, which shows the result of horizon adjustment on a simple image: http://www.dataper.demon.co.uk/horizonadjustment/.

I think this 'proves' interpolation has to take place.

In order to understand whether the interpolation is noticeable to the human eye and when I have more time I may try using the software adjustment twice on the same image - i.e. tilt it one way and then use the software to tilt it back by exactly the reverse amount.  The original image and the doubly-tilted image should look identical.  Anyone fancy the same exercise?

Pete

Offline Faldrax

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Re: Spirit level for A700?
« Reply #17 on: September 12, 2013, 12:58:34 PM »
In order to understand whether the interpolation is noticeable to the human eye and when I have more time I may try using the software adjustment twice on the same image - i.e. tilt it one way and then use the software to tilt it back by exactly the reverse amount.  The original image and the doubly-tilted image should look identical.  Anyone fancy the same exercise?

Note that you need to be careful how this is done.
If, for example, you do the exercise in Lightroom on a RAW file, the result will (or should) be 100% lossless, as the two reversals will cancel and LR will do nothing.
If, on the other hand, you do this in PSE with a JPeg, you would get a loss from JPeg compression if you saved after each rotate, independently of the rotation effect.
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Offline Frank [aka Wires]

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Re: Spirit level for A700?
« Reply #18 on: September 12, 2013, 01:47:43 PM »
Hi Pete

Others with more knowledge than I would have to answer your question. I checked your link and studied your images and I am not sure if you are taking in to account the way monitor screens interpret/present the information they are displaying to the viewer. I apologies if that come across wrong and is oversimplifying the conundrum. :?

If you zoom in on any diagonal line (or circular line) you will always see a 'staggered' line - as in your zoomed angles image - because the screens can not replicate a line as you or I would draw it with a pencil or pen. That is because of the PPI resolution of the screen - to me anyway - made up of squares, that's how I interpret and understand it. :?

I've always understood monitor screens to be made up of X number of squares depending on the resolution it is set at. The more you zoom in the more 'pixilated' the image becomes and is seen on diagonal lines.

About 18 years ago I had to edit an image scanned from a photograph - taken of a line drawing in a book. The image was of a bird in flight around a bush/tree. I only wanted the image of the bird so had to remove all the rest around it. I had to zoom in considerably to get as fine a detail as I could and had all these jagged edges for the bird; wings, tail, head... made up of squares. I did not have to rotate any part of the original 'digital' image.

Maybe I'm misunderstanding you and the question of an image becoming 'lossy' if/when you do any rotation at an angle but I can only express what my experience on 'manipulation' of images has shown me. So I apologies again if I've misunderstood the question you want an answer to :-[
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Offline peterboulton

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Re: Spirit level for A700?
« Reply #19 on: September 12, 2013, 01:50:26 PM »
Note that you need to be careful how this is done.
If, for example, you do the exercise in Lightroom on a RAW file, the result will (or should) be 100% lossless, as the two reversals will cancel and LR will do nothing.
If, on the other hand, you do this in PSE with a JPeg, you would get a loss from JPeg compression if you saved after each rotate, independently of the rotation effect.

Yes, absolutely.  As you say, some software remembers the steps taken and cumulatively applies them to the image in memory, allowing them to be 100% reversed.  The 'fair' test is to ensure the image file is saved in its tilted format first and then worked on as, effectively, a different image.

Offline peterboulton

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Re: Spirit level for A700?
« Reply #20 on: September 12, 2013, 03:44:08 PM »
Hi Pete

Others with more knowledge than I would have to answer your question. I checked your link and studied your images and I am not sure if you are taking in to account the way monitor screens interpret/present the information they are displaying to the viewer. I apologies if that come across wrong and is oversimplifying the conundrum. :?

If you zoom in on any diagonal line (or circular line) you will always see a 'staggered' line - as in your zoomed angles image - because the screens can not replicate a line as you or I would draw it with a pencil or pen. That is because of the PPI resolution of the screen - to me anyway - made up of squares, that's how I interpret and understand it. :?

....

Hi Frank,

Yes, point 100% taken.  I agree that pixels are represented as square dots on the screen and therefore a diagonal line will always be jagged.  However, would you accept that my tilted images shows much more jaggedness than can be explained by this?  That it shows quite a lot of anti-aliasing?

I just updated the page at http://www.dataper.demon.co.uk/horizonadjustment/ as I tried applying the exact reverse amount of tilt to the saved tilted image in RawTherapee.  To me I 'see' lost definition in addition to the (unavoidable) cropped borders as a result of the tilt / reverse-tilt.

Methinks I am becoming abnormally fascinated by this subject!  I am certainly questioning my original thought process on the subject and am slightly less certain about lossy/non-lossy than I started.

Happily, at the end of the day my musings are pretty unimportant as you wouldn't deliberately take an off-level photo (except as a 'statement') and if you did then using software to correct it would give a more pleasing overall result, even if some small amount of definition is lost, than not resolving the incorrect horizon.

The end!  :-)

Pete

Offline retoohs

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Re: Spirit level for A700?
« Reply #21 on: September 13, 2013, 11:58:28 PM »
Great thread Pete. I've done a little research since you started this thread and the general concensus is tilting an image to an arbitrary angle is destructive to some pixels though not everything I've read is in agreement. As I often straighten horizons I'm most interested in finding out the truth about it. Never was a problem with film where there was no loss tilting a negative during printing :-). Back to your original question I still think it is technique and a level won't solve it totally. I have an awful habit of left hand down even though I carefully composed it straight. Now I'm aware of it most times I'm able to get the horizon where I want it. As I said earlier where I have a tricky horizon I often will bracket shots where I alter the horizon slightly and have had good success doing so. Anyway enjoying the thread and look forward to learning more about this.

