What does 'at 30mm' mean when printed next to pictures?

CotswoldsRetreat

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Hi all

As you can probably tell from the subject title I am very much a beginner at photography.

I have recently moved from a Point-and-Shoot Canon camera and purchased a Panasonic DMC-FZ200 and 'Understanding Exposure' by Bryan Peterson and while I am making progress in improving my photography knowledge the learning curve is still steep!

In Byran's book - and others for that matter - I see the following example details listed:

f/5.6 for 1/500 sec 35-70mm at 35mm

or


f/32 for 1/15 sec 75-300 lens at 130mm

The aperture and shutter I understand but I am not fully understanding the 35-70mm at 35mm or the 75-300 lens at 130mm

The DMC-FZ200 has a 25-600mm lens and I assume that when fully retract then the length is 25mm and when fully zoomed it will be 600mm - or is it?

When I am zooming out how do I find out how far I have zoomed? I am sure if the FZ200 can tell me so how do other photographers know?

On the FZ200 is the 25-600mm referring to the focal length?

Hope all that makes sense and if anyone can shed light on my bolded queries I would be very grateful.
 
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CotswoldsRetreat

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In a follow up to my earlier post I understand that the focal length spec of the FZ200 is:

f = 4.5 - 108mm (25 - 600mm in 35mm equivalent)

I have no idea what that means or how I should take this into account when taking photos.

Hope someone can explain or point me in the right direction to a website that might help.
 

ronlane

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Welcome to the site. The 25-600mm is the focal range of the zoom of your camera. Bryan P is referring to which lens he is using. The @30mm is the focal length used for that specific picture. For instance, I shoot a canon t3i with a 70-200mm f/2.8L. I can shoot it at any range from 70mm to 200mm.

The f 4.5 is the apeture that was used and the 108mm is the focal length.

That is a good book you are reading and is very helpful, but I think you need to get some more basic understanding of the exposure triangle for some very basic terminology.
 
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CotswoldsRetreat

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Hi Ron

Many thanks for your reply - much appreciated.

With respect to the exposure triangle I think I have a good handle on how aperture - shutter - and ISO are related to obtain good exposure.

Now that you have clarified that it is the focal length that I have been referring to what I am struggling to come to terms with is how do I know what focal length I am shooting at on the FZ200.

As it is a fixed lens camera without any measurements on the barrel I do not know what the focal length is when I am taking my photo. Maybe I don't need to know - perhaps I just zoom in and out until I like the composition and take the photo.

Perhaps there is data within the RAW file that software can look at to tell me what the focal length was at the time I took the photo - or can the FZ200 tell me on the LCD display. If it can I haven't found out how :)
 

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35-70mm at 35mm

This means the photographer used a 35-70mm zoom lens, and shot the picture at 35mm. The zoom lens gives you a range of focal lengths to choose from, and they are telling you which one they used.

To understand the focal length equivalent, you need to understand that different digital cameras use different sized sensors (which turn light into the electrical signals which make the digital image). Different sized sensors paired with the same focal length lens change the field of view and the "look" of a photo. The "equivalent focal length" is a standard used to normalize the "look" of a photo as it would come out of a 35mm film or full-size digital camera. If you took a photo with your camera at 4.5mm actual focal length, and compared it to a photo from a 35mm film camera at 25mm, the photos would look the same.

I suggest you do some google searches for "crop sensor" and "equivalent focal length" and do a little more reading on this.
 

Low_Sky

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Hi Ron

Many thanks for your reply - much appreciated.

With respect to the exposure triangle I think I have a good handle on how aperture - shutter - and ISO are related to obtain good exposure.

Now that you have clarified that it is the focal length that I have been referring to what I am struggling to come to terms with is how do I know what focal length I am shooting at on the FZ200.

As it is a fixed lens camera without any measurements on the barrel I do not know what the focal length is when I am taking my photo. Maybe I don't need to know - perhaps I just zoom in and out until I like the composition and take the photo.

