Lens Calibration?

You mean AF micro-adjustment?

Not usually, no. I think it's more of a marketing feature, and it takes the heat out of manufacturer's service departments who get sent lenses that are claimed to be out by obsessive pixel peepers, but are actually within tolerance.

I recently got micro adjust on a 5D2 and of course spent hours checking everything. In the end, I gave one of my three lenses +6 which is a shift of about 3mm in 3m. There's no way you can focus that accurately in real shooting. But of course, it had to be done ;)

It's actually very hard to do a proper test and reset. You must do it at a sensible distance and not really close with one of those test targets you can download. You are almost bound to find errors with those, as all lenses are a compromise setting than varies with focal length and distance. They are built to a tolerance.

TBH I was pretty amazed at how accurate, and how consistently accurate, the AF was/is even in difficult conditions.
 
Thanks Hoppy

I think I may be a "pixel peeper" ;)

I also think I maybe trying to get a crystal picture of small birds with my 70-300 Canon IS USM. When possibly most of my shots are getting the subject only taking up 10/20% of the shot.

When I've posted "straight from camera" shots which are only cropped, I am being told to sharpen, then too much sharpening :bang:

When we talk cropping %, are we talking the amount of original frame you are removing? :shrug:
 
Mickwreay said:
Thanks Hoppy

I think I may be a "pixel peeper" ;)

I also think I maybe trying to get a crystal picture of small birds with my 70-300 Canon IS USM. When possibly most of my shots are getting the subject only taking up 10/20% of the shot.

When I've posted "straight from camera" shots which are only cropped, I am being told to sharpen, then too much sharpening :bang:

When we talk cropping %, are we talking the amount of original frame you are removing? :shrug:
Click to expand...

We're all pixel peepers! Just don't be too worried about what you see. Everything looks woolly at 100%.

But I'm pretty sure your problem is cropping. Basically, don't. It is death to image quality. First rule for image quality is to fill the frame with the subject, end of story. If you do that, and focus carefully (centre point, on the eyes) with a shake and blurr free shutter speed (that lens, IS on, 1/250sec or shorter) you will not be complaining about about sharpness or focus issues.

With small garden birds, that means a distance of less than 3m. If you can't get closer than that, you'll struggle. Birding is very difficult, it's one of the most testing subjects. You need very good technique, excellent field craft, and TBH, a massive lens is a big help.

On the focus micro-adjust thing, it's easy enough to check but you must be extremely careful, test a range of distances and focal lengths and if there's any change work out the best average. Just don't do it at a silly close distance or any corrections will throw the lens out at normal distance shooting range.

The closest we've got to an official guide to how it should be done is on this link form Chuck Westfall of Canon USA, second question down http://www.digitaljournalist.org/issue0812/tech-tips.html He says minimum distance of 50x focal length but you'll find that's almost impossible to do in a meaningful way with your lens at 300mm. I would say don't go closer than 5m, which is not an unrealistic distance, but double-check infinity focus afterwards if you make any changes.
 
HoppyUK said:
The closest we've got to an official guide to how it should be done is on this link form Chuck Westfall of Canon USA, second question down http://www.digitaljournalist.org/issue0812/tech-tips.html He says minimum distance of 50x focal length but you'll find that's almost impossible to do in a meaningful way with your lens at 300mm. I would say don't go closer than 5m, which is not an unrealistic distance, but double-check infinity focus afterwards if you make any changes.
Click to expand...

Why is it unrealistic distance? 50 * 300mm is 15000mm = 49 feet and 2.55 inches
look at it like this 300mm is one foot so 50 feet?
 
After checking 6 of my lenses, only 1 needed slight adjustment, and the difference its made is barely noticeable if at all. Its easy to become obsessed with what we see as a perect setting when in most cases it makes no difference in practice.
A useful site I found was this one, its mainly for Canon users but the principle could maybe apply for other makes too.

EDIT: I checked the lenses on 2 cameras, the one that needed adjustment needed the same adjustment on both cameras.
 
Chaz Photos said:
Why is it unrealistic distance? 50 * 300mm is 15000mm = 49 feet and 2.55 inches
look at it like this 300mm is one foot so 50 feet?
Click to expand...