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Offline peterboulton

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Re: Spirit level for A700?
« Reply #22 on: September 14, 2013, 10:19:03 AM »
Great thread Pete. I've done a little research since you started this thread and the general concensus is tilting an image to an arbitrary angle is destructive to some pixels though not everything I've read is in agreement. As I often straighten horizons I'm most interested in finding out the truth about it. Never was a problem with film where there was no loss tilting a negative during printing :-). Back to your original question I still think it is technique and a level won't solve it totally. I have an awful habit of left hand down even though I carefully composed it straight. Now I'm aware of it most times I'm able to get the horizon where I want it. As I said earlier where I have a tricky horizon I often will bracket shots where I alter the horizon slightly and have had good success doing so. Anyway enjoying the thread and look forward to learning more about this.

Alan

Hi Alan,

I think your posting makes a great overall summary.  Yes, horizon correction is almost certainly destructive in terms of some pixels but in reality the destruction or lack of destruction is in the eye of the beholder.

Having the option to correct in software is great because it can rescue an otherwise great image, which would otherwise be unlivable with.

As I prefer to spend time taking photos and aspire to spending as little time as possible in the software I now have a renewed determination to shoot level to start with and to analyse verticals / horizontals in the viewfinder before I take the photo!

Pete

Offline dynax dingbat

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Re: Spirit level for A700?
« Reply #23 on: September 29, 2013, 09:28:46 PM »
I had the same problem with my A700, and in fact all my Alpha cameras.
I found that it was caused when I pressed the shutter, I loosed the grip of my right hand and the body moved, nearly all my tilting was one way! Using a vertical battery grip improved this markedly. (My VG-C70AM is now languishing as an agency sale, but nobody wants to buy it.)
In fact I could even shoot one handed with the grip but of course with no live view you take pot luck anyway regarding horizontals.
Graham

Offline peterboulton

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Re: Spirit level for A700?
« Reply #24 on: October 02, 2013, 10:48:44 AM »
I had the same problem with my A700, and in fact all my Alpha cameras.
I found that it was caused when I pressed the shutter, I loosed the grip of my right hand and the body moved, nearly all my tilting was one way! ..
Graham

Hi Graham,

Yes, that's a fair point and I could have a similar affliction!  I have no experience of other DSLR brands - surely the shutter button is somewhere off-centre on all DSLRs though?  Is the Sony button particularly stiff?

When depressing the shutter I always try to do it as softly as possible but I definitely wouldn't rule out the possibility of slightly tilting it on occasions.

Since starting this thread I've 'upgraded' from Picasa to Lightroom 5 for my digitial images and maybe horizontal adjustment, if needed, is no more 'evil' than any other digital dark room adjustment and maybe I was being a bit 'anal' in complaining about 'lossy' straightening!

I continue to strive for level horizons, but with less anxiety when I'm slightly 'off' these days!

Pete

Offline rebeccah

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Re: Spirit level for A700?
« Reply #25 on: October 09, 2013, 12:11:06 PM »
Hi John

Quick query:  why are you using "Correct Camera Distortion" to see if the horizon is straight, then cancelling before rotating using Image > Rotation > Degrees? 

I only have PSE7 (which may be very different to PSE11), but if I want to tweak the horizon, (which I often get wrong, though I'm a bit better now there's the spirit level in the viewfinder with the A77) I then change the angle within the "Correct Camera Distortion" control panel which shows to the right of my image.  You can put numbers in there until you are happy with it.  Is that not easier, or have I missed something myself, I'm no expert when it comes to PS.

Thanks

Rebecca

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Offline Gordon McGeachie

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Re: Spirit level for A700?
« Reply #26 on: October 10, 2013, 09:00:50 PM »
if I get a wonky horizon, i use the `free rotate` function on paintshop pro x.

is this not available on the more expensive programs then...........................?


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Offline AScot

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Re: Spirit level for A700?
« Reply #27 on: October 10, 2013, 10:15:04 PM »
Hey Gordon, is PSE7 or PSE11 not cheaper than paintshop pro x? They are in North America.

In Photoshop you use the ruler tool, click Image >Image rotation> Arbitrary.... It then puts in the degrees of rotation Automatically.
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Offline rebeccah

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Re: Spirit level for A700?
« Reply #28 on: October 22, 2013, 10:29:59 AM »
Hi John

Was using PSE7 the other day having not used it for a while and remembered the Straighten tool, which I had completely forgotten about.  In PSE7 the symbol is 2 overlapping rectangles.  Once you've clicked on tool, you draw a line along something you think should be horizontal and then it rotates it accordingly.  You can also use it to check verticals by holding the Ctrl key whilst drawing your line, which I think is more reliable than checking horizontals if you are taking pictures with the camera looking directly forwards rather than up or down, if you see what I mean,

Hope this is useful

Rebecca
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Offline Gordon McGeachie

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Re: Spirit level for A700?
« Reply #29 on: November 17, 2013, 12:32:09 PM »
Hey Gordon, is PSE7 or PSE11 not cheaper than paintshop pro x? They are in North America.

In Photoshop you use the ruler tool, click Image >Image rotation> Arbitrary.... It then puts in the degrees of rotation Automatically.

missed this one somehow..................

I know have paintshop pro x2 on my new tower, so no need to pay out for elements now
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