How do I tell if the shot is in focus?

[SheffieldPhotos]

I know this may seem a silly question but after using a D-SLR (D80) for 12 months I still struggle with this point. After taking the shot (nowadays exclusively in RAW) I zoom into the display to review the shot and check for sharpness and other imperfections.
However, when I look I am never quite sure when it is in sharp focus due to the fact that the image is unsharpened. Also it is possible to zoom in to a very high magnification whereby the image is clearly pixellated.
So what advice do you have? Is there a way of reviewing the image at 100% like you can within Photoshop? After all, that's what matters.

[beejaybee]

I'm not sure how it works with the camera you have but with the Canons the "magnified review" is of limited value because all you're doing is blowing up a rather poor JPEG thumbnail of the image. Nothing to do with the hi res raw image stored on the card.

My advice is to trust a combination of the autofocus mechanism & what you can see in the viewfinder at the instant you press the shutter release. Then ignore the review screen. I used to be able to get reasonably well exposed, sharp images (almost) every time on film, without the "benefit" of the review screen, and working the same way with digital works for me - faster & more convenient than messing with the review screen at shooting time.

The benefit of digital is that the occasional duffers don't cost film ... just get a decent sized flash card & delete the non-keepers after uploading to the computer, reviewing at a decent resolution and with a calibrated screen.

[Gordon_McGeachie]

I suppose the resolution of the screen would be something to do with it.

Is it 230,000 or 920,000 pixels.

[beejaybee]

I suppose the resolution of the screen would be something to do with it.

Is it 230,000 or 920,000 pixels.

Indeed, but to get a decent impression of the sharpness of the image it needs to have at least the same number of pixels.... 2x oversampling is better, implying that a camera with a 20MP sensor should have an 80MP review screen. That's going to be inconveniently large, and the power consumption would be horrific.

[Gordon_McGeachie]

I suppose the resolution of the screen would be something to do with it.

Is it 230,000 or 920,000 pixels.

Indeed, but to get a decent impression of the sharpness of the image it needs to have at least the same number of pixels.... 2x oversampling is better, implying that a camera with a 20MP sensor should have an 80MP review screen. That's going to be inconveniently large, and the power consumption would be horrific.

My Sony A700 is 12.2 mp but has a 921,000 pixel rear screen and that is superbly clear, I was not referring to the MP of the camera in question.

[SheffieldPhotos]

Thanks for the reply but maybe I should have been more specific. I have no real problem judging depth-of-field focus, more a case of hand-held shots. I am never quite sure if I have got camera shake from a relatively slow exposure e.g. 30th at 50mm or 15th at 130mm with a monopod. That is when I use the LCD to try and judge the focus.

Or is it just a case of developing some hard-and fast rules like the classic 50th at 50mm (in 35mm film)?

[john_g]

Strange, because I have no problem knowing whether the images are sharp on my Samsung GX-10, and that must have much the same preview capabilities as a D80... 2.5" LCD with 210,000 pixels and magnification up to x20. I find this x20 magnification to be perfect for judging images - no individual pixels are visible, but any blur or unsharpness is easily seen. I need glasses for reading nowadays, but can use my camera without them.

[Burgy]

Practice will help, I regulary delete images on the basis of the preview screen, though shrpness is not normally the problem, eyes shut or not looking at camera.

Camera shake is usually easy to identify, at least in my experience.

[Terrywoodenpic]

I don't think I can tell from looking at the screen.
However If you focused in the right place and held the camera steady and used fast enough shutter speed it will be sharp.
It is a confidence thing.....
I would say I rarely chuck out over sharpness, it is usually because I did not like the shot for other reasons, or the exposure could have been chosen differently.

[benji]

Open the file in Photoshop and zoom in at 100%. Look at the intended area of focus (at 100%).

[alanworland]

I understand that when reviewing a RAW shot on camera (40D) that you would be looking at a low quality jpeg that is embeded in the file, but if a high quality jpeg was saved AS WELL as the RAW file, which image would be viewed upon playback?

[Ben_Wearden]

I ususally know if the thing i wanted to be the Subject of the photo is sharp and crisp with no soft/blurred area's and the background has a slight blur to it.

[benji]

I think I kind of misunderstood your question.
You mean "sharpness when reviewing images on your DSLR screen", is that correct?

I find this way of assessing IQ virtually impossible, as the results are sooo far off what you would actually notice when reviewing images on your computer screen. I never use the camera screen to check sharpness, because I find it just doesn't work, even when zooming in as much as the camera screen allows.

I'd be tempted to say that there is no answer to that. Only to ensure I always bear in mind the fundamentals of image capture, i.e:
- shutter speed in relation to focal length when shooting handheld
- shutter speed in relation to subject movement
- use or not of image stabilisation facility, which have a slight impact onto what I can get away with when shooting handheld
- use a tripod whenever possible
- avoid light diffraction by using the widest aperture I can get away with to achieve the DOF I want (i.e.: don't stop down to f/32 if f/16 is enough)
- if possible, use hyperfocal distance focusing with high f-stops
- if focusing to infinity and DOF is not an issue (nor is shutter speed), don't use the widest aperture, but try and stop down by two stops (roughly).
- use decent quality filters (and lenses)
- get in as close as I can to my subject (this one really sound like a dumb one, but if you can stand close with a 35mm -as opposed to further back with a 85mm- the resolution of detail will be greater. I know, it impacts on the perspective as well, but sometimes you may not mind that, depending on how prepared you are to adapt to the focal length you're using)
- plus a few other things that I'm bound to have forgotten!

Also, quite importantly; I've had to establish how slow a shutter speed I can use when shooting handheld. Image-stabilisation and lack of experience can fool anybody into thinking they can shoot anything and everything handheld.

Once I've made sure of these, I don't have to worry about reviewing images on my screen to check for sharpness. I just check my histogram or the composition, but sharpness will be fine, no real need to worry about it.

Benji

[benji]

I understand that when reviewing a RAW shot on camera (40D) that you would be looking at a low quality jpeg that is embeded in the file, but if a high quality jpeg was saved AS WELL as the RAW file, which image would be viewed upon playback?

I'm not entirely sure whether shooting RAW only, or jpegs only (full size/hi-res), or RAW+jpegs combined would deliver a different quality of preview image when viewed on the preview screen.

Maybe if you shoot medium/small size jpegs only (as opposed to RAW or full size jpegs), then maybe that will impact negatively on preview image quality.

But I may be wrong. Somebody else may be able to chip in to confirm or correct the above.

Benji

[TimF]

Open the file in Photoshop and zoom in at 100%. Look at the intended area of focus (at 100%).

I'd say 50%. Nothing ever looks sharp at 100%. Indeed, doing so is akin to peering at a print from a few inches with a magnifying glass. Do you do that?

[Benchista]

I would agree. 100% is great for getting rid of dust marks etc, but not all that good for judging image quality in any way IMVHO.

[benji]

I would agree. 100% is great for getting rid of dust marks etc, but not all that good for judging image quality in any way IMVHO.

Each to their own.
Both are good, as long as you know what to look for.

Benji