Perhaps there is data within the RAW file that software can look at to tell me what the focal length was at the time I took the photo - or can the FZ200 tell me on the LCD display. If it can I haven't found out how :)

Without focal lengths marked on the camera, you'll just have to play around with it to get familiar with the field of view that you can get across the zoom range of your camera. When you look at the EXIF data, it will give you the actual focal length. To get the equivalent focal length, you need to multiply that by the crop factor of your camera (5.56). Since you were given the actual and equivalent focal length range, crop factor is easy. 600mm/108mm = 5.56 crop factor.
 

ronlane

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As it is a fixed lens camera without any measurements on the barrel I do not know what the focal length is when I am taking my photo. Maybe I don't need to know - perhaps I just zoom in and out until I like the composition and take the photo.

This is correct on tha P&S. If you have a way to look at the exif data after taking the photos, you can start to learn what zoom is what focal length. But you are right, just zoom in or out to get the exposure that you want and take the shot.
 

KmH

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In a follow up to my earlier post I understand that the focal length spec of the FZ200 is:

f = 4.5 - 108mm (25 - 600mm in 35mm equivalent)
The 35 mm equivelent note can be a confusing aspect of camera/lens marketing that many new to photography have difficulty coming to grips with.

The lens on your camera has a focal length range of 4.5-108 mm.
Your Panasonic has the smallest image sensor they make - 1/2.3" (6.17 x 4.55 mm) - and has a crop factor of 5.62x. Crop factor - Wikipedia, the free encyclopedia
A standard 35 mm image sensor is 36 mm x 26 mm, and has no crop factor.
Note that 4.5 mm times 5.62 = 25.29 mm which they have rounded down to 25 mm, and 108 mm times 5.62 = 606.96 mm which they have rounded down to 600 mm.

Image sensor format - Wikipedia, the free encyclopedia

The 25-600mm is the focal range of the zoom of your camera.
The focal length range does not change and is always 4.5 mm to 108 mm.
The Panasonic's zoom lens is 4.5 mm - 108 mm, but it delivers a field-of-view (FoV) equivelent to a 25-600 mm zoom lens mounted on a camera that has a full size 35 mm image sensor (or film).

Digital Camera Sensor Sizes: How it Influences Your Photography
Understanding Camera Lenses
Camera Lens Quality: MTF, Resolution & Contrast
 

timor

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CotswoldsRetreat

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To everyone who has replied please accept my thanks. To save cluttering the threat I will not quote individual posts and reply back individually - which I hope you will accept as good netiquette :)

I've been given some good advice and will ensure to follow it up - particularly the links to other resources.

As KmH pointed out the crop factor and image sensor format is confusing for us beginners so I will work on figuring these two out as soon as I can.
 

EDL

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To everyone who has replied please accept my thanks. To save cluttering the threat I will not quote individual posts and reply back individually - which I hope you will accept as good netiquette :)

I've been given some good advice and will ensure to follow it up - particularly the links to other resources.

As KmH pointed out the crop factor and image sensor format is confusing for us beginners so I will work on figuring these two out as soon as I can.

Crop factor is only really relevant if you want to compare your field of view to what a full frame sensor would see.

35mm became a standard in film SLR's. Modern digital camera sensors are compared to this standard and that's how we get a crop factor. The physical sensor itself, if it is smaller than a 35mm film frame is a crop sensor. A full frame digital means the sensor is the same physical size as a 35mm film frame.

The size differences in the sensor will determine how much (in terms of physical area) of the image a lens sees that it will capture, but again, this is only relevant if you are comparing it to a full frame/35mm frame.

It means nothing to the individual crop sensor camera as it will see what it sees.

For example, my camera is a 1.6x crop factor. If I put a 200mm telephoto lens on it, a full frame camera would have to use a 320mm lens to get the exact same field of view. Since your camera has a crop factor of 5.62, in your case you'd need a focal length of 57mm.

And...to add to the confusion, it's really, really only useful to any real degree if your camera has changeable lenses.

I wouldn't worry about it. Just zoom, compose and shoot. The focal length is irrelevant.
 

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