dslr large format please help!

l21

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I am taking an image needed for a poster 30x40 inch, using canon 5d mk lll. I am shooting at night with 100 iso, 125 shutter and 2.8 aperture, RAW.

For lighting I have been using an epson projector (the kind to watch films on indoors, I wanted the rectangle projection on my subject as I want it to look as if there is a cinema screen out of shot) , as well as some lights from a cheap lighting kit from ebay and some spill from general garden lights.

I have the camera settings to take the image at 5760x3840, and on photoshop the image size originally is 19.2x10.8 inch - when i try to make it larger it becomes too heavily pixilated. There is enough light in the image (in terms of the way I want it to look), however could it be the quality of light making it so pixilated?

I don't want any more light in the image, but I don't know how to increase the quality which I really need to print large format.

I would be really really grateful for any suggestions!

Thank you xxx
 

480sparky

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"Quality" of light has no bearing on pixelating of an enlarged image. That's strictly a function of the number of pixels in the image.

A 22mp original should easily print 30x40. But that size of print is not intended to be viewed at 10".
 
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l21

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Thank you for your reply.
Do you know why it looks so pixilated when I try to enlarge it on image size or zoom in? Regardless of how it is intended to be viewed it should still be sharp?
Thanks
 

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5760 px divided by 19.2 inches = 300 pixels per inch (ppi).

To print 5760 px at 40 inches you need to change the ppi - 5760 / 40 inches = 143.5 ppi

At 143.5 ppi, even as close as 10 inches away, pixels will not be visible.
But if you print from a JPEG file you may see the boundaries of MMUs - Minimum Coded Units - which are a means JPEG uses to reduce the file size.
MMU's are 8x8 pixel, 8x16 pixel, or 16x16 pixels units (depending on what device made the JPEG) that are the smallest JPEG file units that can be edited.

If you use a print lab that will print from an 8-bit TIFF file there won'rt be any JPEG MMUs to worry about.
 
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l21

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Thank you all

So now I'm looking at it and I'm thinking maybe it just looks rubbish quality because it also looks out of focus, and am feeling a bit stupid. I have been using auto focus yet none of the image is really sharp, I originally put it down to image quality rather than bad technique.
$Screen Shot 2014-09-10 at 02.54.04.png

This is a screen shot of a small section at 30x40 resolution 300

If it is just my bad focusing, is there any advice on focusing in low light conditions that would help?

Many many thanks again
 
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l21

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I should explain I think i was viewing it larger than 30x40 in my original post which is why I thought it was just pixilated. However if I am using auto focus (which was directed at this spot in the image), even if the rest was out of focus I don't understand why this part is.
 

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Auto focus uses contrast to detect edges.
If there are few edges AF has trouble working well.
Understanding Camera Autofocus
Understanding Depth of Field in Photography

Many lenses opened to a wide (fast) aperture like f/2.8 cannot focus sharply (soft focus) because the light from the outer edge of the lens opening does not focus to the same point the center part of the lens focuses to.
To combat that many 'fast' lenses have to be stopped down a couple of stops. f/5.6 is a 2 stop smaller lens opening than f/2.8.
But if you make the lens aperture smaller less light gets in, and if you want to maintain the same exposure you have add exposure by using a higher ISO and/or a slower shutter speed.
In other words, you can add back 2 stops by adding 1 stop of ISO and 1 stop of shutter speed,

f/5.6, ISO 200, and !/250 delivers the same exposure as your f/2.8. ISO 100, and 1/125.

You may be asking yourself - WTF is a stop?

A Stop
A 'stop' is a doubling (2x) or a halving (0.5x) of the amount of light getting the image sensor/film. A stop is a fundamental photography concept.
A stop change in exposure can apply to the lens aperture, the shutter speed, the ISO, or all 3.

Since exposure is a triad of adjustments (shutter speed, ISO, lens aperture) you can change 1, 2 or all 3 of the triad settings.

If you want 1 more stop of exposure (brighter) you can adjust just one of the 3 by 1 more stop.
Or, you can change 2 of the 3 by 1/2 more stop each for a net gain of 1 stop of exposure.
Or, you can adjust all 3 by 1/3 more stop for a net gain of 1 stop of exposure.

You can also change the triad of settings and have no change in the exposure.
If you change 1 of the 3 settings by 1 stop more exposure and change a 2nd setting by 1 stop less exposure the net change is zero.
Suppose you subtracted a stop of shutter speed to help stop subject motion, you could add a stop of lens aperture to keep the exposure the same. However, adding a stop of aperture will also affect the total DoF by a small amount. So, if you don't want the DoF to change you would add a stop of ISO instead, however, adding a stop of ISO will increase by some amount the image noise in the photo.

Note: DSLR cameras are set by default to adjust the exposure settings in 1/3 stop increments.
Most DSLR cameras let you change that to 1/2 stop or 1 stop increments.
However, the advantage of 1/3 stop step increments is more precise control of exposure.
 
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l21

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Thanks a lot Keith
I did go back and try after my last post to use a smaller aperture and longer shutter speed on a tripod, but the sharpness has not improved. I have directed the focus on various areas and tried manual focusing as well but nothings really working.
I don't understand what the problem is! But only have use of this camera for 1 more day so really need to get this sorted.
The lens is EF16-35mm f/2.8L II which is meant to be good in low light as well so I really dont know whats going on
 
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l21

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just for reference this is how it looks with 1/30 sec; f/5.6; ISO 125

$Screen Shot 2014-09-10 at 04.39.37.png

am I being unrealistic in my expectations? I don't know what else to try
 

chuasam

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Use a tripod and an aperture like f/8


Sent from my iPad using Tapatalk
 

Holejee

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It appears to have a blue cast, as well. Not sure if that was your intent.
 

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