The problem is depth of field. At 15m distance, with a 300mm lens at f/5.6 on a 50D the OP has 53cm of DoF. Picking the sweet spot out of that, reliably - well frankly you can't do it.

You need to move closer in order to force more differential in the DoF, but then you run into the danger of moving unrealistically close and ruining the whole thing.

I think Trev makes a good point above. Unless something is clearly wrong with your focus calibration, and you have noticed a consistent variation in normal picture taking, ie front-focusing by a similar amount, then leave it alone. If you go looking for problems by pushing things to unrealistic extremes, there's a good chance you will find some.
 
Chaz Photos said:
Can you re-word this question not sure what your asking
Click to expand...

Sorry,

If I have a bird being 2cm in a picture of 10cm then it is 20% of the picture, if I then crop it to make it around 50% of the picture then what percentage cropping is this?

Better?

Mick
 
Mickwreay said:
Sorry,

If I have a bird being 2cm in a picture of 10cm then it is 20% of the picture, if I then crop it to make it around 50% of the picture then what percentage cropping is this?

Better?

Mick
Click to expand...

You're looking at linear, not area.

Taking your 20% of linear width figure, that translates to an area of the sensor about 4.4 x 3mm, which is 13.2sq mm out of a total 332sq mm. That's 4%, an area about the size of a child's little finger nail.

You are throwing away 96% of the lens/sensor potential :eek: Cropping is death.
 
HoppyUK said:
You're looking at linear, not area.

Taking your 20% of linear width figure, that translates to an area of the sensor about 4.4 x 3mm, which is 13.2sq mm out of a total 332sq mm. That's 4%, an area about the size of a child's little finger nail.

You are throwing away 96% of the lens/sensor potential :eek: Cropping is death.
Click to expand...

Starting to become clear :thinking:

In basic terms, fill the frame as much as you can & thats what the lens is for?

the better the body & lens are ,the better the pic "should" be?

Mick
 
Mickwreay said:
Starting to become clear :thinking:

In basic terms, fill the frame as much as you can & thats what the lens is for?

the better the body & lens are ,the better the pic "should" be?

Mick
Click to expand...

Well, almost. But not fill the frame as much as you can, just FILL THE FRAME.

It is far and away the best, easiest and cheapest way of getting good image quality.

If for example you crop 50% of the linear width, you've just thrown away 75% of the usable image area. There is no lens, camera, sensor or anything else on earth that can restore that level of loss.

Birders only crop their images when they have run out of all other options, and even then as little as possible. The rule with birding is pretty much get the longest lens you possibly can, then get as close as you get. You will never be too close.

Naturally enough, that isn't as easy as it sounds but you can still make some great bird images by making more of the surroundings and creating an 'environmental' portrait. If you check out the images in the bird forum here, you will see lots of superb shots where the bird is actually quite small in the frame :)
 
I've found that if I can get about 2000 pixels on the longer side which is an approximate quarter crop by area then that's good enough for a sharp A4 print. This wren was shot probably about 15 feet away at 400mm focal length and iso 800. It's resized down from 1238x860, but the 100% crop looks ok after a bit of sharpening. After cropping but before resizing the image size was 1.1MP, about a 90% crop by area. It'd probably look sharp on a 5x7" print.
As for the comment, "you'll never be too close", this is not strictly true, although most of the time you're going to have to crop. However, woodland birds in winter can get very tolerant when food is offered and you can get very close indeed, so much so that with the available light restricting how far you can stop down, you can get a situation where you focus on the bird's eye and the beak is unsharp. In such situations it will help to leave a little wriggle room and crop to frame the shot afterwards. But you do need good lenses, and if you have the luxury of AF micro-adjustment ( I don't, unfortunately), then it makes sense to use it to extract the very best out of your lenses. The comment about using the environment is good advice. A bird photo is enhanced by its placement within the environment. Perhaps my wren shot could have had better background, but I didn't choose where he appeared. :)
11zszm.jpg
 
All good advice, I seems I'm either gonna be very lucky or patient to get a good shot.

I'm not sure I could spent the extra to get a much bigger lens to dedicate to small birds.

I've spent around £1500 on my 50D & Canon lens's.

I need much more practice & I love this site for honest advice.

Shot this today while having a sly tens mins to myself.

UglyDuckling.jpg
[/IMG]

Mick
 
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